picocli - a mighty tiny command line interface

Every main method deserves picocli!

1. Introduction

Picocli is a one-file Java framework for parsing command line arguments and generating polished, easily tailored usage help messages. With colors.

Screenshot of usage help with Ansi codes enabled

Now in BETA: command line autocompletion. (Comments, bug reports, pull requests welcome!)

A distinguishing feature of picocli is how it aims to let users run picocli-based applications without requiring picocli as an external dependency: all the source code lives in a single file, to encourage application authors to include it in source form.

How it works: annotate your class and picocli initializes it from the command line arguments, converting the input to strongly typed values in the fields of your class.

import picocli.CommandLine.Option;
import picocli.CommandLine.Parameters;
import java.io.File;

public class Example {
    @Option(names = { "-v", "--verbose" }, description = "Be verbose.")
    private boolean verbose = false;

    @Parameters(arity = "1..*", paramLabel = "FILE", description = "File(s) to process.")
    private File[] inputFiles;
    ...
}

Then invoke CommandLine.parse or CommandLine.populateCommand with the command line parameters and an object you want to initialize.

String[] args = { "-v", "inputFile1", "inputFile2" };
Example app = CommandLine.populateCommand(new Example(), args);
assert  app.verbose;
assert  app.inputFiles != null && app.inputFiles.length == 2;

Here is a small example application:

@Command(name = "checksum", description = "Prints the checksum (MD5 by default) of a file to STDOUT.")
class CheckSum {

    @Parameters(index = "0", description = "The file whose checksum to calculate.")
    private File file;

    @Option(names = {"-a", "--algorithm"}, description = "MD5, SHA-1, SHA-256, ...")
    private String algorithm = "MD5";

    @Option(names = {"-h", "--help"}, usageHelp = true, description = "Show this help message and exit.")
    private boolean helpRequested;

    public static void main(String[] args) throws Exception {
        CheckSum checkSum = new CheckSum();
        try {
            new CommandLine(checkSum).parse(args);
        } catch (ParameterException ex) { // handle invalid input
            System.err.println(ex.getMessage());
            CommandLine.usage(checkSum, System.err);
            return;
        }
        checkSum.call();
    }

    public void call() throws Exception {
        if (helpRequested) {
            CommandLine.usage(this, System.err);
            return;
        }
        byte[] digest = MessageDigest.getInstance(algorithm).digest(readBytes(file));
        print(digest, System.out);
    }

    byte[] readBytes(File f) throws IOException {...}
    void print(byte[] digest, PrintStream out) {...}
}

You may also be interested in the CommandLine.run and CommandLine.call convenience methods for parsing that take care of handling invalid command line arguments.

2. Options and Parameters

Command line arguments can be separated into options and positional parameters. Options have a name, positional parameters are the values that follow the options.

Example command with annotated @Option and @Parameters

Picocli has separate annotations for options and positional parameters.

2.1. Options

An option must have one or more names. Picocli lets you use any option name you want.

You may be interested in this list of common option names. Following these conventions may make your application more intuitive to use for experienced users.

The below example shows options with one or more names, options that take an option parameter, and a help option.

class Tar {
    @Option(names = "-c", description = "create a new archive")
    boolean create;

    @Option(names = { "-f", "--file" }, paramLabel = "ARCHIVE", description = "the archive file")
    File archive;

    @Parameters(paramLabel = "FILE", description = "one or more files to archive")
    File[] files;

    @Option(names = { "-h", "--help" }, usageHelp = true, description = "display a help message")
    private boolean helpRequested = false;
}

Picocli matches the option names to set the field values.

String[] args = { "-c", "--file", "result.tar", "file1.txt", "file2.txt" };
Tar tar = new Tar();
new CommandLine(tar).parse(args);

assert !tar.helpRequested;
assert  tar.create;
assert  tar.archive.equals(new File("result.tar"));
assert  Arrays.equals(tar.files, new File[] {new File("file1.txt"), new File("file2.txt")});

2.2. Short Options

Picocli supports POSIX clustered short options: one or more single-character options without option-arguments, followed by at most one option with an option-argument, can be grouped behind one '-' delimiter.

For example, given this annotated class:

class ClusteredShortOptions {
    @Option(names = "-a") boolean aaa;
    @Option(names = "-b") boolean bbb;
    @Option(names = "-c") boolean ccc;
    @Option(names = "-f") String  file;
}

The following command line arguments are all equivalent and parsing them will give the same result:

<command> -abcfInputFile.txt
<command> -abcf=InputFile.txt
<command> -abc -f=InputFile.txt
<command> -ab -cf=InputFile.txt
<command> -a -b -c -fInputFile.txt
<command> -a -b -c -f InputFile.txt
<command> -a -b -c -f=InputFile.txt
...

2.3. Positional Parameters

Positional parameters are the command line arguments following the options.

Use the (zero-based) index attribute to specify exactly which parameters to capture. Omitting the index attribute means the field captures all positional parameters. Array or collection fields can capture multiple values.

The index attribute accepts range values, so an annotation like @Parameters(index="2..4") captures the arguments at index 2, 3 and 4. Range values can be open-ended. For example, @Parameters(index="3..*") captures all arguments from index 3 and up.

For example:

class PositionalParameters {
    @Parameters(hidden = true)  // "hidden": don't show this parameter in usage help message
    List<String> allParameters; // no "index" attribute: captures _all_ arguments (as Strings)

    @Parameters(index = "0")    InetAddress host;
    @Parameters(index = "1")    int port;
    @Parameters(index = "2..*") File[] files;
}

Picocli initializes fields with the values at the specified index in the arguments array.

String[] args = { "localhost", "12345", "file1.txt", "file2.txt" };
PositionalParameters params = CommandLine.populateCommand(new PositionalParameters(), args);

assert params.host.getHostName().equals("localhost");
assert params.port == 12345;
assert Arrays.equals(params.files, new File[] {new File("file1.txt"), new File("file2.txt")});
assert params.allParameters.equals(Arrays.asList("localhost", "12345", "file1.txt", "file2.txt"));

See Strongly Typed Everything for which types are supported out of the box and how to add custom types.

2.4. Double dash (`--`)

When one of the command line arguments is just two dashes without any characters attached (--), picocli interprets all following arguments as positional parameters, even arguments that match an option name.

class DoubleDashDemo {
    @Option(names = "-v")     boolean verbose;
    @Option(names = "-files") List<String> files;
    @Parameters               List<String> params;
}

The -- clarifies which of the arguments are positional parameters:

String[] args = { "-v", "--", "-files", "file1", "file2" };
DoubleDashDemo demo = new DoubleDashDemo();
new CommandLine(demo).parse(args);

assert demo.verbose;
assert demo.files == null;
assert demo.params.equals(Arrays.asList("-files", "file1", "file2"));

3. Strongly Typed Everything

When command line options and positional parameters are mapped to the annotated fields, the text value is converted to the type of the annotated field.

3.1. Built-in Types

Out of the box, picocli can convert command line argument strings to:

any Java primitive type or their wrapper
any enum
BigDecimal, BigInteger
Charset
File
InetAddress
regex Pattern
String, StringBuilder, CharSequence
java.sql.Time (for values in any of the "HH:mm", "HH:mm:ss", "HH:mm:ss.SSS", or "HH:mm:ss,SSS" formats)
java.util.Date (for values in "yyyy-MM-dd" format)
URL, URI
UUID

3.2. Custom Type Converters

Custom converters need to implement the picocli.CommandLine.ITypeConverter interface:

public interface ITypeConverter<K> {
    /**
     * Converts the specified command line argument value to some domain object.
     * @param value the command line argument String value
     * @return the resulting domain object
     * @throws Exception an exception detailing what went wrong during the conversion
     */
    K convert(String value) throws Exception;
}

Custom type converters can be registered with the CommandLine.registerConverter(Class<K> cls, ITypeConverter<K> converter) method.

Picocli works with Java 5 and higher, so it does not have default converters for Java 8 types like Path or Duration. Lambdas make it easy to register custom converters for these types:

commandLine.registerConverter(java.nio.file.Path.class, s -> java.nio.file.Paths.get(s));
commandLine.registerConverter(java.time.Duration.class, s -> java.time.Duration.parse(s));

After registering custom converters, call the parse(String…) method on the CommandLine instance where the converters are registered. (The static populateCommand method cannot be used.) For example:

class App {
    @Parameters Path path;
    @Option(names = "-d") Duration duration;
}

App app = new App();
CommandLine commandLine = new CommandLine(app)
        .registerConverter(Path.class,     s -> Paths.get(s))
        .registerConverter(Duration.class, s -> Duration.parse(s));

commandLine.parse("-d", "PT15M", "file1.txt");
assert app.path.equals(Paths.get("file1.txt"));
assert app.duration.equals(Duration.parse("PT15M"));

Note on subcommands: the specified converter will be registered with the CommandLine object and all subcommands (and nested sub-subcommands) that were added before the converter was registered. Subcommands added later will not have the converter added automatically. To ensure a custom type converter is available to all subcommands, register the type converter last, after adding subcommands.

3.3. Arrays, Collections, Maps

With array fields picocli uses reflection to discover the array element type, but with collections, Java type erasure means picocli cannot find out the generic type of the collection. For non-String collections, use the type attribute to specify what type to convert the command line arguments to.

3.3.1. Arrays and Collections

Multiple parameters can be captured together in a single array or Collection field. When using a collection, use the type attribute to specify the collection element type. For example:

import java.util.regex.Pattern;
import java.io.File;

class Convert {
    @Option(names = "-patterns"); // no `type` annotation attribute needed
    Pattern[] patterns;           // for array fields

    @Parameters(type = File.class)
    List<File> files;
}

String[] args = { "-patterns", "a*b", "[a-e][i-u]", "--", "file1.txt", "file2.txt" };
Convert convert = CommandLine.populateCommand(new Convert(), args);

// convert.patterns now has two Pattern objects
// convert.files now has two File objects

If a collection is returned from a type converter, the contents of the collection are added to the field, not the collection itself.

3.3.2. Maps

Since 1.0.0, picocli supports Map fields similar to Java’s system properties -Dkey=value or Gradle’s project properties -Pmyprop=myvalue.

Map fields may have any type for their key and value. Use the type attribute to specify the both the key type and the value type. For example:

import java.net.InetAddress;
import java.net.Proxy.Type;
import java.util.concurrent.TimeUnit;

class MapDemo {
    @Option(names = {"-p", "--proxyHost"}, type = {Proxy.Type.class, InetAddress.class});
    Map<Proxy.Type, InetAddress> proxies;

    @Option(names = {"-u", "--timeUnit"}, type = {TimeUnit.class, Long.class});
    Map<TimeUnit, Long> timeout;
}

Map options may be specified multiple times with different key-value pairs. (See <<#default-arity,arity>>.)

<command> -p HTTP=123.123.123.123 --proxyHost SOCKS=212.212.212.212
<command> -uDAYS=3 -u HOURS=23 -u=MINUTES=59 --timeUnit=SECONDS=13

On the command line, the key and the value must be separated by a = character.

4. Multiple Values

Arity is the number of parameters that will be consumed by an option.

4.1. Default Arity

The default arity value of an @Option or @Parameters field depends on its type.

Boolean fields: the default arity is 0 (consume zero parameters) the field is toggled to its logical negative when the option name is recognized. (You can change this.)
Single-valued types like int, String, File: arity is 1 (consume one parameter). Omitting the option parameter results in a ParameterException: "Missing required parameter for field '<field-name>'".
Multi-valued types like arrays, collections or maps: consume from zero up to all available parameters (until encountering another option or subcommand).

4.2. Arity

When an option or parameters field has a type that can hold multiple values (an array or a collection), the arity attribute lets you control exactly how many parameters to capture.

The arity attribute can specify an exact number of required parameters, or a range with a minimum and a maximum number of parameters. The maximum can be an exact upper bound, or it can be "*" to denote any number of parameters. For example:

class ArityDemo {
    @Parameters(arity = "3", descriptions = "exactly three Files")
    File[] files;

    @Option(names = "-f", arity = "2..4", description = "two to four floating point numbers")
    double[] doubles;

    @Option(names = "-s", arity = "1..*", description = "at least one string")
    String[] strings;
}

A MissingParameterException is thrown when fewer than the miminum number of parameters is specified on the command line.

Once the minimum number of parameters is consumed, picocli will check each subsequent command line argument to see whether it is an additional parameter, or a new option. For example:

ArityDemo -s A B C -f 1.0 2.0 3.0

Option -s has arity "1..*" but instead of consuming all parameters, the last three parameters will be recognized as belonging to the -f option.

4.3. Split Regex

Options and parameters may also specify a split regular expression used to split each option parameter into smaller substrings. Each of these strings is converted to the type of the collection or array. See Arrays and Collections.

@Option(names = "-option", split = ",")
int[] values;

Command line arguments like the following are interpreted as three int values instead of a single string:

-option 111,222,333

Similarly for Maps:

@Option(names = "-fix", split = "\\|", type = {Integer.class, String.class})
Map<Integer,String> message;

With the above option, command line arguments like the following are interpreted as a set of key-value pairs instead of a single string:

-fix 8=FIX.4.4|9=69|35=A|49=MBT|56=TargetCompID|34=9|52=20130625-04:05:32.682|98=0|108=30|10=052

4.4. Multiple Occurrences

Users may also specify the same option multiple times. For example:

-option 111 -option 222 -option 333

Each value is appended to the array or collection.

5. Required Arguments

5.1. Required Options

Options can be marked required to make it mandatory for the user to specify them on the command line. When a required option is not specified, a MissingParameterException is thrown from the parse method. For example:

class MandatoryOption {
    @Option(names = "-n", required = true, description = "mandatory number")
    int number;

    @Parameters
    File[] files;
}

The following command line arguments would result in an exception complaining that number is missing:

// invalid: missing option -n
<command> file1 file2 file3

The following command line arguments would be accepted:

// valid: required option -n has a value
<command> -n 123 file1 file2 file3

5.2. Required Parameters

Use the arity attribute to make @Parameters mandatory:

class BothOptionAndParametersMandatory {
    @Parameters(arity = "1..*", descriptions = "at least one File")
    File[] files;

    @Option(names = "-n", required = true, description = "mandatory number")
    int number;
}

The following command line arguments would result in an exception complaining that files are missing:

// invalid: missing file parameters
<command> -n 123

The following command line arguments would be accepted:

// valid: both required fields have a value
<command> -n 123 file1

6. Help Options

Options with the attribute help = true are special: if one of the command line arguments is a "help" option, picocli will stop parsing the remaining arguments and will not check for required options.

Picocli 0.9.8 introduces two new option attributes, versionHelp and usageHelp. These also stop validation to prevent "missing required option" errors, but are more specific and are preferred over the generic help attribute.

@Option(names = {"-V", "--version"}, versionHelp = true, description = "display version info")
boolean versionInfoRequested;

@Option(names = {"-h", "--help"}, usageHelp = true, description = "display this help message")
boolean usageHelpRequested;

Use these attributes for options that request the usage help message or version information to be shown on the console.

Picocli does not automatically print a help message. (This ticket explains why not; feedback is welcome.) It is the responsibility of the application to check the field and show the usage help message.

App app = CommandLine.populateCommand(new App(), args);
if (app.usageHelpRequested) {
   CommandLine.usage(new App(), System.err);
   return;
}

Since version 0.9.8, the CommandLine class offers two methods that allow external components to detect whether usage help or version information was requested (without inspecting the annotated domain object):

CommandLine.isUsageHelpRequested() returns true if the parser matched an option annotated with usageHelp=true
CommandLine.isVersionHelpRequested() returns true if the parser matched an option annotated with versionHelp=true

CommandLine commandLine = new CommandLine(new App());
commandLine.parse(args);
if (commandLine.isUsageHelpRequested()) {
   commandLine.usage(System.err);
   return;
} else if (commandLine.isVersionHelpRequested()) {
   commandLine.printVersionHelp(System.err);
   return;
}

7. Version Help

Since 0.9.8, applications can specify version information in the version attribute of the @Command annotation.

@Command(version = "1.0")
class VersionedCommand {
    @Option(names = { "-V", "--version" }, versionHelp = true,
            description = "print version information and exit")
    boolean versionRequested;
    ...

The CommandLine.printVersionHelp(PrintStream) method extracts the version information from this annotation and prints it to the specified PrintStream.

CommandLine commandLine = new CommandLine(new VersionedCommand());
commandLine.parse(args);
if (commandLine.isVersionHelpRequested()) {
    commandLine.printVersionHelp(System.err);
    return;
}

The version may specify multiple Strings. Each will be printed on a separate line.

@Command(version = { "Versioned Command 1.0", "Build 12345", "(c) 2017" })
class VersionedCommand { ... }

The CommandLine.printVersionHelp(PrintStream) method will print the above as:

Versioned Command 1.0
Build 12345
(c) 2017

The version strings may contain markup to show ANSI styles and colors. For example:

@Command(version = {
        "@|yellow Versioned Command 1.0|@",
        "@|blue Build 12345|@",
        "@|red,bg(white) (c) 2017|@" })
class VersionedCommand { ... }

The markup will be rendered as ANSI escape codes on supported systems.

Screenshot of version information containing markup with Ansi styles and colors

From 1.0.0, the version may contain format specifiers:

@Command(version = {
    "Versioned Command 1.0",
    "Build %1$s",
    "(c) 2017, licensed to %2$s" })
class VersionedCommand { ... }

Format argument values can be passed to the printVersionHelp method:

String[] args = {"1234", System.getProperty("user.name")};
new CommandLine(new VersionedCommand())
    .printVersionHelp(System.err, Help.Ansi.AUTO, args);

8. Usage Help

8.1. Compact Example

A default picocli usage help message looks like this:

Usage: cat [-AbeEnstTuv] [--help] [--version] [FILE...]
Concatenate FILE(s), or standard input, to standard output.
      FILE                    Files whose contents to display
  -A, --show-all              equivalent to -vET
  -b, --number-nonblank       number nonempty output lines, overrides -n
  -e                          equivalent to -vET
  -E, --show-ends             display $ at end of each line
  -n, --number                number all output lines
  -s, --squeeze-blank         suppress repeated empty output lines
  -t                          equivalent to -vT
  -T, --show-tabs             display TAB characters as ^I
  -u                          (ignored)
  -v, --show-nonprinting      use ^ and M- notation, except for LDF and TAB
      --help                  display this help and exit
      --version               output version information and exit
Copyright(c) 2017

The usage help message is generated from annotation attributes, like below:

@Command(name = "cat", footer = "Copyright(c) 2017",
         description = "Concatenate FILE(s), or standard input, to standard output.")
class Cat {

  @Parameters(paramLabel = "FILE", description = "Files whose contents to display")
  List<File> files;

  @Option(names = "--help", usageHelp = true, description = "display this help and exit")
  boolean help;

  @Option(names = "-t",                 description = "equivalent to -vT")  boolean t;
  @Option(names = "-e",                 description = "equivalent to -vET") boolean e;
  @Option(names = {"-A", "--show-all"}, description = "equivalent to -vET") boolean all;

  // ...
}

8.2. Command Name

In the above example, the program name is taken from the name attribute of the Command annotation:

@Command(name = "cat")

Without a name attribute, picocli will show a generic <main class> in the synopsis:

Usage: <main class> [-AbeEnstTuv] [--help] [--version] [FILE...]

8.3. Parameter Labels

Non-boolean options require a value. The usage help should explain this, and picocli shows the option parameter in the synopsis and in the option list. By default, the field name is shown in < and > fish brackets. Use the paramLabel attribute to display a different name. For example:

Usage: <main class> [-f=FILE] [-n=<number>] NUM <host>
      NUM                     number param
      host                    the host parameter
  -f= FILE                    a file
  -n= <number>                a number option

Some annotated fields in the below example class have a paramLabel attribute and others don’t:

@Command()
class ParamLabels {
    @Option(names = "-f",    paramLabel = "FILE", description = "a file")      File f;
    @Option(names = "-n",    description = "a number option")                  int number;
    @Parameters(index = "0", paramLabel = "NUM", description = "number param") int n;
    @Parameters(index = "1", description = "the host parameter")               InetAddress host;
}

For demonstration purposes the above example mixes the all-uppercase (e.g., NUM) style label and the fish bracket (e.g., <number>) style labels. For real applications, mixing these label styles should be avoided. An application should consistently use only one style.

8.4. Unsorted Option List

By default the options list displays options in alphabetical order. Use the sortOptions = false attribute to display options in the order they are declared in your class.

@Command(sortOptions = false)

8.5. Abbreviated Synopsis

If a command is very complex and has many options, it is sometimes desirable to suppress details from the synopsis with the abbreviateSynopsis attribute. For example:

Usage: <main class> [OPTIONS] [<files>...]

Note that the positional parameters are not abbreviated.

@CommandLine.Command(abbreviateSynopsis = true)
class App {
    @Parameters File[] files;
    @Option(names = {"--count", "-c"}) int count;
    ....
}

8.6. Custom Synopsis

For even more control of the synopsis, use the customSynopsis attribute to specify one or more synopsis lines. For example:

Usage: ln [OPTION]... [-T] TARGET LINK_NAME   (1st form)
  or:  ln [OPTION]... TARGET                  (2nd form)
  or:  ln [OPTION]... TARGET... DIRECTORY     (3rd form)
  or:  ln [OPTION]... -t DIRECTORY TARGET...  (4th form)

To produce a synopsis like the above, specify the literal text in the customSynopsis attribute:

@Command(synopsisHeading = "", customSynopsis = {
        "Usage: ln [OPTION]... [-T] TARGET LINK_NAME   (1st form)",
        "  or:  ln [OPTION]... TARGET                  (2nd form)",
        "  or:  ln [OPTION]... TARGET... DIRECTORY     (3rd form)",
        "  or:  ln [OPTION]... -t DIRECTORY TARGET...  (4th form)",
})
class Ln { ... }

8.7. Header and Footer

The header will be shown at the top of the usage help message (before the synopsis). The first header line is also the line shown in the subcommand list if your command has subcommands (see Usage Help for Subcommands).

Use the footer attribute to specify one or more lines to show below the generated usage help message. Each element of the attribute String array is displayed on a separate line.

The headerHeading and footerHeading may contain format specifiers. See Section Headings.

8.8. Section Headings

Section headers can be used to make usage message layout appear more spacious. Section headings may contain embedded line separator (%n) format specifiers:

@CommandLine.Command(name = "git-commit",
        sortOptions = false,
        headerHeading = "Usage:%n%n",
        synopsisHeading = "%n",
        descriptionHeading = "%nDescription:%n%n",
        parameterListHeading = "%nParameters:%n",
        optionListHeading = "%nOptions:%n",
        header = "Record changes to the repository.",
        description = "Stores the current contents of the index in a new commit " +
                "along with a log message from the user describing the changes.")
class GitCommit { ... }

The usage help message generated from this class is shown below in Expanded Example.

8.9. Expanded Example

The below example demonstrates what a customized usage message can look like. Note how section headings with line separators can create a more spacious usage message, and also that options are listed in declaration order (instead of in alphabetic order).

Usage:

Record changes to the repository.

git-commit [-ap] [--fixup=<commit>] [--squash=<commit>] [-c=<commit>]
           [-C=<commit>] [-F=<file>] [-m[=<msg>...]] [<files>...]

Description:

Stores the current contents of the index in a new commit along with a log
message from the user describing the changes.

Parameters:
      <files>                 the files to commit

Options:
  -a, --all                   Tell the command to automatically stage files
                                that have been modified and deleted, but new
                                files you have not told Git about are not
                                affected.
  -p, --patch                 Use the interactive patch selection interface to
                                chose which changes to commit
  -C, --reuse-message=<commit>
                              Take an existing commit object, and reuse the log
                                message and the authorship information
                                (including the timestamp) when creating the
                                commit.
  -c, --reedit-message=<commit>
                              Like -C, but with -c the editor is invoked, so
                                that the user canfurther edit the commit
                                message.
      --fixup=<commit>        Construct a commit message for use with rebase
                                --autosquash.
      --squash=<commit>        Construct a commit message for use with rebase
                                --autosquash. The commitmessage subject line is
                                taken from the specified commit with a prefix
                                of "squash! ". Can be used with additional
                                commit message options (-m/-c/-C/-F).
  -F, --file=<file>           Take the commit message from the given file. Use
                                - to read the message from the standard input.
  -m, --message[=<msg>...]     Use the given <msg> as the commit message. If
                                multiple -m options are given, their values are
                                concatenated as separate paragraphs.

The annotated class that this usage help message is generated from is shown in Section Headings.

8.10. Option-Parameter Separators

The separator displayed between options and option parameters (= by default) in the synopsis and the option list can be configured with the separator attribute.

@Command(separator = " ")

the @Command(separator = " ") annotation also affects how picocli parses the command line. If you want the command parser to recognize one separator (= for example), but display a different separator (a space for example) in the usage help message, you need to programmatically configure the parser with the CommandLine.setSeparator method. See Custom Separators.

8.11. Hidden Options and Parameters

Options and Parameters with the hidden attribute set to true will not be shown in the usage help message. This is useful for example when a parameter at some index is captured into multiple fields: by default each of these fields would be shown in the usage message, which would be confusing for users.

For example, the all field below is annotated as hidden = true:

@Command()
class App {
    @Parameters(index = "0",    description = "destination host")  InetAddress host;
    @Parameters(index = "1",    description = "destination port")  int port;
    @Parameters(index = "2..*", description = "files to transfer") String[] files;

    @Parameters(hidden = true) String[] all;
}

The above will generate the following usage help message, where the all field is not shown:

Usage: <main class> <host> <port> [<files>...]
      host                    destination host
      port                    destination port
      files                   files to transfer

8.12. Show Default Values

Use the showDefaultValues = true attribute to append the default value of the options and positional parameters to the description column. Picocli uses reflection to get the default values from the annotated fields. For example:

@Command(showDefaultValues = true)
class DefaultValues {
    @Option(names = {"-f", "--file"}, description = "the file to use")
    File file = new File("config.xml");
}

CommandLine.usage(new DefaultValues(), System.out);

This produces the following usage help:

Usage: <main class> -f=<file>
  -f, --file=<file>           the file to use
                              Default: config.xml

8.13. Required-Option Marker

Required options can be marked in the option list by the character specified with the requiredOptionMarker attribute. By default options are not marked because the synopsis shows users which options are required and which are optional. This feature may be useful in combination with abbreviatedSynopsis. For example:

@Command(requiredOptionMarker = '*', abbreviateSynopsis = true)
class Example {
    @Option(names = {"-a", "--alpha"}, description = "optional alpha") String alpha;
    @Option(names = {"-b", "--beta"}, required = true, description = "mandatory beta") String beta;
}

Produces the following usage help message:

Usage: <main class> [OPTIONS]
  -a, --alpha=<alpha>         optional alpha
* -b, --beta=<beta>           mandatory beta

9. ANSI Colors and Styles

9.1. Colorized Example

Below shows the same usage help message as shown in Expanded Example, with ANSI escape codes enabled.

Screenshot of usage help with Ansi codes enabled

9.2. Usage Help with Styles and Colors

You can use colors and styles in the descriptions, header and footer of the usage help message.

Picocli supports a custom markup notation for mixing colors and styles in text, following a convention introduced by Jansi, where @| starts a styled section, and |@ ends it. Immediately following the @| is a comma-separated list of colors and styles, so @|STYLE1[,STYLE2]… text|@. For example:

@Command(description = "Custom @|bold,underline styles|@ and @|fg(red) colors|@.")

Description with Ansi styles and colors

Table 1. Pre-defined styles and colors that can be used in descriptions and headers using the `@|STYLE1[,STYLE2]… text|@` notation
Pre-defined Styles	Pre-defined Colors
bold	black
faint	red
underline	green
italic	yellow
blink	blue
reverse	magenta
reset	cyan
	white

Colors are applied as foreground colors by default. You can set background colors by specifying bg(<color>). For example, @|bg(red) text with red background|@. Similarly, fg(<color>) explicitly sets the foreground color.

The example below shows how this markup can be used to add colors and styles to the headings and descriptions of a usage help message:

@CommandLine.Command(name = "git-commit",
        sortOptions = false,
        headerHeading = "@|bold,underline Usage|@:%n%n",
        synopsisHeading = "%n",
        descriptionHeading = "%n@|bold,underline Description|@:%n%n",
        parameterListHeading = "%n@|bold,underline Parameters|@:%n",
        optionListHeading = "%n@|bold,underline Options|@:%n",
        header = "Record changes to the repository.",
        description = "Stores the current contents of the index in a new commit " +
                "along with a log message from the user describing the changes.")
class GitCommit { ... }

9.3. More Colors

Most terminals support a 256 color indexed palette:

0x00-0x07:  standard colors (the named colors)
0x08-0x0F:  high intensity colors (often similar to named colors + bold style)
0x10-0xE7:  6 × 6 × 6 cube (216 colors): 16 + 36 × r + 6 × g + b (0 ≤ r, g, b ≤ 5)
0xE8-0xFF:  grayscale from black to white in 24 steps

Colors from the 256 color palette can be specified by their index values or by their RGB components. RGB components must be separated by a semicolon ; and each component must be between 0 and 5, inclusive.

For example, @|bg(0;5;0) text with red=0, green=5, blue=0 background|@, or @|fg(46) the same color by index, as foreground color|@.

256 color indexed palette

9.4. Configuring Fixed Elements

9.4.1. Color Scheme

Picocli uses a default color scheme for options, parameters and commands. There are no annotations to modify this color scheme, but it can be changed programmatically.

The below code snippet shows how a custom color scheme can be specified to configure the usage help message style:

// see also CommandLine.Help.defaultColorScheme()
ColorScheme colorScheme = new ColorScheme()
        .commands    (Style.bold, Style.underline)    // combine multiple styles
        .options     (Style.fg_yellow)                // yellow foreground color
        .parameters  (Style.fg_yellow)
        .optionParams(Style.italic);

CommandLine.usage(annotatedObject, System.out, colorScheme);
...

9.4.2. Color Scheme Overrides

The following system properties override the color scheme styles. This allows end users to adjust for their individual terminal color setup.

System Properties to Override the Color Scheme

picocli.color.commands
picocli.color.options
picocli.color.parameters
picocli.color.optionParams

For example:

java -Dpicocli.color.options=blink,blue -Dpicocli.color.parameters=reverse com.app.Main

System property values may specify multiple comma separated styles.

9.5. Supported Platforms

Picocli will only emit ANSI escape codes on supported platforms.

9.5.1. Unix and Linux

Most Unix and Linux platforms support ANSI colors natively. On Windows, when picocli detects it is running under a Unix variant like Cygwin or MSYS(2) on Windows it will display ANSI colors and styles, otherwise it will not emit ANSI codes.

9.5.2. Windows

Starting from Windows 10 the Windows console supports ANSI escape sequences, but they may need to be enabled.

For Windows version below 10, the Windows command console doesn’t support output coloring by default. One option is to install either Cmder, ConEmu, ANSICON or Mintty (used by default in GitBash and Cygwin) to add coloring support to their Windows command console.

Another option is to use Jansi in your application. For example:

import org.fusesource.jansi.AnsiConsole;
...
public static void main(String[] args) {
    AnsiConsole.systemInstall(); // Jansi magic
    CommandLine.run(new WindowsJansiDemo(), System.err, Ansi.ON, args);
    AnsiConsole.systemUninstall();
}

None of the above is mandatory. If not supported, picocli will simply not emit ANSI escape codes, and everything will work without colors.

9.6. Forcing ANSI On/Off

You can force picocli to either always use ANSI codes or never use ANSI codes regardless of the platform:

Setting system property picocli.ansi to true forces picocli to use ANSI codes; setting picocli.ansi to false forces picocli to not use ANSI codes. This may be a useful facility for users of your command line application.
You can decide to force disable or force enable ANSI escape codes programmatically by specifying Ansi.ON or Ansi.OFF when invoking CommandLine.usage. This overrides the value of system property picocli.ansi. For example:

import picocli.CommandLine.Help.Ansi;

App app = CommandLine.usage(new App(), System.out, Ansi.OFF, args);

10. Usage Help API

For further customization of the usage help message, picocli has a Help API. The Help class provides a number of high-level operations, and a set of components like Layout, TextTable, IOptionRenderer, etc., that can be used to build custom help messages. Details of the Help API are out of scope for this document, but the following sections give some idea of what is possible.

10.1. Reordering Sections

One thing you may want to do is reorder sections of the usage message or add custom sections.

To reorder sections, you need to use the CommandLine.Help class directly. The CommandLine.usage method implementation looks like this:

Help help = new Help(annotatedObject);
StringBuilder sb = new StringBuilder()
        .append(help.headerHeading())
        .append(help.header())
        .append(help.synopsisHeading())      //e.g. Usage:
        .append(help.synopsis())             //e.g. <main> [OPTIONS] [ARGUMENTS]
        .append(help.descriptionHeading())   //e.g. %nDescription:%n%n
        .append(help.description())          //e.g. "application description"
        .append(help.parameterListHeading()) //e.g. %nPositional parameters:%n%n
        .append(help.parameterList())        //e.g. [FILE...] the files to convert
        .append(help.optionListHeading())    //e.g. %nOptions:%n%n
        .append(help.optionList())           //e.g. -h, --help   displays this help
        .append(help.commandListHeading())   //e.g. %nCommands:%n%n
        .append(help.commandList())          //e.g.    add       adds a to b
        .append(help.footerHeading())
        .append(help.footer());

In your application, instead of calling CommandLine.usage(new MainClass(), System.err), you can alter the above code to, for example, list subcommands first, then global options and finally the parameters.

10.2. Custom Layout

Picocli also supports unconventional option list layouts. An example of an unconventional layout is the zip application, which shows multiple options per row:

CommandLine.usage(new ZipHelpDemo(), System.out);

Copyright (c) 1990-2008 Info-ZIP - Type 'zip "-L"' for software license.
Zip 3.0 (July 5th 2008). Command:
zip [-options] [-b path] [-t mmddyyyy] [-n suffixes] [zipfile list] [-xi list]
  The default action is to add or replace zipfile entries from list, which
  can include the special name - to compress standard input.
  If zipfile and list are omitted, zip compresses stdin to stdout.
  -f   freshen: only changed files  -u   update: only changed or new files
  -d   delete entries in zipfile    -m   move into zipfile (delete OS files)
  -r   recurse into directories     -j   junk (don't record) directory names
  -0   store only                   -l   convert LF to CR LF (-ll CR LF to LF)
  -1   compress faster              -9   compress better
  -q   quiet operation              -v   verbose operation/print version info
  -c   add one-line comments        -z   add zipfile comment
  -@   read names from stdin        -o   make zipfile as old as latest entry
  -x   exclude the following names  -i   include only the following names
  -F   fix zipfile (-FF try harder) -D   do not add directory entries
  -A   adjust self-extracting exe   -J   junk zipfile prefix (unzipsfx)
  -T   test zipfile integrity       -X   eXclude eXtra file attributes
  -y   store symbolic links as the link instead of the referenced file
  -e   encrypt                      -n   don't compress these suffixes
  -h2  show more help

This can be achieved in picocli by subclassing the Help.Layout class. See the picocli tests for how to achieve this.

11. Subcommands

11.1. Registering Subcommands Programmatically

Subcommands can be registered with the CommandLine.addSubcommand method. You pass in the name of the command and the annotated object to populate with the subcommand options. The specified name is used by the parser to recognize subcommands in the command line arguments.

CommandLine commandLine = new CommandLine(new Git())
        .addSubcommand("status",   new GitStatus())
        .addSubcommand("commit",   new GitCommit())
        .addSubcommand("add",      new GitAdd())
        .addSubcommand("branch",   new GitBranch())
        .addSubcommand("checkout", new GitCheckout())
        .addSubcommand("clone",    new GitClone())
        .addSubcommand("diff",     new GitDiff())
        .addSubcommand("merge",    new GitMerge())
        .addSubcommand("push",     new GitPush())
        .addSubcommand("rebase",   new GitRebase())
        .addSubcommand("tag",      new GitTag());

It is strongly recommended that subcommands have a @Command annotation with name and description attributes.

Subcommands registered programmatically can have a @Command name attribute that is different from the command name they are registered with. The name attribute value is not used when parsing the command line but only in the usage help synopsis of the subcommand. For example, a git command line could be git commit -m "message", but the usage help for the commit subcommand could show Usage: git-commit <options>.

Note on custom type converters: custom type converters are registered only with the subcommands and nested sub-subcommands that were added before the custom type was registered. To ensure a custom type converter is available to all subcommands, register the type converter last, after adding subcommands.

11.2. Registering Subcommands Declaratively

From version 0.9.8, picocli supports registering subcommands declaratively with the @Command annotation’s subcommands attribute.

@Command(subcommands = {
    GitStatus.class,
    GitCommit.class,
    GitAdd.class,
    GitBranch.class,
    GitCheckout.class,
    GitClone.class,
    GitDiff.class,
    GitMerge.class,
    GitPush.class,
    GitRebase.class,
    GitTag.class
})
public class Git { ... }

The declared subcommands are automatically instantiated and added when the new CommandLine(new Git()) instance is constructed. The result is the same as if subcommands were added programmatically.

Subcommands referenced in a subcommands attribute must have a @Command annotation with a name attribute, or an exception is thrown from the CommandLine constructor. This name will be used both for generating usage help and for recognizing subcommands when parsing the command line.

Custom type converters registered on a CommandLine instance will apply to all subcommands that were declared on the main command with the subcommands annotation.

11.3. Parsing Subcommands

The CommandLine.parse method returns a List with the recognized commands. The main command (git in this example) is always the first element in the returned list.

CommandLine commandLine = new CommandLine(new Git());

// add subcommands (either programmatically or declaratively)
commandLine.addSubcommand("status",   new GitStatus())
           .addSubcommand("commit",   new GitCommit())
            ...

// use the parse method to get a List with matched commands
String[] args = { "--git-dir=/home/rpopma/picocli", "status", "-sbuno"};
List<CommandLine> parsed = commandLine.parse(args);
assert parsed.size() == 2 : "1 command and 1 subcommand found"

assert parsed.get(0).getCommand().getClass() == Git.class       : "main command"
assert parsed.get(1).getCommand().getClass() == GitStatus.class : "subcommand"

Your application needs to inspect this list to see what subcommand was invoked and take appropriate action. For example:

Git git = (Git) parsed.get(0).getCommand();
assert git.gitDir.equals(new File("/home/rpopma/picocli"));

GitStatus gitstatus = (GitStatus) parsed.get(1).getCommand();
assert  gitstatus.shortFormat              : "git status -s"
assert  gitstatus.branchInfo               : "git status -b"
assert !gitstatus.showIgnored              : "git status --showIgnored not specified"
assert  gitstatus.mode == GitStatusMode.no : "git status -u=no"

11.4. Usage Help for Subcommands

After registering subcommands, calling the commandLine.usage method will show a usage help message that includes all registered commands. For example:

CommandLine commandLine = new CommandLine(new Git());

// add subcommands (either programmatically or declaratively)
commandLine.addSubcommand("status",   new GitStatus());
...
commandLine.usage(System.out);

The usage help message shows the commands in the order they were registered:

Usage: git [-hV] [--git-dir=<gitDir>]
Git is a fast, scalable, distributed revision control system with an unusually
rich command set that provides both high-level operations and full access to
internals.
  -V, --version               Prints version information and exits
  -h, --help                  Prints this help message and exits
      --git-dir=<gitDir>      Set the path to the repository

Commands:

The most commonly used git commands are:
  status    Show the working tree status.
  commit    Record changes to the repository.
  add       Add file contents to the index.
  branch    List, create, or delete branches.
  checkout  Checkout a branch or paths to the working tree.
  clone     Clone a repository into a new directory.
  diff      Show changes between commits, commit and working tree, etc.
  merge     Join two or more development histories together.
  push      Update remote refs along with associated objects.
  rebase    Forward-port local commits to the updated upstream head.
  tag       Create, list, delete or verify a tag object signed with GPG.

The above usage help message is produced from the annotations on the class below:

@Command(name = "git", sortOptions = false,
        description = "Git is a fast, scalable, distributed revision control " +
                      "system with an unusually rich command set that provides both " +
                      "high-level operations and full access to internals.",
        commandListHeading = "%nCommands:%n%nThe most commonly used git commands are:%n")
class Git {
  @Option(names = {"-V", "--version"}, versionHelp = true,
          description = "Prints version information and exits")
  private boolean versionRequested;

  @Option(names = {"-h", "--help"}, usageHelp = true,
          description = "Prints this help message and exits")
  private boolean helpRequested;

  @Option(names = "--git-dir", description = "Set the path to the repository")
  private File gitDir;
}

The usage help message for each subcommand is produced by calling CommandLine.usage(new SubCommand(), out). For example, see Section Headings for an example subcommand (git-commit), which produces the help message shown in Expanded Example.

11.5. Nested sub-subcommands

The specified object can be an annotated object or a CommandLine instance with its own nested subcommands. For example:

CommandLine commandLine = new CommandLine(new MainCommand())
    .addSubcommand("cmd1",                 new ChildCommand1())
    .addSubcommand("cmd2",                 new ChildCommand2())
    .addSubcommand("cmd3", new CommandLine(new ChildCommand3())
        .addSubcommand("cmd3sub1",                 new GrandChild3Command1())
        .addSubcommand("cmd3sub2",                 new GrandChild3Command2())
        .addSubcommand("cmd3sub3", new CommandLine(new GrandChild3Command3())
            .addSubcommand("cmd3sub3sub1", new GreatGrandChild3Command3_1())
            .addSubcommand("cmd3sub3sub2", new GreatGrandChild3Command3_2())
        )
    );

Declaratively, subcommands can be nested by specifying the subcommands attribute on subcommand classes:

@Command(name = "main", subcommands = {
    ChildCommand1.class,
    ChildCommand2.class,
    ChildCommand3.class })
class MainCommand { }

@Command(name = "cmd3", subcommands = {
    GrandChild3Command1.class,
    GrandChild3Command2.class,
    GrandChild3Command3.class })
class ChildCommand3 { }

@Command(name = "cmd3sub3", subcommands = {
    GreatGrandChild3Command3_1.class,
    GreatGrandChild3Command3_2.class })
class GrandChild3Command3 { }
...

12. Tips & Tricks

12.1. Less Boilerplate

You can omit some of the boilerplate code from your application when the annotated object implements Runnable or Callable:

Before

Callable<Object> callable = null;
try {
    callable = CommandLine.populateCommand(annotatedObject, args);
} catch (Exception ex) {
    System.err.println(ex.getMessage());
    CommandLine.usage(annotatedObject, System.err);
    return null;
}
return callable.call();

After

Object result = CommandLine.call(new MyCallable(), System.err, args);

The CommandLine.call method returns the result of the Callable, or null if the command line options were invalid. An error message and a usage help message are printed when the command line options were invalid. Exceptions thrown from the Callable.call method are not caught by the CommandLine.call method.

When the annotated object implements Runnable, use the run method. For example:

CommandLine.run(new MyRunnable(), System.err, args);

Note that the CommandLine.call and CommandLine.run convenience methods cannot be used with subcommands.

12.2. Boolean Parameters

By default the value of a boolean field is toggled to its logical negative when the field’s option is specified on the command line.

It is possible to let end users explicitly specify "true" or "false" as a parameter for a boolean option by defining an explicit Arity attribute. A boolean option with arity = "0..1" accepts zero to one parameters, arity = "1" means the option must have one parameter. For example:

class BooleanOptionWithParameters {
    @Option(names = "-x", arity = "1", description = "1 mandatory parameter")
    boolean x;

    @Option(names = "-y", arity = "0..1", description = "min 0 and max 1 parameter")
    boolean y;
}

The following ways to invoke the program will be accepted (values are not case sensitive):

<command> -x true
<command> -x FALSE
<command> -x TRUE -y
<command> -x True -y False

But trying to specify the -x option without a parameter, or with a value other than "true" or "false" (case insensitive) will result in a ParameterException.

12.3. Hexadecimal Values

Numeric values are interpreted as decimal numbers by default. If you want picocli to be more flexible, you can register a custom type converter that delegates to the decode method to convert strings to numbers.

The decode method looks at the prefix to determine the radix, so numbers starting with 0x, 0X or # are interpreted as hexadecimal numbers, numbers starting with 0 are interpreted as octal numbers, and otherwise the number is interpreted as a decimal number.

Java 8-style lambdas:

new CommandLine(obj)
        .registerConverter(Byte.class,    s -> Byte::decode)
        .registerConverter(Byte.TYPE,     s -> Byte::decode)
        .registerConverter(Short.class,   s -> Short::decode)
        .registerConverter(Short.TYPE,    s -> Short::decode)
        .registerConverter(Integer.class, s -> Integer::decode)
        .registerConverter(Integer.TYPE,  s -> Integer::decode)
        .registerConverter(Long.class,    s -> Long::decode)
        .registerConverter(Long.TYPE,     s -> Long::decode);

In Java 5:

ITypeConverter<Integer> intConverter = new ITypeConverter<Integer>() {
    public Integer convert(String s) {
        return Integer.decode(s);
    }
};
commandLine.registerConverter(Integer.class, intConverter);
commandLine.registerConverter(Integer.TYPE,  intConverter);
...

12.4. Option-Parameter Separators

12.4.1. Default Separators

Options may take an option parameter (also called option-argument). For POSIX-style short options (like -f or -c), the option parameter may be attached to the option, or it may be separated by a space or the separator string (= by default). That is, all of the below are equivalent:

<command> -foutput.txt
<command> -f output.txt
<command> -f=output.txt

Long option names (like --file) must be separated from their option parameter by a space or the separator string (= by default). That is, the first two below examples are valid but the last example is invalid:

// valid (separator between --file and its parameter)
<command> --file output.txt
<command> --file=output.txt

// invalid (picocli will not recognize the --file option when attached to its parameter)
<command> --fileoutput.txt

12.4.2. Custom Separators

The separator string can be customized programmatically or declaratively.

Use the separator attribute of the @Command annotation to declaratively set a separator string:

@Command(separator = ":")  // declaratively set a separator
class OptionArg {
    @Option(names = { "-f", "--file" }) String file;
}

OptionArg optionArg = CommandLine.populateCommand(new OptionArg(), "-f:output.txt");
assert optionArg.file.equals("output.txt");

Declaratively set separators are used both when parsing and in the usage help message.

Alternatively, the separator string can be changed programmatically with the CommandLine.setSeparator(String separator) method. For example:

OptionArg optionArg     = new OptionArg();
CommandLine commandLine = new CommandLine(optionArg);

commandLine.setSeparator(":"); // programmatically set a separator
commandLine.parse("-f:output.txt");
assert optionArg.file.equals("output.txt");

Programmatically set separators are only used when parsing. Changing the value does not modify the usage help message.

12.5. Subclassing for Reuse

Picocli will walk the class hierarchy to check for annotations, so you can declare common @Options and @Command attributes on a superclass and override these fields or attributes on a subclass.

The below example shows how common options like help and version can be declared as fields in a superclass so they are available in all subclasses. Similarly, annotating the superclass with default @Command attributes means subclasses won’t need to set these attributes.

@Command(synopsisHeading      = "%nUsage:%n%n",
         descriptionHeading   = "%nDescription:%n%n",
         parameterListHeading = "%nParameters:%n%n",
         optionListHeading    = "%nOptions:%n%n",
         commandListHeading   = "%nCommands:%n%n")
public abstract class AbstractCommand {

    @Option(names = { "-h", "-?", "--help" }, usageHelp = true,
            description = "give this help list")
    protected boolean helpRequested;

    @Option(names = { "-V", "--version" }, versionHelp = true,
            description = "print program version")
    protected boolean versionRequested;
}

All commands that extend AbstractCommand support the --help and --version options, and generate a usage help message in the same spacious style. For example:

@Command(name        = "zip",
         header      = "Compresses the specified FILE(s).",
         description = "The default action is to add or replace zipfile entries from list, " +
                       "which can include the special name - to compress standard input.",
         footer      = "Copyright (c) 1990-2008 Info-ZIP - Type 'zip "-L"' for software license.")
public class ZipCommand extends AbstractCommand {
    @Option(names = { "-o", "--output" }, description = "output file to write to")
    private File output;

    @Parameter(paramLabel = "FILE", description = "FILEs to compress")
    private File[] files;
}

12.6. Best Practices for Command Line Interfaces

When designing your command line application, the GNU recommendations for command line interfaces and POSIX Utility Guidelines may be useful.

Generally, many applications use options for optional values and parameters for mandatory values. However, picocli lets you make options required if you want to, see Required Arguments.

13. Tracing

From version 1.0.0, picocli supports parser tracing to facilitate troubleshooting.

System property picocli.trace controls the trace level. Supported levels are OFF, WARN, INFO, and DEBUG. The default trace level is WARN.

Specifying system property -Dpicocli.trace without a value will set the trace level to INFO.

OFF: Suppresses all tracing including warnings.
WARN: Shows single-value options that were specified multiple times (when CommandLine.overwrittenOptionsAllowed is true), and command line arguments that could not be matched as an option or positional parameter (when CommandLine.unmatchedArgumentsAllowed is true).
INFO: Shows a high-level overview of what happens during command line parsing.
DEBUG: Shows details of the decisions made by the parser during command line parsing.

Example:

alias git='java -Dpicocli.trace -cp picocli-all.jar picocli.Demo$Git'
git --git-dir=/home/rpopma/picocli commit -m "Fixed typos" -- src1.java src2.java src3.java
unalias git

Output:

[picocli INFO] Parsing 8 command line args [--git-dir=/home/rpopma/picocli, commit, -m, "Fixed typos", --, src1.java, src2.java, src3.java]
[picocli INFO] Setting File field 'Git.gitDir' to '\home\rpopma\picocli' for option --git-dir
[picocli INFO] Adding [Fixed typos] to List<String> field 'GitCommit.message' for option -m
[picocli INFO] Found end-of-options delimiter '--'. Treating remainder as positional parameters.
[picocli INFO] Adding [src1.java] to List<String> field 'GitCommit.files' for args[0..*]
[picocli INFO] Adding [src2.java] to List<String> field 'GitCommit.files' for args[0..*]
[picocli INFO] Adding [src3.java] to List<String> field 'GitCommit.files' for args[0..*]

14. TAB Autocomplete

Picocli-based applications can now have command line completion in Bash or Zsh Unix shells. See the Autocomplete for Java Command Line Applications manual for how to generate an autocompletion script tailored to your application.

15. API Javadoc

Picocli API Javadoc can be found here.

16. GitHub Project

The GitHub project has the source code, tests, build scripts, etc.

Star or fork this project on GitHub if you like it! (Projects with many forks are easier to find on GitHub Search.)

17. Issue Tracker

Please use the Issue Tracker to report bugs or request features.

18. License

Picocli is licensed under the Apache License 2.0.

19. Releases

Previous versions are available from the GitHub project Releases.

20. Download

You can add picocli as an external dependency to your project, or you can include it as source. See the source code below. Copy and paste it into a file called CommandLine.java, add it to your project, and enjoy!

20.1. Gradle

compile 'info.picocli:picocli:1.0.0-SNAPSHOT'

20.2. Maven

<dependency>
  <groupId>info.picocli</groupId>
  <artifactId>picocli</artifactId>
  <version>1.0.0-SNAPSHOT</version>
</dependency>

20.3. Scala SBT

libraryDependencies += "info.picocli" % "picocli" % "1.0.0-SNAPSHOT"

20.4. Ivy

<dependency org="info.picocli" name="picocli" rev="1.0.0-SNAPSHOT" />

20.5. Source

/*
   Copyright 2017 Remko Popma

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
 */
package picocli;

import java.awt.Point;
import java.io.File;
import java.io.PrintStream;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.Array;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.net.InetAddress;
import java.net.MalformedURLException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.nio.charset.Charset;
import java.sql.Time;
import java.text.BreakIterator;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.Set;
import java.util.SortedSet;
import java.util.Stack;
import java.util.TreeSet;
import java.util.UUID;
import java.util.concurrent.Callable;
import java.util.regex.Pattern;

import picocli.CommandLine.Help.Ansi.IStyle;
import picocli.CommandLine.Help.Ansi.Style;
import picocli.CommandLine.Help.Ansi.Text;

import static java.util.Locale.ENGLISH;
import static picocli.CommandLine.Help.Column.Overflow.SPAN;
import static picocli.CommandLine.Help.Column.Overflow.TRUNCATE;
import static picocli.CommandLine.Help.Column.Overflow.WRAP;

/**
 * <p>
 * CommandLine interpreter that uses reflection to initialize an annotated domain object with values obtained from the
 * command line arguments.
 * </p><h2>Example</h2>
 * <pre>import static picocli.CommandLine.*;
 *
 * &#064;Command(header = "Encrypt FILE(s), or standard input, to standard output or to the output file.")
 * public class Encrypt {
 *
 *     &#064;Parameters(type = File.class, description = "Any number of input files")
 *     private List&lt;File&gt; files = new ArrayList&lt;File&gt;();
 *
 *     &#064;Option(names = { "-o", "--out" }, description = "Output file (default: print to console)")
 *     private File outputFile;
 *
 *     &#064;Option(names = { "-v", "--verbose"}, description = "Verbosely list files processed")
 *     private boolean verbose;
 *
 *     &#064;Option(names = { "-h", "--help", "-?", "-help"}, help = true, description = "Display this help and exit")
 *     private boolean help;
 * }
 * </pre>
 * <p>
 * Use {@code CommandLine} to initialize a domain object as follows:
 * </p><pre>
 * public static void main(String... args) {
 *     try {
 *         Encrypt encrypt = CommandLine.populateCommand(new Encrypt(), args);
 *         if (encrypt.help) {
 *             CommandLine.usage(encrypt, System.out);
 *         } else {
 *             runProgram(encrypt);
 *         }
 *     } catch (ParameterException ex) { // command line arguments could not be parsed
 *         System.err.println(ex.getMessage());
 *         CommandLine.usage(new Encrypt(), System.err);
 *     }
 * }
 * </pre><p>
 * Invoke the above program with some command line arguments. The below are all equivalent:
 * </p>
 * <pre>
 * --verbose --out=outfile in1 in2
 * --verbose --out outfile in1 in2
 * -v --out=outfile in1 in2
 * -v -o outfile in1 in2
 * -v -o=outfile in1 in2
 * -vo outfile in1 in2
 * -vo=outfile in1 in2
 * -v -ooutfile in1 in2
 * -vooutfile in1 in2
 * </pre>
 */
public class CommandLine {
    /** This is picocli version {@value}. */
    public static final String VERSION = "1.0.0-SNAPSHOT";

    private final Tracer tracer = new Tracer();
    private final Interpreter interpreter;
    private boolean overwrittenOptionsAllowed = false;
    private boolean unmatchedArgumentsAllowed = false;
    private List<String> unmatchedArguments = new ArrayList<String>();
    private CommandLine parent;
    private boolean usageHelpRequested;
    private boolean versionHelpRequested;
    private List<String> versionLines = new ArrayList<String>();

    /**
     * Constructs a new {@code CommandLine} interpreter with the specified annotated object.
     * When the {@link #parse(String...)} method is called, fields of the specified object that are annotated
     * with {@code @Option} or {@code @Parameters} will be initialized based on command line arguments.
     * @param command the object to initialize from the command line arguments
     * @throws IllegalArgumentException if the specified command object does not have a {@link Command}, {@link Option} or {@link Parameters} annotation
     */
    public CommandLine(Object command) {
        interpreter = new Interpreter(command);
    }

    /** Registers a subcommand with the specified name. For example:
     * <pre>
     * CommandLine commandLine = new CommandLine(new Git())
     *         .addSubcommand("status",   new GitStatus())
     *         .addSubcommand("commit",   new GitCommit();
     *         .addSubcommand("add",      new GitAdd())
     *         .addSubcommand("branch",   new GitBranch())
     *         .addSubcommand("checkout", new GitCheckout())
     *         //...
     *         ;
     * </pre>
     *
     * <p>The specified object can be an annotated object or a
     * {@code CommandLine} instance with its own nested subcommands. For example:</p>
     * <pre>
     * CommandLine commandLine = new CommandLine(new MainCommand())
     *         .addSubcommand("cmd1",                 new ChildCommand1()) // subcommand
     *         .addSubcommand("cmd2",                 new ChildCommand2())
     *         .addSubcommand("cmd3", new CommandLine(new ChildCommand3()) // subcommand with nested sub-subcommands
     *                 .addSubcommand("cmd3sub1",                 new GrandChild3Command1())
     *                 .addSubcommand("cmd3sub2",                 new GrandChild3Command2())
     *                 .addSubcommand("cmd3sub3", new CommandLine(new GrandChild3Command3()) // deeper nesting
     *                         .addSubcommand("cmd3sub3sub1", new GreatGrandChild3Command3_1())
     *                         .addSubcommand("cmd3sub3sub2", new GreatGrandChild3Command3_2())
     *                 )
     *         );
     * </pre>
     * <p>The default type converters are available on all subcommands and nested sub-subcommands, but custom type
     * converters are registered only with the subcommand hierarchy as it existed when the custom type was registered.
     * To ensure a custom type converter is available to all subcommands, register the type converter last, after
     * adding subcommands.</p>
     * <p>See also the {@link Command#subcommands()} annotation to register subcommands declaratively.</p>
     *
     * @param name the string to recognize on the command line as a subcommand
     * @param command the object to initialize with command line arguments following the subcommand name.
     *          This may be a {@code CommandLine} instance with its own (nested) subcommands
     * @return this CommandLine object, to allow method chaining
     * @see #registerConverter(Class, ITypeConverter)
     * @since 0.9.7
     * @see Command#subcommands()
     */
    public CommandLine addSubcommand(String name, Object command) {
        CommandLine commandLine = toCommandLine(command);
        commandLine.parent = this;
        interpreter.commands.put(name, commandLine);
        return this;
    }
    /** Returns a map with the subcommands {@linkplain #addSubcommand(String, Object) registered} on this instance.
     * @return a map with the registered subcommands
     * @since 0.9.7
     */
    public Map<String, CommandLine> getSubcommands() {
        return new LinkedHashMap<String, CommandLine>(interpreter.commands);
    }
    /**
     * Returns the command that this is a subcommand of, or {@code null} if this is a top-level command.
     * @return the command that this is a subcommand of, or {@code null} if this is a top-level command
     * @see #addSubcommand(String, Object)
     * @see Command#subcommands()
     * @since 0.9.8
     */
    public CommandLine getParent() {
        return parent;
    }

    /**
     * Returns the annotated object that this {@code CommandLine} instance was constructed with.
     * @return the annotated object that this {@code CommandLine} instance was constructed with
     * @since 0.9.7
     */
    public Object getCommand() {
        return interpreter.command;
    }

    /** Returns {@code true} if an option annotated with {@link Option#usageHelp()} was specified on the command line.
     * @return whether the parser encountered an option annotated with {@link Option#usageHelp()}  */
    public boolean isUsageHelpRequested() { return usageHelpRequested; }

    /** Returns {@code true} if an option annotated with {@link Option#versionHelp()} was specified on the command line.
     * @return whether the parser encountered an option annotated with {@link Option#versionHelp()}  */
    public boolean isVersionHelpRequested() { return versionHelpRequested; }

    /** Returns whether options for single-value fields can be specified multiple times on the command line.
     * The default is {@code false} and a {@link OverwrittenOptionException} is thrown if this happens.
     * When {@code true}, the last specified value is retained.
     * @return {@code true} if options for single-value fields can be specified multiple times on the command line, {@code false} otherwise
     * @since 0.9.7
     */
    public boolean isOverwrittenOptionsAllowed() {
        return overwrittenOptionsAllowed;
    }

    /** Sets whether options for single-value fields can be specified multiple times on the command line without a {@link OverwrittenOptionException} being thrown.
     * <p>The specified setting will be registered with this {@code CommandLine} and the full hierarchy of its
     * subcommands and nested sub-subcommands <em>at the moment this method is called</em>. Subcommands added
     * later will have the default setting. To ensure a setting is applied to all
     * subcommands, call the setter last, after adding subcommands.</p>
     * @param newValue the new setting
     * @return this {@code CommandLine} object, to allow method chaining
     * @since 0.9.7
     */
    public CommandLine setOverwrittenOptionsAllowed(boolean newValue) {
        this.overwrittenOptionsAllowed = newValue;
        for (CommandLine command : interpreter.commands.values()) {
            command.setOverwrittenOptionsAllowed(newValue);
        }
        return this;
    }

    /** Returns whether the end user may specify arguments on the command line that are not matched to any option or parameter fields.
     * The default is {@code false} and a {@link UnmatchedArgumentException} is thrown if this happens.
     * When {@code true}, the last unmatched arguments are available via the {@link #getUnmatchedArguments()} method.
     * @return {@code true} if the end use may specify unmatched arguments on the command line, {@code false} otherwise
     * @see #getUnmatchedArguments()
     * @since 0.9.7
     */
    public boolean isUnmatchedArgumentsAllowed() {
        return unmatchedArgumentsAllowed;
    }

    /** Sets whether the end user may specify unmatched arguments on the command line without a {@link UnmatchedArgumentException} being thrown.
     * <p>The specified setting will be registered with this {@code CommandLine} and the full hierarchy of its
     * subcommands and nested sub-subcommands <em>at the moment this method is called</em>. Subcommands added
     * later will have the default setting. To ensure a setting is applied to all
     * subcommands, call the setter last, after adding subcommands.</p>
     * @param newValue the new setting
     * @return this {@code CommandLine} object, to allow method chaining
     * @since 0.9.7
     */
    public CommandLine setUnmatchedArgumentsAllowed(boolean newValue) {
        this.unmatchedArgumentsAllowed = newValue;
        for (CommandLine command : interpreter.commands.values()) {
            command.setUnmatchedArgumentsAllowed(newValue);
        }
        return this;
    }

    /** Returns the list of unmatched command line arguments, if any.
     * @return the list of unmatched command line arguments or an empty list
     * @see #isUnmatchedArgumentsAllowed()
     * @since 0.9.7
     */
    public List<String> getUnmatchedArguments() {
        return unmatchedArguments;
    }

    /**
     * <p>
     * Convenience method that initializes the specified annotated object from the specified command line arguments.
     * </p><p>
     * This is equivalent to
     * </p><pre>
     * CommandLine cli = new CommandLine(command);
     * cli.parse(args);
     * return command;
     * </pre>
     *
     * @param command the object to initialize. This object contains fields annotated with
     *          {@code @Option} or {@code @Parameters}.
     * @param args the command line arguments to parse
     * @param <T> the type of the annotated object
     * @return the specified annotated object
     * @throws IllegalArgumentException if the specified command object does not have a {@link Command}, {@link Option} or {@link Parameters} annotation
     * @throws ParameterException if the specified command line arguments are invalid
     * @since 0.9.7
     */
    public static <T> T populateCommand(T command, String... args) {
        CommandLine cli = toCommandLine(command);
        cli.parse(args);
        return command;
    }

    /**
     * <p>
     * Initializes the annotated object that this {@code CommandLine} was constructed with as well as
     * possibly any registered commands, based on the specified command line arguments,
     * and returns a list of all commands and subcommands that were initialized by this method.
     * </p>
     *
     * @param args the command line arguments to parse
     * @return a list with all commands and subcommands initialized by this method
     * @throws ParameterException if the specified command line arguments are invalid
     */
    public List<CommandLine> parse(String... args) {
        return interpreter.parse(args);
    }

    /**
     * Equivalent to {@code new CommandLine(command).usage(out)}. See {@link #usage(PrintStream)} for details.
     * @param command the object annotated with {@link Command}, {@link Option} and {@link Parameters}
     * @param out the print stream to print the help message to
     * @throws IllegalArgumentException if the specified command object does not have a {@link Command}, {@link Option} or {@link Parameters} annotation
     */
    public static void usage(Object command, PrintStream out) {
        toCommandLine(command).usage(out);
    }

    /**
     * Equivalent to {@code new CommandLine(command).usage(out, ansi)}.
     * See {@link #usage(PrintStream, Help.Ansi)} for details.
     * @param command the object annotated with {@link Command}, {@link Option} and {@link Parameters}
     * @param out the print stream to print the help message to
     * @param ansi whether the usage message should contain ANSI escape codes or not
     * @throws IllegalArgumentException if the specified command object does not have a {@link Command}, {@link Option} or {@link Parameters} annotation
     */
    public static void usage(Object command, PrintStream out, Help.Ansi ansi) {
        toCommandLine(command).usage(out, ansi);
    }

    /**
     * Equivalent to {@code new CommandLine(command).usage(out, colorScheme)}.
     * See {@link #usage(PrintStream, Help.ColorScheme)} for details.
     * @param command the object annotated with {@link Command}, {@link Option} and {@link Parameters}
     * @param out the print stream to print the help message to
     * @param colorScheme the {@code ColorScheme} defining the styles for options, parameters and commands when ANSI is enabled
     * @throws IllegalArgumentException if the specified command object does not have a {@link Command}, {@link Option} or {@link Parameters} annotation
     */
    public static void usage(Object command, PrintStream out, Help.ColorScheme colorScheme) {
        toCommandLine(command).usage(out, colorScheme);
    }

    /**
     * Delegates to {@link #usage(PrintStream, Help.Ansi)} with the {@linkplain Help.Ansi#AUTO platform default}.
     * @param out the printStream to print to
     * @see #usage(PrintStream, Help.ColorScheme)
     */
    public void usage(PrintStream out) {
        usage(out, Help.Ansi.AUTO);
    }

    /**
     * Delegates to {@link #usage(PrintStream, Help.ColorScheme)} with the {@linkplain Help#defaultColorScheme(CommandLine.Help.Ansi) default color scheme}.
     * @param out the printStream to print to
     * @param ansi whether the usage message should include ANSI escape codes or not
     * @see #usage(PrintStream, Help.ColorScheme)
     */
    public void usage(PrintStream out, Help.Ansi ansi) {
        usage(out, Help.defaultColorScheme(ansi));
    }
    /**
     * Prints a usage help message for the annotated command class to the specified {@code PrintStream}.
     * Delegates construction of the usage help message to the {@link Help} inner class and is equivalent to:
     * <pre>
     * Help help = new Help(command).addAllSubcommands(getSubcommands());
     * StringBuilder sb = new StringBuilder()
     *         .append(help.headerHeading())
     *         .append(help.header())
     *         .append(help.synopsisHeading())      //e.g. Usage:
     *         .append(help.synopsis())             //e.g. &lt;main class&gt; [OPTIONS] &lt;command&gt; [COMMAND-OPTIONS] [ARGUMENTS]
     *         .append(help.descriptionHeading())   //e.g. %nDescription:%n%n
     *         .append(help.description())          //e.g. {"Converts foos to bars.", "Use options to control conversion mode."}
     *         .append(help.parameterListHeading()) //e.g. %nPositional parameters:%n%n
     *         .append(help.parameterList())        //e.g. [FILE...] the files to convert
     *         .append(help.optionListHeading())    //e.g. %nOptions:%n%n
     *         .append(help.optionList())           //e.g. -h, --help   displays this help and exits
     *         .append(help.commandListHeading())   //e.g. %nCommands:%n%n
     *         .append(help.commandList())          //e.g.    add       adds the frup to the frooble
     *         .append(help.footerHeading())
     *         .append(help.footer());
     * out.print(sb);
     * </pre>
     * <p>Annotate your class with {@link Command} to control many aspects of the usage help message, including
     * the program name, text of section headings and section contents, and some aspects of the auto-generated sections
     * of the usage help message.
     * <p>To customize the auto-generated sections of the usage help message, like how option details are displayed,
     * instantiate a {@link Help} object and use a {@link Help.TextTable} with more of fewer columns, a custom
     * {@linkplain Help.Layout layout}, and/or a custom option {@linkplain Help.IOptionRenderer renderer}
     * for ultimate control over which aspects of an Option or Field are displayed where.</p>
     * @param out the {@code PrintStream} to print the usage help message to
     * @param colorScheme the {@code ColorScheme} defining the styles for options, parameters and commands when ANSI is enabled
     */
    public void usage(PrintStream out, Help.ColorScheme colorScheme) {
        Help help = new Help(interpreter.command, colorScheme).addAllSubcommands(getSubcommands());
        StringBuilder sb = new StringBuilder()
                .append(help.headerHeading())
                .append(help.header())
                .append(help.synopsisHeading())      //e.g. Usage:
                .append(help.synopsis(help.synopsisHeadingLength())) //e.g. &lt;main class&gt; [OPTIONS] &lt;command&gt; [COMMAND-OPTIONS] [ARGUMENTS]
                .append(help.descriptionHeading())   //e.g. %nDescription:%n%n
                .append(help.description())          //e.g. {"Converts foos to bars.", "Use options to control conversion mode."}
                .append(help.parameterListHeading()) //e.g. %nPositional parameters:%n%n
                .append(help.parameterList())        //e.g. [FILE...] the files to convert
                .append(help.optionListHeading())    //e.g. %nOptions:%n%n
                .append(help.optionList())           //e.g. -h, --help   displays this help and exits
                .append(help.commandListHeading())   //e.g. %nCommands:%n%n
                .append(help.commandList())          //e.g.    add       adds the frup to the frooble
                .append(help.footerHeading())
                .append(help.footer());
        out.print(sb);
    }

    /**
     * Delegates to {@link #printVersionHelp(PrintStream, Help.Ansi)} with the {@linkplain Help.Ansi#AUTO platform default}.
     * @param out the printStream to print to
     * @see #printVersionHelp(PrintStream, Help.Ansi)
     * @since 0.9.8
     */
    public void printVersionHelp(PrintStream out) { printVersionHelp(out, Help.Ansi.AUTO); }

    /**
     * Prints version information from the {@link Command#version()} annotation to the specified {@code PrintStream}.
     * Each element of the array of version strings is printed on a separate line. Version strings may contain
     * <a href="http://picocli.info/#_usage_help_with_styles_and_colors">markup for colors and style</a>.
     * @param out the printStream to print to
     * @param ansi whether the usage message should include ANSI escape codes or not
     * @see Command#version()
     * @see Option#versionHelp()
     * @see #isVersionHelpRequested()
     * @since 0.9.8
     */
    public void printVersionHelp(PrintStream out, Help.Ansi ansi) {
        for (String versionInfo : versionLines) {
            out.println(ansi.new Text(versionInfo));
        }
    }
    /**
     * Prints version information from the {@link Command#version()} annotation to the specified {@code PrintStream}.
     * Each element of the array of version strings is {@linkplain String#format(String, Object...) formatted} with the
     * specified parameters, and printed on a separate line. Both version strings and parameters may contain
     * <a href="http://picocli.info/#_usage_help_with_styles_and_colors">markup for colors and style</a>.
     * @param out the printStream to print to
     * @param ansi whether the usage message should include ANSI escape codes or not
     * @param params Arguments referenced by the format specifiers in the version strings
     * @see Command#version()
     * @see Option#versionHelp()
     * @see #isVersionHelpRequested()
     * @since 1.0.0
     */
    public void printVersionHelp(PrintStream out, Help.Ansi ansi, Object... params) {
        for (String versionInfo : versionLines) {
            out.println(ansi.new Text(String.format(versionInfo, params)));
        }
    }

    /**
     * Delegates to {@link #call(Callable, PrintStream, Help.Ansi, String...)} with {@link Help.Ansi#AUTO}.
     * @param callable the command to call when {@linkplain #populateCommand(Object, String...) parsing} succeeds.
     * @param out the printStream to print to
     * @param args the command line arguments to parse
     * @param <C> the annotated object must implement Runnable
     * @param <T> the return type of the Callable
     * @see #call(Callable, PrintStream, Help.Ansi, String...)
     * @throws IllegalArgumentException if the specified command object does not have a {@link Command}, {@link Option} or {@link Parameters} annotation
     * @throws Exception if the Callable throws an exception
     * @return {@code null} if an error occurred while parsing the command line options, otherwise returns the result of calling the Callable
     */
    public static <C extends Callable<T>, T> T call(C callable, PrintStream out, String... args) throws Exception {
        return call(callable, out, Help.Ansi.AUTO, args);
    }
    /**
     * Convenience method to allow command line application authors to avoid some boilerplate code in their application.
     * The annotated object needs to implement {@link Callable}. Calling this method is equivalent to:
     * <pre>
     * CommandLine cmd = new CommandLine(callable);
     * try {
     *     cmd.parse(args);
     * } catch (Exception ex) {
     *     out.println(ex.getMessage());
     *     cmd.usage(out, ansi);
     *     return null;
     * }
     * return callable.call();
     * </pre>
     * Note that this method is not suitable for commands with subcommands.
     * @param callable the command to call when {@linkplain #populateCommand(Object, String...) parsing} succeeds.
     * @param out the printStream to print to
     * @param ansi whether the usage message should include ANSI escape codes or not
     * @param args the command line arguments to parse
     * @param <C> the annotated object must implement Callable
     * @param <T> the return type of the Callable
     * @throws IllegalArgumentException if the specified command object does not have a {@link Command}, {@link Option} or {@link Parameters} annotation
     * @throws Exception if the Callable throws an exception
     * @return {@code null} if an error occurred while parsing the command line options, otherwise returns the result of calling the Callable
     */
    public static <C extends Callable<T>, T> T call(C callable, PrintStream out, Help.Ansi ansi, String... args) throws Exception {
        CommandLine cmd = new CommandLine(callable); // validate command outside of try-catch
        try {
            cmd.parse(args);
        } catch (Exception ex) {
            out.println(ex.getMessage());
            cmd.usage(out, ansi);
            return null;
        }
        return callable.call();
    }

    /**
     * Delegates to {@link #run(Runnable, PrintStream, Help.Ansi, String...)} with {@link Help.Ansi#AUTO}.
     * @param runnable the command to run when {@linkplain #populateCommand(Object, String...) parsing} succeeds.
     * @param out the printStream to print to
     * @param args the command line arguments to parse
     * @param <R> the annotated object must implement Runnable
     * @see #run(Runnable, PrintStream, Help.Ansi, String...)
     * @throws IllegalArgumentException if the specified command object does not have a {@link Command}, {@link Option} or {@link Parameters} annotation
     */
    public static <R extends Runnable> void run(R runnable, PrintStream out, String... args) {
        run(runnable, out, Help.Ansi.AUTO, args);
    }
    /**
     * Convenience method to allow command line application authors to avoid some boilerplate code in their application.
     * The annotated object needs to implement {@link Runnable}. Calling this method is equivalent to:
     * <pre>
     * CommandLine cmd = new CommandLine(runnable);
     * try {
     *     cmd.parse(args);
     * } catch (Exception ex) {
     *     out.println(ex.getMessage());
     *     cmd.usage(out, ansi);
     *     return;
     * }
     * runnable.run();
     * </pre>
     * Note that this method is not suitable for commands with subcommands.
     * @param runnable the command to run when {@linkplain #populateCommand(Object, String...) parsing} succeeds.
     * @param out the printStream to print to
     * @param ansi whether the usage message should include ANSI escape codes or not
     * @param args the command line arguments to parse
     * @param <R> the annotated object must implement Runnable
     * @throws IllegalArgumentException if the specified command object does not have a {@link Command}, {@link Option} or {@link Parameters} annotation
     */
    public static <R extends Runnable> void run(R runnable, PrintStream out, Help.Ansi ansi, String... args) {
        CommandLine cmd = new CommandLine(runnable); // validate command outside of try-catch
        try {
            cmd.parse(args);
        } catch (Exception ex) {
            out.println(ex.getMessage());
            cmd.usage(out, ansi);
            return;
        }
        runnable.run();
    }

    /**
     * Registers the specified type converter for the specified class. When initializing fields annotated with
     * {@link Option}, the field's type is used as a lookup key to find the associated type converter, and this
     * type converter converts the original command line argument string value to the correct type.
     * <p>
     * Java 8 lambdas make it easy to register custom type converters:
     * </p>
     * <pre>
     * commandLine.registerConverter(java.nio.file.Path.class, s -&gt; java.nio.file.Paths.get(s));
     * commandLine.registerConverter(java.time.Duration.class, s -&gt; java.time.Duration.parse(s));</pre>
     * <p>
     * Built-in type converters are pre-registered for the following java 1.5 types:
     * </p>
     * <ul>
     *   <li>all primitive types</li>
     *   <li>all primitive wrapper types: Boolean, Byte, Character, Double, Float, Integer, Long, Short</li>
     *   <li>any enum</li>
     *   <li>java.io.File</li>
     *   <li>java.math.BigDecimal</li>
     *   <li>java.math.BigInteger</li>
     *   <li>java.net.InetAddress</li>
     *   <li>java.net.URI</li>
     *   <li>java.net.URL</li>
     *   <li>java.nio.charset.Charset</li>
     *   <li>java.sql.Time</li>
     *   <li>java.util.Date</li>
     *   <li>java.util.UUID</li>
     *   <li>java.util.regex.Pattern</li>
     *   <li>StringBuilder</li>
     *   <li>CharSequence</li>
     *   <li>String</li>
     * </ul>
     * <p>The specified converter will be registered with this {@code CommandLine} and the full hierarchy of its
     * subcommands and nested sub-subcommands <em>at the moment the converter is registered</em>. Subcommands added
     * later will not have this converter added automatically. To ensure a custom type converter is available to all
     * subcommands, register the type converter last, after adding subcommands.</p>
     *
     * @param cls the target class to convert parameter string values to
     * @param converter the class capable of converting string values to the specified target type
     * @param <K> the target type
     * @return this CommandLine object, to allow method chaining
     * @see #addSubcommand(String, Object)
     */
    public <K> CommandLine registerConverter(Class<K> cls, ITypeConverter<K> converter) {
        interpreter.converterRegistry.put(Assert.notNull(cls, "class"), Assert.notNull(converter, "converter"));
        for (CommandLine command : interpreter.commands.values()) {
            command.registerConverter(cls, converter);
        }
        return this;
    }

    /** Returns the String that separates option names from option values when parsing command line options. {@code '='} by default.
     * @return the String the parser uses to separate option names from option values */
    public String getSeparator() {
        return interpreter.separator;
    }

    /** Sets the String the parser uses to separate option names from option values to the specified value.
     * @param separator the String that separates option names from option values
     * @return this {@code CommandLine} object, to allow method chaining */
    public CommandLine setSeparator(String separator) {
        interpreter.separator = Assert.notNull(separator, "separator");
        return this;
    }
    private static boolean empty(String str) { return str == null || str.trim().length() == 0; }
    private static boolean empty(Object[] array) { return array == null || array.length == 0; }
    private static boolean empty(Text txt) { return txt == null || txt.plain.toString().trim().length() == 0; }
    private static String str(String[] arr, int i) { return (arr == null || arr.length == 0) ? "" : arr[i]; }
    private static boolean isBoolean(Class<?> type) { return type == Boolean.class || type == Boolean.TYPE; }
    private static CommandLine toCommandLine(Object obj) { return obj instanceof CommandLine ? (CommandLine) obj : new CommandLine(obj);}
    /**
     * <p>
     * Annotate fields in your class with {@code @Option} and picocli will initialize these fields when matching
     * arguments are specified on the command line.
     * </p><p>
     * For example:
     * </p>
     * <pre>import static picocli.CommandLine.*;
     *
     * public class MyClass {
     *     &#064;Parameters(type = File.class, description = "Any number of input files")
     *     private List&lt;File&gt; files = new ArrayList&lt;File&gt;();
     *
     *     &#064;Option(names = { "-o", "--out" }, description = "Output file (default: print to console)")
     *     private File outputFile;
     *
     *     &#064;Option(names = { "-v", "--verbose"}, description = "Verbosely list files processed")
     *     private boolean verbose;
     *
     *     &#064;Option(names = { "-h", "--help", "-?", "-help"}, help = true, description = "Display this help and exit")
     *     private boolean help;
     *
     *     &#064;Option(names = { "-V", "--version"}, help = true, description = "Display version information and exit")
     *     private boolean version;
     * }
     * </pre>
     * <p>
     * A field cannot be annotated with both {@code @Parameters} and {@code @Option} or a
     * {@code ParameterException} is thrown.
     * </p>
     */
    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.FIELD)
    public @interface Option {
        /**
         * One or more option names. At least one option name is required.
         * <p>
         * Different environments have different conventions for naming options, but usually options have a prefix
         * that sets them apart from parameters.
         * Picocli supports all of the below styles. The default separator is {@code '='}, but this can be configured.
         * </p><p>
         * <b>*nix</b>
         * </p><p>
         * In Unix and Linux, options have a short (single-character) name, a long name or both.
         * Short options
         * (<a href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap12.html#tag_12_02">POSIX
         * style</a> are single-character and are preceded by the {@code '-'} character, e.g., {@code `-v'}.
         * <a href="https://www.gnu.org/software/tar/manual/html_node/Long-Options.html">GNU-style</a> long
         * (or <em>mnemonic</em>) options start with two dashes in a row, e.g., {@code `--file'}.
         * </p><p>Picocli supports the POSIX convention that short options can be grouped, with the last option
         * optionally taking a parameter, which may be attached to the option name or separated by a space or
         * a {@code '='} character. The below examples are all equivalent:
         * </p><pre>
         * -xvfFILE
         * -xvf FILE
         * -xvf=FILE
         * -xv --file FILE
         * -xv --file=FILE
         * -x -v --file FILE
         * -x -v --file=FILE
         * </pre><p>
         * <b>DOS</b>
         * </p><p>
         * DOS options mostly have upper case single-character names and start with a single slash {@code '/'} character.
         * Option parameters are separated by a {@code ':'} character. Options cannot be grouped together but
         * must be specified separately. For example:
         * </p><pre>
         * DIR /S /A:D /T:C
         * </pre><p>
         * <b>PowerShell</b>
         * </p><p>
         * Windows PowerShell options generally are a word preceded by a single {@code '-'} character, e.g., {@code `-Help'}.
         * Option parameters are separated by a space or by a {@code ':'} character.
         * </p>
         * @return one or more option names
         */
        String[] names();

        /**
         * Indicates whether this option is required. By default this is false.
         * If an option is required, but a user invokes the program without specifying the required option,
         * a {@link MissingParameterException} is thrown from the {@link #parse(String...)} method.
         * @return whether this option is required
         */
        boolean required() default false;

        /**
         * Set {@code help=true} if this option should disable validation of the remaining arguments:
         * If the {@code help} option is specified, no error message is generated for missing required options.
         * <p>
         * This attribute is useful for special options like help ({@code -h} and {@code --help} on unix,
         * {@code -?} and {@code -Help} on Windows) or version ({@code -V} and {@code --version} on unix,
         * {@code -Version} on Windows).
         * </p>
         * <p>
         * Note that the {@link #parse(String...)} method will not print help documentation. It will only set
         * the value of the annotated field. It is the responsibility of the caller to inspect the annotated fields
         * and take the appropriate action.
         * </p>
         * @return whether this option disables validation of the other arguments
         */
        boolean help() default false;

        /**
         * Set {@code usageHelp=true} if this option allows the user to request usage help. If this option is
         * specified on the command line, picocli will not validate the remaining arguments (so no "missing required
         * option" errors) and the {@link CommandLine#isUsageHelpRequested()} method will return {@code true}.
         * <p>
         * This attribute is useful for special options like help ({@code -h} and {@code --help} on unix,
         * {@code -?} and {@code -Help} on Windows).
         * </p>
         * <p>
         * Note that the {@link #parse(String...)} method will not print usage help documentation. It will only set
         * the value of the annotated field. It is the responsibility of the caller to inspect the annotated fields
         * and take the appropriate action.
         * </p>
         * @return whether this option allows the user to request usage help
         * @since 0.9.8
         */
        boolean usageHelp() default false;

        /**
         * Set {@code versionHelp=true} if this option allows the user to request version information. If this option is
         * specified on the command line, picocli will not validate the remaining arguments (so no "missing required
         * option" errors) and the {@link CommandLine#isVersionHelpRequested()} method will return {@code true}.
         * <p>
         * This attribute is useful for special options like version ({@code -V} and {@code --version} on unix,
         * {@code -Version} on Windows).
         * </p>
         * <p>
         * Note that the {@link #parse(String...)} method will not print version information. It will only set
         * the value of the annotated field. It is the responsibility of the caller to inspect the annotated fields
         * and take the appropriate action.
         * </p>
         * @return whether this option allows the user to request version information
         * @since 0.9.8
         */
        boolean versionHelp() default false;

        /**
         * Description of this option, used when generating the usage documentation.
         * @return the description of this option
         */
        String[] description() default {};

        /**
         * Specifies the minimum number of required parameters and the maximum number of accepted parameters.
         * If an option declares a positive arity, and the user specifies an insufficient number of parameters on the
         * command line, a {@link MissingParameterException} is thrown by the {@link #parse(String...)} method.
         * <p>
         * In many cases picocli can deduce the number of required parameters from the field's type.
         * By default, flags (boolean options) have arity zero,
         * and single-valued type fields (String, int, Integer, double, Double, File, Date, etc) have arity one.
         * Generally, fields with types that cannot hold multiple values can omit the {@code arity} attribute.
         * </p><p>
         * Fields used to capture options with arity two or higher should have a type that can hold multiple values,
         * like arrays or Collections. See {@link #type()} for strongly-typed Collection fields.
         * </p><p>
         * For example, if an option has 2 required parameters and any number of optional parameters,
         * specify {@code @Option(names = "-example", arity = "2..*")}.
         * </p>
         * <b>A note on boolean options</b>
         * <p>
         * By default picocli does not expect boolean options (also called "flags" or "switches") to have a parameter.
         * You can make a boolean option take a required parameter by annotating your field with {@code arity="1"}.
         * For example: </p>
         * <pre>&#064;Option(names = "-v", arity = "1") boolean verbose;</pre>
         * <p>
         * Because this boolean field is defined with arity 1, the user must specify either {@code <program> -v false}
         * or {@code <program> -v true}
         * on the command line, or a {@link MissingParameterException} is thrown by the {@link #parse(String...)}
         * method.
         * </p><p>
         * To make the boolean parameter possible but optional, define the field with {@code arity = "0..1"}.
         * For example: </p>
         * <pre>&#064;Option(names="-v", arity="0..1") boolean verbose;</pre>
         * <p>This will accept any of the below without throwing an exception:</p>
         * <pre>
         * -v
         * -v true
         * -v false
         * </pre>
         * @return how many arguments this option requires
         */
        String arity() default "";

        /**
         * Specify a {@code paramLabel} for the option parameter to be used in the usage help message. If omitted,
         * picocli uses the field name in fish brackets ({@code '<'} and {@code '>'}) by default. Example:
         * <pre>class Example {
         *     &#064;Option(names = {"-o", "--output"}, paramLabel="FILE", description="path of the output file")
         *     private File out;
         *     &#064;Option(names = {"-j", "--jobs"}, arity="0..1", description="Allow N jobs at once; infinite jobs with no arg.")
         *     private int maxJobs = -1;
         * }</pre>
         * <p>By default, the above gives a usage help message like the following:</p><pre>
         * Usage: &lt;main class&gt; [OPTIONS]
         * -o, --output FILE       path of the output file
         * -j, --jobs [&lt;maxJobs&gt;]  Allow N jobs at once; infinite jobs with no arg.
         * </pre>
         * @return name of the option parameter used in the usage help message
         */
        String paramLabel() default "";

        /**
         * <p>
         * Specify a {@code type} if the annotated field is a {@code Collection} that should hold objects other than
         * Strings, or an array of types (one for the key type, one for the value type) if the annotated field is a {@code Map}.
         * </p><p>
         * If the field's type is a {@code Collection}, the generic type parameter of the collection is erased and
         * cannot be determined at runtime. Specify a {@code type} attribute to store values other than String in
         * the Collection. Picocli will use the {@link ITypeConverter}
         * that is {@linkplain #registerConverter(Class, ITypeConverter) registered} for that type to convert
         * the raw String values before they are added to the collection.
         * </p><p>
         * When the field's type is an array, the {@code type} attribute is ignored: the values will be converted
         * to the array component type and the array will be replaced with a new instance containing both the old and
         * the new values. </p>
         * @return the type(s) to convert the raw String values to before adding them to the Collection or Map
         */
        Class<?>[] type() default {String.class};

        /**
         * Specify a regular expression to use to split option parameter values before applying them to the field.
         * All elements resulting from the split are added to the array or Collection. Ignored for single-value fields.
         * @return a regular expression to split option parameter values or {@code ""} if the value should not be split
         * @see String#split(String)
         */
        String split() default "";

        /**
         * Set {@code hidden=true} if this option should not be included in the usage documentation.
         * @return whether this option should be excluded from the usage message
         */
        boolean hidden() default false;
    }
    /**
     * <p>
     * Fields annotated with {@code @Parameters} will be initialized with positional parameters. By specifying the
     * {@link #index()} attribute you can pick which (or what range) of the positional parameters to apply. If no index
     * is specified, the field will get all positional parameters (so it should be an array or a collection).
     * </p><p>
     * When parsing the command line arguments, picocli first tries to match arguments to {@link Option Options}.
     * Positional parameters are the arguments that follow the options, or the arguments that follow a "--" (double
     * dash) argument on the command line.
     * </p><p>
     * For example:
     * </p>
     * <pre>import static picocli.CommandLine.*;
     *
     * public class MyCalcParameters {
     *     &#064;Parameters(type = BigDecimal.class, description = "Any number of input numbers")
     *     private List&lt;BigDecimal&gt; files = new ArrayList&lt;BigDecimal&gt;();
     *
     *     &#064;Option(names = { "-h", "--help", "-?", "-help"}, help = true, description = "Display this help and exit")
     *     private boolean help;
     * }
     * </pre><p>
     * A field cannot be annotated with both {@code @Parameters} and {@code @Option} or a {@code ParameterException}
     * is thrown.</p>
     */
    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.FIELD)
    public @interface Parameters {
        /** Specify an index ("0", or "1", etc.) to pick which of the command line arguments should be assigned to this
         * field. For array or Collection fields, you can also specify an index range ("0..3", or "2..*", etc.) to assign
         * a subset of the command line arguments to this field. The default is "*", meaning all command line arguments.
         * @return an index or range specifying which of the command line arguments should be assigned to this field
         */
        String index() default "*";

        /** Description of the parameter(s), used when generating the usage documentation.
         * @return the description of the parameter(s)
         */
        String[] description() default {};

        /**
         * Specifies the minimum number of required parameters and the maximum number of accepted parameters. If a
         * positive arity is declared, and the user specifies an insufficient number of parameters on the command line,
         * {@link MissingParameterException} is thrown by the {@link #parse(String...)} method.
         * <p>The default depends on the type of the parameter: booleans require no parameters, arrays and Collections
         * accept zero to any number of parameters, and any other type accepts one parameter.</p>
         * @return the range of minimum and maximum parameters accepted by this command
         */
        String arity() default "";

        /**
         * Specify a {@code paramLabel} for the parameter to be used in the usage help message. If omitted,
         * picocli uses the field name in fish brackets ({@code '<'} and {@code '>'}) by default. Example:
         * <pre>class Example {
         *     &#064;Parameters(paramLabel="FILE", description="path of the input FILE(s)")
         *     private File[] inputFiles;
         * }</pre>
         * <p>By default, the above gives a usage help message like the following:</p><pre>
         * Usage: &lt;main class&gt; [FILE...]
         * [FILE...]       path of the input FILE(s)
         * </pre>
         * @return name of the positional parameter used in the usage help message
         */
        String paramLabel() default "";

        /**
         * <p>
         * Specify a {@code type} if the annotated field is a {@code Collection} that should hold objects other than
         * Strings, or an array of types (one for the key type, one for the value type) if the annotated field is a {@code Map}.
         * </p><p>
         * If the field's type is a {@code Collection}, the generic type parameter of the collection is erased and
         * cannot be determined at runtime. Specify a {@code type} attribute to store values other than String in
         * the Collection. Picocli will use the {@link ITypeConverter}
         * that is {@linkplain #registerConverter(Class, ITypeConverter) registered} for that type to convert
         * the raw String values before they are added to the collection.
         * </p><p>
         * When the field's type is an array, the {@code type} attribute is ignored: the values will be converted
         * to the array component type and the array will be replaced with a new instance containing both the old and
         * the new values. </p>
         * @return the type(s) to convert the raw String values to before adding them to the Collection or Map
         */
        Class<?>[] type() default {String.class};

        /**
         * Specify a regular expression to use to split positional parameter values before applying them to the field.
         * All elements resulting from the split are added to the array or Collection. Ignored for single-value fields.
         * @return a regular expression to split operand values or {@code ""} if the value should not be split
         * @see String#split(String)
         */
        String split() default "";

        /**
         * Set {@code hidden=true} if this parameter should not be included in the usage message.
         * @return whether this parameter should be excluded from the usage message
         */
        boolean hidden() default false;
    }

    /**
     * <p>Annotate your class with {@code @Command} when you want more control over the format of the generated help
     * message.
     * </p><pre>
     * &#064;Command(name      = "Encrypt",
     *        description = "Encrypt FILE(s), or standard input, to standard output or to the output file.",
     *        footer      = "Copyright (c) 2017")
     * public class Encrypt {
     *     &#064;Parameters(paramLabel = "FILE", type = File.class, description = "Any number of input files")
     *     private List&lt;File&gt; files     = new ArrayList&lt;File&gt;();
     *
     *     &#064;Option(names = { "-o", "--out" }, description = "Output file (default: print to console)")
     *     private File outputFile;
     * }</pre>
     * <p>
     * The structure of a help message looks like this:
     * </p><ul>
     *   <li>[header]</li>
     *   <li>[synopsis]: {@code Usage: <commandName> [OPTIONS] [FILE...]}</li>
     *   <li>[description]</li>
     *   <li>[parameter list]: {@code      [FILE...]   Any number of input files}</li>
     *   <li>[option list]: {@code   -h, --help   prints this help message and exits}</li>
     *   <li>[footer]</li>
     * </ul> */
    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.TYPE)
    public @interface Command {
        /** Program name to show in the synopsis. If omitted, {@code "<main class>"} is used.
         * For {@linkplain #subcommands() declaratively added} subcommands, this attribute is also used
         * by the parser to recognize subcommands in the command line arguments.
         * @return the program name to show in the synopsis
         * @see Help#commandName */
        String name() default "<main class>";

        /** A list of classes to instantiate and register as subcommands. When registering subcommands declaratively
         * like this, you don't need to call the {@link CommandLine#addSubcommand(String, Object)} method. For example, this:
         * <pre>
         * &#064;Command(subcommands = {
         *         GitStatus.class,
         *         GitCommit.class,
         *         GitBranch.class })
         * public class Git { ... }
         *
         * CommandLine commandLine = new CommandLine(new Git());
         * </pre> is equivalent to this:
         * <pre>
         * // alternative: programmatically add subcommands.
         * // NOTE: in this case there should be no `subcommands` attribute on the @Command annotation.
         * &#064;Command public class Git { ... }
         *
         * CommandLine commandLine = new CommandLine(new Git())
         *         .addSubcommand("status",   new GitStatus())
         *         .addSubcommand("commit",   new GitCommit())
         *         .addSubcommand("branch",   new GitBranch());
         * </pre>
         * @return the declaratively registered subcommands of this command, or an empty array if none
         * @see CommandLine#addSubcommand(String, Object)
         * @since 0.9.8
         */
        Class<?>[] subcommands() default {};

        /** String that separates options from option parameters. Default is {@code "="}. Spaces are also accepted.
         * @return the string that separates options from option parameters, used both when parsing and when generating usage help
         * @see Help#separator
         * @see CommandLine#setSeparator(String) */
        String separator() default "=";

        /** Version information for this command, to print to the console when the user specifies an
         * {@linkplain Option#versionHelp() option} to request version help. This is not part of the usage help message.
         *
         * @return a string or an array of strings with version information about this command.
         * @since 0.9.8
         * @see CommandLine#printVersionHelp(PrintStream)
         */
        String[] version() default {};

        /** Set the heading preceding the header section. May contain embedded {@linkplain java.util.Formatter format specifiers}.
         * @return the heading preceding the header section
         * @see Help#headerHeading(Object...)  */
        String headerHeading() default "";

        /** Optional summary description of the command, shown before the synopsis.
         * @return summary description of the command
         * @see Help#header
         * @see Help#header(Object...)  */
        String[] header() default {};

        /** Set the heading preceding the synopsis text. May contain embedded
         * {@linkplain java.util.Formatter format specifiers}. The default heading is {@code "Usage: "} (without a line
         * break between the heading and the synopsis text).
         * @return the heading preceding the synopsis text
         * @see Help#synopsisHeading(Object...)  */
        String synopsisHeading() default "Usage: ";

        /** Specify {@code true} to generate an abbreviated synopsis like {@code "<main> [OPTIONS] [PARAMETERS...]"}.
         * By default, a detailed synopsis with individual option names and parameters is generated.
         * @return whether the synopsis should be abbreviated
         * @see Help#abbreviateSynopsis
         * @see Help#abbreviatedSynopsis()
         * @see Help#detailedSynopsis(Comparator, boolean) */
        boolean abbreviateSynopsis() default false;

        /** Specify one or more custom synopsis lines to display instead of an auto-generated synopsis.
         * @return custom synopsis text to replace the auto-generated synopsis
         * @see Help#customSynopsis
         * @see Help#customSynopsis(Object...) */
        String[] customSynopsis() default {};

        /** Set the heading preceding the description section. May contain embedded {@linkplain java.util.Formatter format specifiers}.
         * @return the heading preceding the description section
         * @see Help#descriptionHeading(Object...)  */
        String descriptionHeading() default "";

        /** Optional text to display between the synopsis line(s) and the list of options.
         * @return description of this command
         * @see Help#description
         * @see Help#description(Object...) */
        String[] description() default {};

        /** Set the heading preceding the parameters list. May contain embedded {@linkplain java.util.Formatter format specifiers}.
         * @return the heading preceding the parameters list
         * @see Help#parameterListHeading(Object...)  */
        String parameterListHeading() default "";

        /** Set the heading preceding the options list. May contain embedded {@linkplain java.util.Formatter format specifiers}.
         * @return the heading preceding the options list
         * @see Help#optionListHeading(Object...)  */
        String optionListHeading() default "";

        /** Specify {@code false} to show Options in declaration order. The default is to sort alphabetically.
         * @return whether options should be shown in alphabetic order.
         * @see Help#sortOptions */
        boolean sortOptions() default true;

        /** Prefix required options with this character in the options list. The default is no marker: the synopsis
         * indicates which options and parameters are required.
         * @return the character to show in the options list to mark required options
         * @see Help#requiredOptionMarker */
        char requiredOptionMarker() default ' ';

        /** Specify {@code true} to show default values in the description column of the options list (except for
         * boolean options). False by default.
         * @return whether the default values for options and parameters should be shown in the description column
         * @see Help#showDefaultValues */
        boolean showDefaultValues() default false;

        /** Set the heading preceding the subcommands list. May contain embedded {@linkplain java.util.Formatter format specifiers}.
         * The default heading is {@code "Commands:%n"} (with a line break at the end).
         * @return the heading preceding the subcommands list
         * @see Help#commandListHeading(Object...)  */
        String commandListHeading() default "Commands:%n";

        /** Set the heading preceding the footer section. May contain embedded {@linkplain java.util.Formatter format specifiers}.
         * @return the heading preceding the footer section
         * @see Help#footerHeading(Object...)  */
        String footerHeading() default "";

        /** Optional text to display after the list of options.
         * @return text to display after the list of options
         * @see Help#footer
         * @see Help#footer(Object...) */
        String[] footer() default {};
    }
    /**
     * <p>
     * When parsing command line arguments and initializing
     * fields annotated with {@link Option @Option} or {@link Parameters @Parameters},
     * String values can be converted to any type for which a {@code ITypeConverter} is registered.
     * </p><p>
     * This interface defines the contract for classes that know how to convert a String into some domain object.
     * Custom converters can be registered with the {@link #registerConverter(Class, ITypeConverter)} method.
     * </p><p>
     * Java 8 lambdas make it easy to register custom type converters:
     * </p>
     * <pre>
     * commandLine.registerConverter(java.nio.file.Path.class, s -&gt; java.nio.file.Paths.get(s));
     * commandLine.registerConverter(java.time.Duration.class, s -&gt; java.time.Duration.parse(s));</pre>
     * <p>
     * Built-in type converters are pre-registered for the following java 1.5 types:
     * </p>
     * <ul>
     *   <li>all primitive types</li>
     *   <li>all primitive wrapper types: Boolean, Byte, Character, Double, Float, Integer, Long, Short</li>
     *   <li>any enum</li>
     *   <li>java.io.File</li>
     *   <li>java.math.BigDecimal</li>
     *   <li>java.math.BigInteger</li>
     *   <li>java.net.InetAddress</li>
     *   <li>java.net.URI</li>
     *   <li>java.net.URL</li>
     *   <li>java.nio.charset.Charset</li>
     *   <li>java.sql.Time</li>
     *   <li>java.util.Date</li>
     *   <li>java.util.UUID</li>
     *   <li>java.util.regex.Pattern</li>
     *   <li>StringBuilder</li>
     *   <li>CharSequence</li>
     *   <li>String</li>
     * </ul>
     * @param <K> the type of the object that is the result of the conversion
     */
    public interface ITypeConverter<K> {
        /**
         * Converts the specified command line argument value to some domain object.
         * @param value the command line argument String value
         * @return the resulting domain object
         * @throws Exception an exception detailing what went wrong during the conversion
         */
        K convert(String value) throws Exception;
    }
    /** Describes the number of parameters required and accepted by an option or a positional parameter.
     * @since 0.9.7
     */
    public static class Range implements Comparable<Range> {
        /** Required number of parameters for an option or positional parameter. */
        public final int min;
        /** Maximum accepted number of parameters for an option or positional parameter. */
        public final int max;
        public final boolean isVariable;
        private final boolean isUnspecified;
        private final String originalValue;

        /** Constructs a new Range object with the specified parameters.
         * @param min minimum number of required parameters
         * @param max maximum number of allowed parameters (or Integer.MAX_VALUE if variable)
         * @param variable {@code true} if any number or parameters is allowed, {@code false} otherwise
         * @param unspecified {@code true} if no arity was specified on the option/parameter (value is based on type)
         * @param originalValue the original value that was specified on the option or parameter
         */
        public Range(int min, int max, boolean variable, boolean unspecified, String originalValue) {
            this.min = min;
            this.max = max;
            this.isVariable = variable;
            this.isUnspecified = unspecified;
            this.originalValue = originalValue;
        }
        /** Returns a new {@code Range} based on the {@link Option#arity()} annotation on the specified field,
         * or the field type's default arity if no arity was specified.
         * @param field the field whose Option annotation to inspect
         * @return a new {@code Range} based on the Option arity annotation on the specified field */
        public static Range optionArity(Field field) {
            return field.isAnnotationPresent(Option.class)
                    ? adjustForType(Range.valueOf(field.getAnnotation(Option.class).arity()), field)
                    : new Range(0, 0, false, true, "0");
        }
        /** Returns a new {@code Range} based on the {@link Parameters#arity()} annotation on the specified field,
         * or the field type's default arity if no arity was specified.
         * @param field the field whose Parameters annotation to inspect
         * @return a new {@code Range} based on the Parameters arity annotation on the specified field */
        public static Range parameterArity(Field field) {
            return field.isAnnotationPresent(Parameters.class)
                    ? adjustForType(Range.valueOf(field.getAnnotation(Parameters.class).arity()), field)
                    : new Range(0, 0, false, true, "0");
        }
        /** Returns a new {@code Range} based on the {@link Parameters#index()} annotation on the specified field.
         * @param field the field whose Parameters annotation to inspect
         * @return a new {@code Range} based on the Parameters index annotation on the specified field */
        public static Range parameterIndex(Field field) {
            return field.isAnnotationPresent(Parameters.class)
                    ? Range.valueOf(field.getAnnotation(Parameters.class).index())
                    : new Range(0, 0, false, true, "0");
        }
        static Range adjustForType(Range result, Field field) {
            return result.isUnspecified ? defaultArity(field.getType()) : result;
        }
        /** Returns a new {@code Range} based on the specified type: booleans have arity 0, arrays or Collections have
         * arity "0..*", and other types have arity 1.
         * @param type the type whose default arity to return
         * @return a new {@code Range} indicating the default arity of the specified type */
        public static Range defaultArity(Class<?> type) {
            if (isBoolean(type)) {
                return Range.valueOf("0");
            } else if (type.isArray() || Collection.class.isAssignableFrom(type) || Map.class.isAssignableFrom(type)) {
                return Range.valueOf("0..*");
            }
            return Range.valueOf("1");// for single-valued fields
        }
        /** Leniently parses the specified String as an {@code Range} value and return the result. A range string can
         * be a fixed integer value or a range of the form {@code MIN_VALUE + ".." + MAX_VALUE}. If the
         * {@code MIN_VALUE} string is not numeric, the minimum is zero. If the {@code MAX_VALUE} is not numeric, the
         * range is taken to be variable and the maximum is {@code Integer.MAX_VALUE}.
         * @param range the value range string to parse
         * @return a new {@code Range} value */
        public static Range valueOf(String range) {
            range = range.trim();
            boolean unspecified = range.length() == 0 || range.startsWith(".."); // || range.endsWith("..");
            int min = -1, max = -1;
            boolean variable = false;
            int dots = -1;
            if ((dots = range.indexOf("..")) >= 0) {
                min = parseInt(range.substring(0, dots), 0);
                max = parseInt(range.substring(dots + 2), Integer.MAX_VALUE);
                variable = max == Integer.MAX_VALUE;
            } else {
                max = parseInt(range, Integer.MAX_VALUE);
                variable = max == Integer.MAX_VALUE;
                min = variable ? 0 : max;
            }
            Range result = new Range(min, max, variable, unspecified, range);
            return result;
        }
        private static int parseInt(String str, int defaultValue) {
            try {
                return Integer.parseInt(str);
            } catch (Exception ex) {
                return defaultValue;
            }
        }
        /** Returns a new Range object with the {@code min} value replaced by the specified value.
         * The {@code max} of the returned Range is guaranteed not to be less than the new {@code min} value.
         * @param newMin the {@code min} value of the returned Range object
         * @return a new Range object with the specified {@code min} value */
        public Range min(int newMin) { return new Range(newMin, Math.max(newMin, max), isVariable, isUnspecified, originalValue); }

        /** Returns a new Range object with the {@code max} value replaced by the specified value.
         * The {@code min} of the returned Range is guaranteed not to be greater than the new {@code max} value.
         * @param newMax the {@code max} value of the returned Range object
         * @return a new Range object with the specified {@code max} value */
        public Range max(int newMax) { return new Range(Math.min(min, newMax), newMax, isVariable, isUnspecified, originalValue); }

        public boolean equals(Object object) {
            if (!(object instanceof Range)) { return false; }
            Range other = (Range) object;
            return other.max == this.max && other.min == this.min && other.isVariable == this.isVariable;
        }
        public int hashCode() {
            return ((17 * 37 + max) * 37 + min) * 37 + (isVariable ? 1 : 0);
        }
        public String toString() {
            return min == max ? String.valueOf(min) : min + ".." + (isVariable ? "*" : max);
        }
        public int compareTo(Range other) {
            int result = min - other.min;
            return (result == 0) ? max - other.max : result;
        }
    }
    static void init(Class<?> cls,
                              List<Field> requiredFields,
                              Map<String, Field> optionName2Field,
                              Map<Character, Field> singleCharOption2Field,
                              List<Field> positionalParametersFields) {
        Field[] declaredFields = cls.getDeclaredFields();
        for (Field field : declaredFields) {
            field.setAccessible(true);
            if (field.isAnnotationPresent(Option.class)) {
                Option option = field.getAnnotation(Option.class);
                if (option.required()) {
                    requiredFields.add(field);
                }
                for (String name : option.names()) { // cannot be null or empty
                    Field existing = optionName2Field.put(name, field);
                    if (existing != null && existing != field) {
                        throw DuplicateOptionAnnotationsException.create(name, field, existing);
                    }
                    if (name.length() == 2 && name.startsWith("-")) {
                        char flag = name.charAt(1);
                        Field existing2 = singleCharOption2Field.put(flag, field);
                        if (existing2 != null && existing2 != field) {
                            throw DuplicateOptionAnnotationsException.create(name, field, existing2);
                        }
                    }
                }
            }
            if (field.isAnnotationPresent(Parameters.class)) {
                if (field.isAnnotationPresent(Option.class)) {
                    throw new ParameterException("A field can be either @Option or @Parameters, but '"
                            + field.getName() + "' is both.");
                }
                positionalParametersFields.add(field);
                Range arity = Range.parameterArity(field);
                if (arity.min > 0) {
                    requiredFields.add(field);
                }
            }
        }
    }
    static void validatePositionalParameters(List<Field> positionalParametersFields) {
        int min = 0;
        for (Field field : positionalParametersFields) {
            Range index = Range.parameterIndex(field);
            if (index.min > min) {
                throw new ParameterIndexGapException("Missing field annotated with @Parameter(index=" + min +
                        "). Nearest field '" + field.getName() + "' has index=" + index.min);
            }
            min = Math.max(min, index.max);
            min = min == Integer.MAX_VALUE ? min : min + 1;
        }
    }
    private static <T> Stack<T> reverse(Stack<T> stack) {
        Collections.reverse(stack);
        return stack;
    }
    /**
     * Helper class responsible for processing command line arguments.
     */
    private class Interpreter {
        private final Map<String, CommandLine> commands                  = new LinkedHashMap<String, CommandLine>();
        private final Map<Class<?>, ITypeConverter<?>> converterRegistry = new HashMap<Class<?>, ITypeConverter<?>>();
        private final Map<String, Field> optionName2Field                = new HashMap<String, Field>();
        private final Map<Character, Field> singleCharOption2Field       = new HashMap<Character, Field>();
        private final List<Field> requiredFields                         = new ArrayList<Field>();
        private final List<Field> positionalParametersFields             = new ArrayList<Field>();
        private final Object command;
        private boolean isHelpRequested;
        private String separator = "=";

        Interpreter(Object command) {
            converterRegistry.put(String.class,        new BuiltIn.StringConverter());
            converterRegistry.put(StringBuilder.class, new BuiltIn.StringBuilderConverter());
            converterRegistry.put(CharSequence.class,  new BuiltIn.CharSequenceConverter());
            converterRegistry.put(Byte.class,          new BuiltIn.ByteConverter());
            converterRegistry.put(Byte.TYPE,           new BuiltIn.ByteConverter());
            converterRegistry.put(Boolean.class,       new BuiltIn.BooleanConverter());
            converterRegistry.put(Boolean.TYPE,        new BuiltIn.BooleanConverter());
            converterRegistry.put(Character.class,     new BuiltIn.CharacterConverter());
            converterRegistry.put(Character.TYPE,      new BuiltIn.CharacterConverter());
            converterRegistry.put(Short.class,         new BuiltIn.ShortConverter());
            converterRegistry.put(Short.TYPE,          new BuiltIn.ShortConverter());
            converterRegistry.put(Integer.class,       new BuiltIn.IntegerConverter());
            converterRegistry.put(Integer.TYPE,        new BuiltIn.IntegerConverter());
            converterRegistry.put(Long.class,          new BuiltIn.LongConverter());
            converterRegistry.put(Long.TYPE,           new BuiltIn.LongConverter());
            converterRegistry.put(Float.class,         new BuiltIn.FloatConverter());
            converterRegistry.put(Float.TYPE,          new BuiltIn.FloatConverter());
            converterRegistry.put(Double.class,        new BuiltIn.DoubleConverter());
            converterRegistry.put(Double.TYPE,         new BuiltIn.DoubleConverter());
            converterRegistry.put(File.class,          new BuiltIn.FileConverter());
            converterRegistry.put(URI.class,           new BuiltIn.URIConverter());
            converterRegistry.put(URL.class,           new BuiltIn.URLConverter());
            converterRegistry.put(Date.class,          new BuiltIn.ISO8601DateConverter());
            converterRegistry.put(Time.class,          new BuiltIn.ISO8601TimeConverter());
            converterRegistry.put(BigDecimal.class,    new BuiltIn.BigDecimalConverter());
            converterRegistry.put(BigInteger.class,    new BuiltIn.BigIntegerConverter());
            converterRegistry.put(Charset.class,       new BuiltIn.CharsetConverter());
            converterRegistry.put(InetAddress.class,   new BuiltIn.InetAddressConverter());
            converterRegistry.put(Pattern.class,       new BuiltIn.PatternConverter());
            converterRegistry.put(UUID.class,          new BuiltIn.UUIDConverter());

            this.command             = Assert.notNull(command, "command");
            Class<?> cls             = command.getClass();
            String declaredSeparator = null;
            boolean hasCommandAnnotation = false;
            while (cls != null) {
                init(cls, requiredFields, optionName2Field, singleCharOption2Field, positionalParametersFields);
                if (cls.isAnnotationPresent(Command.class)) {
                    hasCommandAnnotation = true;
                    Command cmd = cls.getAnnotation(Command.class);
                    declaredSeparator = (declaredSeparator == null) ? cmd.separator() : declaredSeparator;
                    CommandLine.this.versionLines.addAll(Arrays.asList(cmd.version()));

                    for (Class<?> sub : cmd.subcommands()) {
                        Command subCommand = sub.getAnnotation(Command.class);
                        if (subCommand == null || Help.DEFAULT_COMMAND_NAME.equals(subCommand.name())) {
                            throw new IllegalArgumentException("Subcommand " + sub.getName() +
                                    " is missing the mandatory @Command annotation with a 'name' attribute");
                        }
                        try {
                            Constructor<?> constructor = sub.getDeclaredConstructor();
                            constructor.setAccessible(true);
                            CommandLine commandLine = toCommandLine(constructor.newInstance());
                            commandLine.parent = CommandLine.this;
                            commands.put(subCommand.name(), commandLine);
                        }
                        catch (IllegalArgumentException ex) { throw ex; }
                        catch (NoSuchMethodException ex) { throw new IllegalArgumentException("Cannot instantiate subcommand " +
                                sub.getName() + ": the class has no constructor", ex); }
                        catch (Exception ex) {
                            throw new IllegalStateException("Could not instantiate and add subcommand " +
                                    sub.getName() + ": " + ex, ex);
                        }
                    }
                }
                cls = cls.getSuperclass();
            }
            separator = declaredSeparator != null ? declaredSeparator : separator;
            Collections.sort(positionalParametersFields, new PositionalParametersSorter());
            validatePositionalParameters(positionalParametersFields);

            if (positionalParametersFields.isEmpty() && optionName2Field.isEmpty() && !hasCommandAnnotation) {
                throw new IllegalArgumentException(command + " (" + command.getClass() +
                        ") is not a command: it has no @Command, @Option or @Parameters annotations");
            }
        }

        /**
         * Entry point into parsing command line arguments.
         * @param args the command line arguments
         * @return a list with all commands and subcommands initialized by this method
         * @throws ParameterException if the specified command line arguments are invalid
         */
        List<CommandLine> parse(String... args) {
            Assert.notNull(args, "argument array");
            tracer.info("Parsing %d command line args %s%n", args.length, Arrays.toString(args));
            Stack<String> arguments = new Stack<String>();
            for (int i = args.length - 1; i >= 0; i--) {
                arguments.push(args[i]);
            }
            List<CommandLine> result = new ArrayList<CommandLine>();
            parse(result, arguments, args);
            return result;
        }

        private void parse(List<CommandLine> parsedCommands, Stack<String> argumentStack, String[] originalArgs) {
            // first reset any state in case this CommandLine instance is being reused
            isHelpRequested = false;
            CommandLine.this.versionHelpRequested = false;
            CommandLine.this.usageHelpRequested = false;

            Class<?> cmdClass = this.command.getClass();
            if (tracer.isDebug()) {tracer.debug("Initializing %s: %d options, %d positional parameters, %d required, %d subcommands.%n", cmdClass.getName(), new HashSet<Field>(optionName2Field.values()).size(), positionalParametersFields.size(), requiredFields.size(), commands.size());}
            parsedCommands.add(CommandLine.this);
            List<Field> required = new ArrayList<Field>(requiredFields);
            Set<Field> initialized = new HashSet<Field>();
            Collections.sort(required, new PositionalParametersSorter());
            try {
                processArguments(parsedCommands, argumentStack, required, initialized, originalArgs);
            } catch (ParameterException ex) {
                throw ex;
            } catch (Exception ex) {
                int offendingArgIndex = originalArgs.length - argumentStack.size() - 1;
                String arg = offendingArgIndex >= 0 && offendingArgIndex < originalArgs.length ? originalArgs[offendingArgIndex] : "?";
                throw ParameterException.create(ex, arg, offendingArgIndex, originalArgs);
            }
            if (!isAnyHelpRequested() && !required.isEmpty()) {
                if (required.get(0).isAnnotationPresent(Option.class)) {
                    throw MissingParameterException.create(required);
                } else {
                    try {
                        processPositionalParameters0(required, true, new Stack<String>());
                    } catch (ParameterException ex) { throw ex;
                    } catch (Exception ex) { throw new IllegalStateException("Internal error: " + ex, ex); }
                }
            }
        }

        private void processArguments(List<CommandLine> parsedCommands,
                                      Stack<String> args,
                                      Collection<Field> required,
                                      Set<Field> initialized,
                                      String[] originalArgs) throws Exception {
            // arg must be one of:
            // 1. the "--" double dash separating options from positional arguments
            // 1. a stand-alone flag, like "-v" or "--verbose": no value required, must map to boolean or Boolean field
            // 2. a short option followed by an argument, like "-f file" or "-ffile": may map to any type of field
            // 3. a long option followed by an argument, like "-file out.txt" or "-file=out.txt"
            // 3. one or more remaining arguments without any associated options. Must be the last in the list.
            // 4. a combination of stand-alone options, like "-vxr". Equivalent to "-v -x -r", "-v true -x true -r true"
            // 5. a combination of stand-alone options and one option with an argument, like "-vxrffile"

            while (!args.isEmpty()) {
                String arg = args.pop();
                if (tracer.isDebug()) {tracer.debug("Processing argument '%s'. Remainder=%s%n", arg, reverse((Stack<String>) args.clone()));}

                // Double-dash separates options from positional arguments.
                // If found, then interpret the remaining args as positional parameters.
                if ("--".equals(arg)) {
                    tracer.info("Found end-of-options delimiter '--'. Treating remainder as positional parameters.%n");
                    processPositionalParameters(required, args);
                    return; // we are done
                }

                // if we find another command, we are done with the current command
                if (commands.containsKey(arg)) {
                    if (!isHelpRequested && !required.isEmpty()) { // ensure current command portion is valid
                        throw MissingParameterException.create(required);
                    }
                    if (tracer.isDebug()) {tracer.debug("Found subcommand '%s' (%s)%n", arg, commands.get(arg).interpreter.command.getClass().getName());}
                    commands.get(arg).interpreter.parse(parsedCommands, args, originalArgs);
                    return; // remainder done by the command
                }

                // First try to interpret the argument as a single option (as opposed to a compact group of options).
                // A single option may be without option parameters, like "-v" or "--verbose" (a boolean value),
                // or an option may have one or more option parameters.
                // A parameter may be attached to the option.
                boolean paramAttachedToOption = false;
                int separatorIndex = arg.indexOf(separator);
                if (separatorIndex > 0) {
                    String key = arg.substring(0, separatorIndex);
                    // be greedy. Consume the whole arg as an option if possible.
                    if (optionName2Field.containsKey(key) && !optionName2Field.containsKey(arg)) {
                        paramAttachedToOption = true;
                        String optionParam = arg.substring(separatorIndex + separator.length());
                        args.push(optionParam);
                        arg = key;
                        if (tracer.isDebug()) {tracer.debug("Separated '%s' option from '%s' option parameter%n", key, optionParam);}
                    } else {
                        if (tracer.isDebug()) {tracer.debug("'%s' contains separator '%s' but '%s' is not a known option%n", arg, separator, key);}
                    }
                } else {
                    if (tracer.isDebug()) {tracer.debug("'%s' cannot be separated into <option>%s<option-parameter>%n", arg, separator);}
                }
                if (optionName2Field.containsKey(arg)) {
                    processStandaloneOption(required, initialized, arg, args, paramAttachedToOption);
                }
                // Compact (single-letter) options can be grouped with other options or with an argument.
                // only single-letter options can be combined with other options or with an argument
                else if (arg.length() > 2 && arg.startsWith("-")) {
                    if (tracer.isDebug()) {tracer.debug("Trying to process '%s' as clustered short options%n", arg, args);}
                    processClusteredShortOptions(required, initialized, arg, args);
                }
                // The argument could not be interpreted as an option.
                // We take this to mean that the remainder are positional arguments
                else {
                    args.push(arg);
                    if (tracer.isDebug()) {tracer.debug("No option named '%s' found. Processing remainder as positional parameters%n", arg);}
                    processPositionalParameters(required, args);
                    return;
                }
            }
        }

        private void processPositionalParameters(Collection<Field> required, Stack<String> args) throws Exception {
            processPositionalParameters0(required, false, args);
            if (!args.empty()) {
                handleUnmatchedArguments(args);
                return;
            };
        }

        private void handleUnmatchedArguments(Stack<String> args) {
            if (!isUnmatchedArgumentsAllowed()) { throw new UnmatchedArgumentException(args); }
            while (!args.isEmpty()) { unmatchedArguments.add(args.pop()); } // addAll would give args in reverse order
            tracer.info("Stored remainder in unmatched arguments list: %s%n", unmatchedArguments);
        }

        private void processPositionalParameters0(Collection<Field> required, boolean validateOnly, Stack<String> args) throws Exception {
            if (tracer.isDebug()) {tracer.debug("Processing positional parameters. Remainder=%s%n", reverse((Stack<String>) args.clone()));}
            int max = 0;
            for (Field positionalParam : positionalParametersFields) {
                Range indexRange = Range.parameterIndex(positionalParam);
                @SuppressWarnings("unchecked")
                Stack<String> argsCopy = reverse((Stack<String>) args.clone());
                if (!indexRange.isVariable) {
                    for (int i = argsCopy.size() - 1; i > indexRange.max; i--) {
                        argsCopy.removeElementAt(i);
                    }
                }
                Collections.reverse(argsCopy);
                for (int i = 0; i < indexRange.min && !argsCopy.isEmpty(); i++) { argsCopy.pop(); }
                Range arity = Range.parameterArity(positionalParam);
                if (tracer.isDebug()) {tracer.debug("Trying to assign args at index %s %s to %s, arity=%s%n", indexRange, reverse((Stack<String>) argsCopy.clone()), positionalParam, arity);}
                assertNoMissingParameters(positionalParam, arity.min, argsCopy);
                if (!validateOnly) {
                    int originalSize = argsCopy.size();
                    int count = applyOption(positionalParam, Parameters.class, arity, false, argsCopy, null, "args[" + indexRange + "]");
                    if (count > 0) { required.remove(positionalParam); }
                    max = Math.max(max, indexRange.min + (originalSize - argsCopy.size())); // track unprocessed args
                }
            }
            // remove processed args from the stack
            if (!validateOnly && !positionalParametersFields.isEmpty()) {
                int processedArgCount = Math.min(args.size(), max < Integer.MAX_VALUE ? max : Integer.MAX_VALUE);
                for (int i = 0; i < processedArgCount; i++) { args.pop(); }
            }
        }

        private void processStandaloneOption(Collection<Field> required,
                                             Set<Field> initialized,
                                             String arg,
                                             Stack<String> args,
                                             boolean paramAttachedToKey) throws Exception {
            Field field = optionName2Field.get(arg);
            required.remove(field);
            Range arity = Range.optionArity(field);
            if (paramAttachedToKey) {
                arity = arity.min(Math.max(1, arity.min)); // if key=value, minimum arity is at least 1
            }
            if (tracer.isDebug()) {tracer.debug("Found option named '%s': field %s, arity=%s%n", arg, field, arity);}
            applyOption(field, Option.class, arity, paramAttachedToKey, args, initialized, "option " + arg);
        }

        private void processClusteredShortOptions(Collection<Field> required,
                                                  Set<Field> initialized,
                                                  String arg,
                                                  Stack<String> args)
                throws Exception {
            String prefix = arg.substring(0, 1);
            String cluster = arg.substring(1);
            boolean paramAttachedToOption = true;
            do {
                if (cluster.length() > 0 && singleCharOption2Field.containsKey(cluster.charAt(0))) {
                    Field field = singleCharOption2Field.get(cluster.charAt(0));
                    Range arity = Range.optionArity(field);
                    String argDescription = "option " + prefix + cluster.charAt(0);
                    if (tracer.isDebug()) {tracer.debug("Found option '%s%s' in %s: field %s, arity=%s%n", prefix, cluster.charAt(0), arg, field, arity);}
                    required.remove(field);
                    cluster = cluster.length() > 0 ? cluster.substring(1) : "";
                    paramAttachedToOption = cluster.length() > 0;
                    if (cluster.startsWith(separator)) {// attached with separator, like -f=FILE or -v=true
                        cluster = cluster.substring(separator.length());
                        arity = arity.min(Math.max(1, arity.min)); // if key=value, minimum arity is at least 1
                    }
                    if (arity.min > 0) {
                        if (tracer.isDebug() && !empty(cluster)) {tracer.debug("Trying to process '%s' as option parameter%n", cluster);}
                    }
                    args.push(cluster); // interpret remainder as option parameter (CAUTION: may be empty string!)
                    // arity may be >= 1, or
                    // arity <= 0 && !cluster.startsWith(separator)
                    // e.g., boolean @Option("-v", arity=0, varargs=true); arg "-rvTRUE", remainder cluster="TRUE"
                    int consumed = applyOption(field, Option.class, arity, paramAttachedToOption, args, initialized, argDescription);
                    // only return if cluster (and maybe more) was consumed, otherwise continue do-while loop
                    if (consumed > 0) {
                        return;
                    }
                    cluster = args.pop();
                } else { // cluster is empty || cluster.charAt(0) is not a short option key
                    if (cluster.length() == 0) { // we finished parsing a group of short options like -rxv
                        return; // return normally and parse the next arg
                    }
                    // We get here when the remainder of the cluster group is neither an option,
                    // nor a parameter that the last option could consume.
                    if (arg.endsWith(cluster)) {
                        // remainder was part of a clustered group that could not be completely parsed
                        args.push(paramAttachedToOption ? prefix + cluster : cluster);
                        if (tracer.isDebug()) {tracer.debug("No option found for %s in %s%n", cluster, arg);}
                        handleUnmatchedArguments(args);
                    } else {
                        args.push(cluster);
                        if (tracer.isDebug()) {tracer.debug("%s is not an option parameter for %s%n", cluster, arg);}
                        processPositionalParameters(required, args);
                    }
                    return;
                }
            } while (true);
        }

        private int applyOption(Field field,
                                Class<?> annotation,
                                Range arity,
                                boolean valueAttachedToOption,
                                Stack<String> args,
                                Set<Field> initialized,
                                String argDescription) throws Exception {
            updateHelpRequested(field);
            if (!args.isEmpty() && args.peek().length() == 0 && !valueAttachedToOption) {
                args.pop(); // throw out empty string we get at the end of a group of clustered short options
            }
            int length = args.size();
            assertNoMissingParameters(field, arity.min, args);

            Class<?> cls = field.getType();
            if (cls.isArray()) {
                return applyValuesToArrayField(field, annotation, arity, args, cls, argDescription);
            }
            if (Collection.class.isAssignableFrom(cls)) {
                return applyValuesToCollectionField(field, annotation, arity, args, cls, argDescription);
            }
            if (Map.class.isAssignableFrom(cls)) {
                return applyValuesToMapField(field, annotation, arity, args, cls, argDescription);
            }
            return applyValueToSingleValuedField(field, arity, args, cls, initialized, argDescription);
        }

        private int applyValueToSingleValuedField(Field field,
                                                  Range arity,
                                                  Stack<String> args,
                                                  Class<?> cls,
                                                  Set<Field> initialized,
                                                  String argDescription) throws Exception {
            boolean noMoreValues = args.isEmpty();
            String value = args.isEmpty() ? null : trim(args.pop()); // unquote the value
            int result = arity.min; // the number or args we need to consume

            // special logic for booleans: BooleanConverter accepts only "true" or "false".
            if ((cls == Boolean.class || cls == Boolean.TYPE) && arity.min <= 0) {

                // boolean option with arity = 0..1 or 0..*: value MAY be a param
                if (arity.max > 0 && ("true".equalsIgnoreCase(value) || "false".equalsIgnoreCase(value))) {
                    result = 1;            // if it is a varargs we only consume 1 argument if it is a boolean value
                } else {
                    if (value != null) {
                        args.push(value); // we don't consume the value
                    }
                    Boolean currentValue = (Boolean) field.get(command);
                    value = String.valueOf(currentValue == null ? true : !currentValue); // #147 toggle existing boolean value
                }
            }
            if (noMoreValues && value == null) {
                return 0;
            }
            if (initialized != null) {
                if (initialized.contains(field) && !isOverwrittenOptionsAllowed()) {
                    throw new OverwrittenOptionException(optionDescription("", field, 0) +  " should be specified only once");
                }
                initialized.add(field);
            }
            ITypeConverter<?> converter = getTypeConverter(cls, field);
            Object objValue = tryConvert(field, -1, converter, value, cls);
            field.set(command, objValue);
            tracer.info("Setting %s field '%s.%s' to '%s' for %s%n", field.getType().getSimpleName(), field.getDeclaringClass().getSimpleName(), field.getName(), String.valueOf(objValue), argDescription);
            return result;
        }
        private int applyValuesToMapField(Field field,
                                          Class<?> annotation,
                                          Range arity,
                                          Stack<String> args,
                                          Class<?> cls,
                                          String argDescription) throws Exception {
            Class<?>[] classes = getTypeAttribute(field);
            if (classes.length < 2) { throw new ParameterException("Field " + field + " needs two types (one for the map key, one for the value) but only has " + classes.length + " types configured."); }
            ITypeConverter<?> keyConverter   = getTypeConverter(classes[0], field);
            ITypeConverter<?> valueConverter = getTypeConverter(classes[1], field);
            Map<Object, Object> result = (Map<Object, Object>) field.get(command);
            if (result == null) {
                result = createMap(cls);
                field.set(command, result);
            }
            int originalSize = result.size();
            consumeMapArguments(field, arity, args, classes, keyConverter, valueConverter, result, argDescription);
            return result.size() - originalSize;
        }

        private void consumeMapArguments(Field field,
                                         Range arity,
                                         Stack<String> args,
                                         Class<?>[] classes,
                                         ITypeConverter<?> keyConverter,
                                         ITypeConverter<?> valueConverter,
                                         Map<Object, Object> result,
                                         String argDescription) throws Exception {
            // first do the arity.min mandatory parameters
            for (int i = 0; result.size() < arity.min; i++) {
                consumeOneMapArgument(field, arity, args, classes, keyConverter, valueConverter, result, argDescription);
            }
            // now process the varargs if any
            while (result.size() < arity.max && !args.isEmpty()) {
                if (!field.isAnnotationPresent(Parameters.class)) {
                    if (commands.containsKey(args.peek()) || isOption(args.peek())) {
                        return;
                    }
                }
                consumeOneMapArgument(field, arity, args, classes, keyConverter, valueConverter, result, argDescription);
            }
        }

        private void consumeOneMapArgument(Field field,
                                           Range arity,
                                           Stack<String> args,
                                           Class<?>[] classes,
                                           ITypeConverter<?> keyConverter, ITypeConverter<?> valueConverter,
                                           Map<Object, Object> result,
                                           String argDescription) throws Exception {
            String[] values = split(trim(args.pop()), field);

            // ensure we don't process more than arity.max (as result of splitting args)
            int max = Math.min(arity.max - result.size(), values.length);
            for (int j = 0; j < max; j++) {
                String value = values[j];
                String[] keyValue = value.split("=");
                if (keyValue.length < 2) {
                    String splitRegex = splitRegex(field);
                    if (splitRegex.length() == 0) {
                        throw new ParameterException("Value for option " + optionDescription("", field,
                                0) + " should be in KEY=VALUE format but was " + value);
                    } else {
                        throw new ParameterException("Value for option " + optionDescription("", field,
                                0) + " should be in KEY=VALUE[" + splitRegex + "KEY=VALUE]... format but was " + value);
                    }
                }
                Object mapKey =   tryConvert(field, j, keyConverter,   keyValue[0], classes[0]);
                Object mapValue = tryConvert(field, j, valueConverter, keyValue[1], classes[1]);
                result.put(mapKey, mapValue);
                tracer.info("Putting [%s : %s] in %s<%s, %s> field '%s.%s' for %s%n", String.valueOf(mapKey), String.valueOf(mapValue),
                        result.getClass().getSimpleName(), classes[0].getSimpleName(), classes[1].getSimpleName(), field.getDeclaringClass().getSimpleName(), field.getName(), argDescription);
            }
            checkMaxArityExceeded(arity, max, field, values);
        }

        private void checkMaxArityExceeded(Range arity, int remainder, Field field, String[] values) {
            if (values.length <= remainder) { return; }
            String desc = arity.max == remainder ? "" + remainder : arity + ", remainder=" + remainder;
            throw new MaxValuesforFieldExceededException(optionDescription("", field, -1) +
                    " max number of values (" + arity.max + ") exceeded: remainder is " + remainder + " but " +
                    values.length + " values were specified: " + Arrays.toString(values));
        }

        private int applyValuesToArrayField(Field field,
                                            Class<?> annotation,
                                            Range arity,
                                            Stack<String> args,
                                            Class<?> cls,
                                            String argDescription) throws Exception {
            Object existing = field.get(command);
            int length = existing == null ? 0 : Array.getLength(existing);
            Class<?> type = cls.getComponentType();
            List<Object> converted = consumeArguments(field, annotation, arity, args, type, length, argDescription);
            List<Object> newValues = new ArrayList<Object>();
            for (int i = 0; i < length; i++) {
                newValues.add(Array.get(existing, i));
            }
            for (Object obj : converted) {
                if (obj instanceof Collection<?>) {
                    newValues.addAll((Collection<?>) obj);
                } else {
                    newValues.add(obj);
                }
            }
            Object array = Array.newInstance(type, newValues.size());
            field.set(command, array);
            for (int i = 0; i < newValues.size(); i++) {
                Array.set(array, i, newValues.get(i));
            }
            return converted.size(); // return how many args were consumed
        }

        @SuppressWarnings("unchecked")
        private int applyValuesToCollectionField(Field field,
                                                 Class<?> annotation,
                                                 Range arity,
                                                 Stack<String> args,
                                                 Class<?> cls,
                                                 String argDescription) throws Exception {
            Collection<Object> collection = (Collection<Object>) field.get(command);
            Class<?> type = getTypeAttribute(field)[0];
            int length = collection == null ? 0 : collection.size();
            List<Object> converted = consumeArguments(field, annotation, arity, args, type, length, argDescription);
            if (collection == null) {
                collection = createCollection(cls);
                field.set(command, collection);
            }
            for (Object element : converted) {
                if (element instanceof Collection<?>) {
                    collection.addAll((Collection<?>) element);
                } else {
                    collection.add(element);
                }
            }
            return converted.size();
        }

        private List<Object> consumeArguments(Field field,
                                              Class<?> annotation,
                                              Range arity,
                                              Stack<String> args,
                                              Class<?> type,
                                              int originalSize,
                                              String argDescription) throws Exception {
            List<Object> result = new ArrayList<Object>();
            int index = 0;

            // first do the arity.min mandatory parameters
            for (int i = 0; result.size() + originalSize < arity.min; i++) {
                index = consumeOneArgument(field, arity, args, type, result, index, originalSize, argDescription);
            }
            // now process the varargs if any
            while (result.size() < arity.max && !args.isEmpty()) {
                if (annotation != Parameters.class) {
                    if (commands.containsKey(args.peek()) || isOption(args.peek())) {
                        return result;
                    }
                }
                index = consumeOneArgument(field, arity, args, type, result, index, originalSize, argDescription);
            }
            return result;
        }

        private int consumeOneArgument(Field field,
                                       Range arity,
                                       Stack<String> args,
                                       Class<?> type,
                                       List<Object> result,
                                       int index,
                                       int originalSize,
                                       String argDescription) throws Exception {
            String[] values = split(trim(args.pop()), field);
            ITypeConverter<?> converter = getTypeConverter(type, field);

            // ensure we don't process more than arity.max (as result of splitting args)
            int max = Math.min(arity.max - (result.size() + originalSize), values.length);
            for (int j = 0; j < max; j++) {
                result.add(tryConvert(field, index, converter, values[j], type));
                if (field.getType().isArray()) {
                    tracer.info("Adding [%s] to %s[] field '%s.%s' for %s%n", String.valueOf(result.get(result.size()-1)), type.getSimpleName(), field.getDeclaringClass().getSimpleName(), field.getName(), argDescription);
                } else {
                    tracer.info("Adding [%s] to %s<%s> field '%s.%s' for %s%n", String.valueOf(result.get(result.size()-1)), field.getType().getSimpleName(), type.getSimpleName(), field.getDeclaringClass().getSimpleName(), field.getName(), argDescription);
                }
            }
            checkMaxArityExceeded(arity, max, field, values);
            index++;
            return index;
        }

        private String splitRegex(Field field) {
            if (field.isAnnotationPresent(Option.class))     { return field.getAnnotation(Option.class).split(); }
            if (field.isAnnotationPresent(Parameters.class)) { return field.getAnnotation(Parameters.class).split(); }
            return "";
        }
        private String[] split(String value, Field field) {
            String regex = splitRegex(field);
            return regex.length() == 0 ? new String[] {value} : value.split(regex);
        }

        /**
         * Called when parsing varargs parameters for a multi-value option.
         * When an option is encountered, the remainder should not be interpreted as vararg elements.
         * @param arg the string to determine whether it is an option or not
         * @return true if it is an option, false otherwise
         */
        private boolean isOption(String arg) {
            if ("--".equals(arg)) {
                return true;
            }
            // not just arg prefix: we may be in the middle of parsing -xrvfFILE
            if (optionName2Field.containsKey(arg)) { // -v or -f or --file (not attached to param or other option)
                return true;
            }
            int separatorIndex = arg.indexOf(separator);
            if (separatorIndex > 0) { // -f=FILE or --file==FILE (attached to param via separator)
                if (optionName2Field.containsKey(arg.substring(0, separatorIndex))) {
                    return true;
                }
            }
            return (arg.length() > 2 && arg.startsWith("-") && singleCharOption2Field.containsKey(arg.charAt(1)));
        }
        private Object tryConvert(Field field, int index, ITypeConverter<?> converter, String value, Class<?> type)
                throws Exception {
            try {
                return converter.convert(value);
            } catch (ParameterException ex) {
                throw new ParameterException(ex.getMessage() + optionDescription(" for ", field, index));
            } catch (Exception other) {
                String desc = optionDescription(" for ", field, index) + ": " + other;
                throw new ParameterException("Could not convert '" + value + "' to " + type.getSimpleName() + desc, other);
            }
        }

        private String optionDescription(String prefix, Field field, int index) {
            Help.IParamLabelRenderer labelRenderer = Help.createMinimalParamLabelRenderer();
            String desc = "";
            if (field.isAnnotationPresent(Option.class)) {
                desc = prefix + "option '" + field.getAnnotation(Option.class).names()[0] + "'";
                if (index >= 0) {
                    Range arity = Range.optionArity(field);
                    if (arity.max > 1) {
                        desc += " at index " + index;
                    }
                    desc += " (" + labelRenderer.renderParameterLabel(field, Help.Ansi.OFF, Collections.<IStyle>emptyList()) + ")";
                }
            } else if (field.isAnnotationPresent(Parameters.class)) {
                Range indexRange = Range.parameterIndex(field);
                Text label = labelRenderer.renderParameterLabel(field, Help.Ansi.OFF, Collections.<IStyle>emptyList());
                desc = prefix + "positional parameter at index " + indexRange + " (" + label + ")";
            }
            return desc;
        }

        private Class<?>[] getTypeAttribute(Field field) {
            if (field.isAnnotationPresent(Parameters.class)) {
                return field.getAnnotation(Parameters.class).type();
            } else if (field.isAnnotationPresent(Option.class)) {
                return field.getAnnotation(Option.class).type();
            }
            throw new IllegalStateException(field + " has neither @Parameters nor @Option annotation");
        }

        private boolean isAnyHelpRequested() { return isHelpRequested || versionHelpRequested || usageHelpRequested; }

        private void updateHelpRequested(Field field) {
            if (field.isAnnotationPresent(Option.class)) {
                isHelpRequested                       |= is(field, "help", field.getAnnotation(Option.class).help());
                CommandLine.this.versionHelpRequested |= is(field, "versionHelp", field.getAnnotation(Option.class).versionHelp());
                CommandLine.this.usageHelpRequested   |= is(field, "usageHelp", field.getAnnotation(Option.class).usageHelp());
            }
        }
        private boolean is(Field f, String description, boolean value) {
            if (value) { tracer.info("Field '%s.%s' has '%s' annotation: not validating required fields%n", f.getDeclaringClass().getSimpleName(), f.getName(), description); }
            return value;
        }
        @SuppressWarnings("unchecked")
        private Collection<Object> createCollection(Class<?> collectionClass) throws Exception {
            if (collectionClass.isInterface()) {
                if (List.class.isAssignableFrom(collectionClass)) {
                    return new ArrayList<Object>();
                } else if (SortedSet.class.isAssignableFrom(collectionClass)) {
                    return new TreeSet<Object>();
                } else if (Set.class.isAssignableFrom(collectionClass)) {
                    return new HashSet<Object>();
                } else if (Queue.class.isAssignableFrom(collectionClass)) {
                    return new LinkedList<Object>(); // ArrayDeque is only available since 1.6
                }
                return new ArrayList<Object>();
            }
            // custom Collection implementation class must have default constructor
            return (Collection<Object>) collectionClass.newInstance();
        }
        private Map<Object, Object> createMap(Class<?> mapClass) throws Exception {
            try { // if it is an implementation class, instantiate it
                return (Map<Object, Object>) mapClass.newInstance();
            } catch (Exception ignored) {}
            return new LinkedHashMap<Object, Object>();
        }
        private ITypeConverter<?> getTypeConverter(final Class<?> type, Field field) {
            ITypeConverter<?> result = converterRegistry.get(type);
            if (result != null) {
                return result;
            }
            if (type.isEnum()) {
                return new ITypeConverter<Object>() {
                    @SuppressWarnings("unchecked")
                    public Object convert(String value) throws Exception {
                        return Enum.valueOf((Class<Enum>) type, value);
                    }
                };
            }
            throw new MissingTypeConverterException("No TypeConverter registered for " + type.getName() + " of field " + field);
        }

        private void assertNoMissingParameters(Field field, int arity, Stack<String> args) {
            if (arity > args.size()) {
                int actualSize = 0;
                @SuppressWarnings("unchecked")
                Stack<String> copy = (Stack<String>) args.clone();
                while (!copy.isEmpty()) {
                    actualSize += split(copy.pop(), field).length;
                    if (actualSize >= arity) { return; }
                }
                if (arity == 1) {
                    if (field.isAnnotationPresent(Option.class)) {
                        throw new MissingParameterException("Missing required parameter for " +
                                optionDescription("", field, 0));
                    }
                    Range indexRange = Range.parameterIndex(field);
                    Help.IParamLabelRenderer labelRenderer = Help.createMinimalParamLabelRenderer();
                    String sep = "";
                    String names = "";
                    int count = 0;
                    for (int i = indexRange.min; i < positionalParametersFields.size(); i++) {
                        if (Range.parameterArity(positionalParametersFields.get(i)).min > 0) {
                            names += sep + labelRenderer.renderParameterLabel(positionalParametersFields.get(i),
                                    Help.Ansi.OFF, Collections.<IStyle>emptyList());
                            sep = ", ";
                            count++;
                        }
                    }
                    String msg = "Missing required parameter";
                    Range paramArity = Range.parameterArity(field);
                    if (paramArity.isVariable) {
                        msg += "s at positions " + indexRange + ": ";
                    } else {
                        msg += (count > 1 ? "s: " : ": ");
                    }
                    throw new MissingParameterException(msg + names);
                }
                throw new MissingParameterException(optionDescription("", field, 0) +
                        " requires at least " + arity + " values, but only " + args.size() + " were specified.");
            }
        }
        private String trim(String value) {
            return unquote(value);
        }

        private String unquote(String value) {
            return value == null
                    ? null
                    : (value.length() > 1 && value.startsWith("\"") && value.endsWith("\""))
                        ? value.substring(1, value.length() - 1)
                        : value;
        }
    }
    private static class PositionalParametersSorter implements Comparator<Field> {
        public int compare(Field o1, Field o2) {
            int result = Range.parameterIndex(o1).compareTo(Range.parameterIndex(o2));
            return (result == 0) ? Range.parameterArity(o1).compareTo(Range.parameterArity(o2)) : result;
        }
    }
    /**
     * Inner class to group the built-in {@link ITypeConverter} implementations.
     */
    private static class BuiltIn {
        static class StringConverter implements ITypeConverter<String> {
            public String convert(String value) { return value; }
        }
        static class StringBuilderConverter implements ITypeConverter<StringBuilder> {
            public StringBuilder convert(String value) { return new StringBuilder(value); }
        }
        static class CharSequenceConverter implements ITypeConverter<CharSequence> {
            public String convert(String value) { return value; }
        }
        /** Converts text to a {@code Byte} by delegating to {@link Byte#valueOf(String)}.*/
        static class ByteConverter implements ITypeConverter<Byte> {
            public Byte convert(String value) { return Byte.valueOf(value); }
        }
        /** Converts {@code "true"} or {@code "false"} to a {@code Boolean}. Other values result in a ParameterException.*/
        static class BooleanConverter implements ITypeConverter<Boolean> {
            public Boolean convert(String value) {
                if ("true".equalsIgnoreCase(value) || "false".equalsIgnoreCase(value)) {
                    return Boolean.parseBoolean(value);
                } else {
                    throw new ParameterException("'" + value + "' is not a boolean");
                }
            }
        }
        static class CharacterConverter implements ITypeConverter<Character> {
            public Character convert(String value) {
                if (value.length() > 1) {
                    throw new ParameterException("'" + value + "' is not a single character");
                }
                return value.charAt(0);
            }
        }
        /** Converts text to a {@code Short} by delegating to {@link Short#valueOf(String)}.*/
        static class ShortConverter implements ITypeConverter<Short> {
            public Short convert(String value) { return Short.valueOf(value); }
        }
        /** Converts text to an {@code Integer} by delegating to {@link Integer#valueOf(String)}.*/
        static class IntegerConverter implements ITypeConverter<Integer> {
            public Integer convert(String value) { return Integer.valueOf(value); }
        }
        /** Converts text to a {@code Long} by delegating to {@link Long#valueOf(String)}.*/
        static class LongConverter implements ITypeConverter<Long> {
            public Long convert(String value) { return Long.valueOf(value); }
        }
        static class FloatConverter implements ITypeConverter<Float> {
            public Float convert(String value) { return Float.valueOf(value); }
        }
        static class DoubleConverter implements ITypeConverter<Double> {
            public Double convert(String value) { return Double.valueOf(value); }
        }
        static class FileConverter implements ITypeConverter<File> {
            public File convert(String value) { return new File(value); }
        }
        static class URLConverter implements ITypeConverter<URL> {
            public URL convert(String value) throws MalformedURLException { return new URL(value); }
        }
        static class URIConverter implements ITypeConverter<URI> {
            public URI convert(String value) throws URISyntaxException { return new URI(value); }
        }
        /** Converts text in {@code yyyy-mm-dd} format to a {@code java.util.Date}. ParameterException on failure. */
        static class ISO8601DateConverter implements ITypeConverter<Date> {
            public Date convert(String value) {
                try {
                    return new SimpleDateFormat("yyyy-MM-dd").parse(value);
                } catch (ParseException e) {
                    throw new ParameterException("'" + value + "' is not a yyyy-MM-dd date");
                }
            }
        }
        /** Converts text in any of the following formats to a {@code java.sql.Time}: {@code HH:mm}, {@code HH:mm:ss},
         * {@code HH:mm:ss.SSS}, {@code HH:mm:ss,SSS}. Other formats result in a ParameterException. */
        static class ISO8601TimeConverter implements ITypeConverter<Time> {
            public Time convert(String value) {
                try {
                    if (value.length() <= 5) {
                        return new Time(new SimpleDateFormat("HH:mm").parse(value).getTime());
                    } else if (value.length() <= 8) {
                        return new Time(new SimpleDateFormat("HH:mm:ss").parse(value).getTime());
                    } else if (value.length() <= 12) {
                        try {
                            return new Time(new SimpleDateFormat("HH:mm:ss.SSS").parse(value).getTime());
                        } catch (ParseException e2) {
                            return new Time(new SimpleDateFormat("HH:mm:ss,SSS").parse(value).getTime());
                        }
                    }
                } catch (ParseException ignored) {
                    // ignored because we throw a ParameterException below
                }
                throw new ParameterException("'" + value + "' is not a HH:mm[:ss[.SSS]] time");
            }
        }
        static class BigDecimalConverter implements ITypeConverter<BigDecimal> {
            public BigDecimal convert(String value) { return new BigDecimal(value); }
        }
        static class BigIntegerConverter implements ITypeConverter<BigInteger> {
            public BigInteger convert(String value) { return new BigInteger(value); }
        }
        static class CharsetConverter implements ITypeConverter<Charset> {
            public Charset convert(String s) { return Charset.forName(s); }
        }
        /** Converts text to a {@code InetAddress} by delegating to {@link InetAddress#getByName(String)}. */
        static class InetAddressConverter implements ITypeConverter<InetAddress> {
            public InetAddress convert(String s) throws Exception { return InetAddress.getByName(s); }
        }
        static class PatternConverter implements ITypeConverter<Pattern> {
            public Pattern convert(String s) { return Pattern.compile(s); }
        }
        static class UUIDConverter implements ITypeConverter<UUID> {
            public UUID convert(String s) throws Exception { return UUID.fromString(s); }
        }
        private BuiltIn() {} // private constructor: never instantiate
    }

    /**
     * A collection of methods and inner classes that provide fine-grained control over the contents and layout of
     * the usage help message to display to end users when help is requested or invalid input values were specified.
     * <h3>Layered API</h3>
     * <p>The {@link Command} annotation provides the easiest way to customize usage help messages. See
     * the <a href="https://remkop.github.io/picocli/index.html#_usage_help">Manual</a> for details.</p>
     * <p>This Help class provides high-level functions to create sections of the usage help message and headings
     * for these sections. Instead of calling the {@link CommandLine#usage(PrintStream, CommandLine.Help.ColorScheme)}
     * method, application authors may want to create a custom usage help message by reorganizing sections in a
     * different order and/or adding custom sections.</p>
     * <p>Finally, the Help class contains inner classes and interfaces that can be used to create custom help messages.</p>
     * <h4>IOptionRenderer and IParameterRenderer</h4>
     * <p>Renders a field annotated with {@link Option} or {@link Parameters} to an array of {@link Text} values.
     * By default, these values are</p><ul>
     * <li>mandatory marker character (if the option/parameter is {@link Option#required() required})</li>
     * <li>short option name (empty for parameters)</li>
     * <li>comma or empty (empty for parameters)</li>
     * <li>long option names (the parameter {@link IParamLabelRenderer label} for parameters)</li>
     * <li>description</li>
     * </ul>
     * <p>Other components rely on this ordering.</p>
     * <h4>Layout</h4>
     * <p>Delegates to the renderers to create {@link Text} values for the annotated fields, and uses a
     * {@link TextTable} to display these values in tabular format. Layout is responsible for deciding which values
     * to display where in the table. By default, Layout shows one option or parameter per table row.</p>
     * <h4>TextTable</h4>
     * <p>Responsible for spacing out {@link Text} values according to the {@link Column} definitions the table was
     * created with. Columns have a width, indentation, and an overflow policy that decides what to do if a value is
     * longer than the column's width.</p>
     * <h4>Text</h4>
     * <p>Encapsulates rich text with styles and colors in a way that other components like {@link TextTable} are
     * unaware of the embedded ANSI escape codes.</p>
     */
    public static class Help {
        /** Constant String holding the default program name: {@value} */
        protected static final String DEFAULT_COMMAND_NAME = "<main class>";

        private final static int usageHelpWidth = 80;
        private final static int optionsColumnWidth = 2 + 2 + 1 + 24;
        private final Object command;
        private final Map<String, Help> commands = new LinkedHashMap<String, Help>();
        final ColorScheme colorScheme;

        /** Immutable list of fields annotated with {@link Option}, in declaration order. */
        public final List<Field> optionFields;

        /** Immutable list of fields annotated with {@link Parameters}, or an empty list if no such field exists. */
        public final List<Field> positionalParametersFields;

        /** The String to use as the separator between options and option parameters. {@code "="} by default,
         * initialized from {@link Command#separator()} if defined. */
        public String separator;

        /** The String to use as the program name in the synopsis line of the help message.
         * {@link #DEFAULT_COMMAND_NAME} by default, initialized from {@link Command#name()} if defined. */
        public String commandName = DEFAULT_COMMAND_NAME;

        /** Optional text lines to use as the description of the help message, displayed between the synopsis and the
         * options list. Initialized from {@link Command#description()} if the {@code Command} annotation is present,
         * otherwise this is an empty array and the help message has no description.
         * Applications may programmatically set this field to create a custom help message. */
        public String[] description = {};

        /** Optional custom synopsis lines to use instead of the auto-generated synopsis.
         * Initialized from {@link Command#customSynopsis()} if the {@code Command} annotation is present,
         * otherwise this is an empty array and the synopsis is generated.
         * Applications may programmatically set this field to create a custom help message. */
        public String[] customSynopsis = {};

        /** Optional header lines displayed at the top of the help message. For subcommands, the first header line is
         * displayed in the list of commands. Values are initialized from {@link Command#header()}
         * if the {@code Command} annotation is present, otherwise this is an empty array and the help message has no
         * header. Applications may programmatically set this field to create a custom help message. */
        public String[] header = {};

        /** Optional footer text lines displayed at the bottom of the help message. Initialized from
         * {@link Command#footer()} if the {@code Command} annotation is present, otherwise this is an empty array and
         * the help message has no footer.
         * Applications may programmatically set this field to create a custom help message. */
        public String[] footer = {};

        /** Option and positional parameter value label renderer used for the synopsis line(s) and the option list. */
        public IParamLabelRenderer parameterLabelRenderer;

        /** If {@code true}, the synopsis line(s) will show an abbreviated synopsis without detailed option names. */
        public Boolean abbreviateSynopsis;

        /** If {@code true}, the options list is sorted alphabetically. */
        public Boolean sortOptions;

        /** If {@code true}, the options list will show default values for all options except booleans. */
        public Boolean showDefaultValues;

        /** Character used to prefix required options in the options list. */
        public Character requiredOptionMarker;

        /** Optional heading preceding the header section. Initialized from {@link Command#headerHeading()}, or null. */
        public String headerHeading;

        /** Optional heading preceding the synopsis. Initialized from {@link Command#synopsisHeading()}, {@code "Usage: "} by default. */
        public String synopsisHeading;

        /** Optional heading preceding the description section. Initialized from {@link Command#descriptionHeading()}, or null. */
        public String descriptionHeading;

        /** Optional heading preceding the parameter list. Initialized from {@link Command#parameterListHeading()}, or null. */
        public String parameterListHeading;

        /** Optional heading preceding the options list. Initialized from {@link Command#optionListHeading()}, or null. */
        public String optionListHeading;

        /** Optional heading preceding the subcommand list. Initialized from {@link Command#commandListHeading()}. {@code "Commands:%n"} by default. */
        public String commandListHeading;

        /** Optional heading preceding the footer section. Initialized from {@link Command#footerHeading()}, or null. */
        public String footerHeading;

        /** Constructs a new {@code Help} instance with a default color scheme, initialized from annotatations
         * on the specified class and superclasses.
         * @param command the annotated object to create usage help for */
        public Help(Object command) {
            this(command, Ansi.AUTO);
        }

        /** Constructs a new {@code Help} instance with a default color scheme, initialized from annotatations
         * on the specified class and superclasses.
         * @param command the annotated object to create usage help for
         * @param ansi whether to emit ANSI escape codes or not */
        public Help(Object command, Ansi ansi) {
            this(command, defaultColorScheme(ansi));
        }

        /** Constructs a new {@code Help} instance with the specified color scheme, initialized from annotatations
         * on the specified class and superclasses.
         * @param command the annotated object to create usage help for
         * @param colorScheme the color scheme to use */
        public Help(Object command, ColorScheme colorScheme) {
            this.command = Assert.notNull(command, "command");
            this.colorScheme = Assert.notNull(colorScheme, "colorScheme").applySystemProperties();
            List<Field> options = new ArrayList<Field>();
            List<Field> operands = new ArrayList<Field>();
            Class<?> cls = command.getClass();
            while (cls != null) {
                for (Field field : cls.getDeclaredFields()) {
                    field.setAccessible(true);
                    if (field.isAnnotationPresent(Option.class)) {
                        Option option = field.getAnnotation(Option.class);
                        if (!option.hidden()) { // hidden options should not appear in usage help
                            // TODO remember longest concatenated option string length (issue #45)
                            options.add(field);
                        }
                    }
                    if (field.isAnnotationPresent(Parameters.class)) {
                        operands.add(field);
                    }
                }
                // superclass values should not overwrite values if both class and superclass have a @Command annotation
                if (cls.isAnnotationPresent(Command.class)) {
                    Command cmd = cls.getAnnotation(Command.class);
                    if (DEFAULT_COMMAND_NAME.equals(commandName)) {
                        commandName = cmd.name();
                    }
                    separator = (separator == null) ? cmd.separator() : separator;
                    abbreviateSynopsis = (abbreviateSynopsis == null) ? cmd.abbreviateSynopsis() : abbreviateSynopsis;
                    sortOptions = (sortOptions == null) ? cmd.sortOptions() : sortOptions;
                    requiredOptionMarker = (requiredOptionMarker == null) ? cmd.requiredOptionMarker() : requiredOptionMarker;
                    showDefaultValues = (showDefaultValues == null) ? cmd.showDefaultValues() : showDefaultValues;
                    customSynopsis = empty(customSynopsis) ? cmd.customSynopsis() : customSynopsis;
                    description = empty(description) ? cmd.description() : description;
                    header = empty(header) ? cmd.header() : header;
                    footer = empty(footer) ? cmd.footer() : footer;
                    headerHeading = empty(headerHeading) ? cmd.headerHeading() : headerHeading;
                    synopsisHeading = empty(synopsisHeading) || "Usage: ".equals(synopsisHeading) ? cmd.synopsisHeading() : synopsisHeading;
                    descriptionHeading = empty(descriptionHeading) ? cmd.descriptionHeading() : descriptionHeading;
                    parameterListHeading = empty(parameterListHeading) ? cmd.parameterListHeading() : parameterListHeading;
                    optionListHeading = empty(optionListHeading) ? cmd.optionListHeading() : optionListHeading;
                    commandListHeading = empty(commandListHeading) || "Commands:%n".equals(commandListHeading) ? cmd.commandListHeading() : commandListHeading;
                    footerHeading = empty(footerHeading) ? cmd.footerHeading() : footerHeading;
                }
                cls = cls.getSuperclass();
            }
            sortOptions =          (sortOptions == null)          ? true : sortOptions;
            abbreviateSynopsis =   (abbreviateSynopsis == null)   ? false : abbreviateSynopsis;
            requiredOptionMarker = (requiredOptionMarker == null) ? ' ' : requiredOptionMarker;
            showDefaultValues =    (showDefaultValues == null)    ? false : showDefaultValues;
            synopsisHeading =      (synopsisHeading == null)      ? "Usage: " : synopsisHeading;
            commandListHeading =   (commandListHeading == null)   ? "Commands:%n" : commandListHeading;
            separator =            (separator == null)            ? "=" : separator;
            parameterLabelRenderer = new DefaultParamLabelRenderer(separator);
            Collections.sort(operands, new PositionalParametersSorter());
            positionalParametersFields = Collections.unmodifiableList(operands);
            optionFields                 = Collections.unmodifiableList(options);
        }

        /** Registers all specified subcommands with this Help.
         * @param commands maps the command names to the associated CommandLine object
         * @return this Help instance (for method chaining)
         * @see CommandLine#getSubcommands()
         */
        public Help addAllSubcommands(Map<String, CommandLine> commands) {
            if (commands != null) {
                for (Map.Entry<String, CommandLine> entry : commands.entrySet()) {
                    addSubcommand(entry.getKey(), entry.getValue().getCommand());
                }
            }
            return this;
        }

        /** Registers the specified subcommand with this Help.
         * @param commandName the name of the subcommand to display in the usage message
         * @param command the annotated object to get more information from
         * @return this Help instance (for method chaining)
         */
        public Help addSubcommand(String commandName, Object command) {
            commands.put(commandName, new Help(command));
            return this;
        }

        /** Returns a synopsis for the command without reserving space for the synopsis heading.
         * @return a synopsis
         * @see #abbreviatedSynopsis()
         * @see #detailedSynopsis(Comparator, boolean)
         * @deprecated use {@link #synopsis(int)} instead
         */
        public String synopsis() { return synopsis(0); }

        /**
         * Returns a synopsis for the command, reserving the specified space for the synopsis heading.
         * @param synopsisHeadingLength the length of the synopsis heading that will be displayed on the same line
         * @return a synopsis
         * @see #abbreviatedSynopsis()
         * @see #detailedSynopsis(Comparator, boolean)
         * @see #synopsisHeading
         */
        public String synopsis(int synopsisHeadingLength) {
            if (!empty(customSynopsis)) { return customSynopsis(); }
            return abbreviateSynopsis ? abbreviatedSynopsis()
                    : detailedSynopsis(synopsisHeadingLength, createShortOptionArityAndNameComparator(), true);
        }

        /** Generates a generic synopsis like {@code <command name> [OPTIONS] [PARAM1 [PARAM2]...]}, omitting parts
         * that don't apply to the command (e.g., does not show [OPTIONS] if the command has no options).
         * @return a generic synopsis */
        public String abbreviatedSynopsis() {
            StringBuilder sb = new StringBuilder();
            if (!optionFields.isEmpty()) { // only show if annotated object actually has options
                sb.append(" [OPTIONS]");
            }
            // sb.append(" [--] "); // implied
            for (Field positionalParam : positionalParametersFields) {
                if (!positionalParam.getAnnotation(Parameters.class).hidden()) {
                    sb.append(' ').append(parameterLabelRenderer.renderParameterLabel(positionalParam, ansi(), colorScheme.parameterStyles));
                }
            }
            return colorScheme.commandText(commandName).toString()
                    + (sb.toString()) + System.getProperty("line.separator");
        }
        /** Generates a detailed synopsis message showing all options and parameters. Follows the unix convention of
         * showing optional options and parameters in square brackets ({@code [ ]}).
         * @param optionSort comparator to sort options or {@code null} if options should not be sorted
         * @param clusterBooleanOptions {@code true} if boolean short options should be clustered into a single string
         * @return a detailed synopsis
         * @deprecated use {@link #detailedSynopsis(int, Comparator, boolean)} instead. */
        public String detailedSynopsis(Comparator<Field> optionSort, boolean clusterBooleanOptions) {
            return detailedSynopsis(0, optionSort, clusterBooleanOptions);
        }

        /** Generates a detailed synopsis message showing all options and parameters. Follows the unix convention of
         * showing optional options and parameters in square brackets ({@code [ ]}).
         * @param synopsisHeadingLength the length of the synopsis heading that will be displayed on the same line
         * @param optionSort comparator to sort options or {@code null} if options should not be sorted
         * @param clusterBooleanOptions {@code true} if boolean short options should be clustered into a single string
         * @return a detailed synopsis */
        public String detailedSynopsis(int synopsisHeadingLength, Comparator<Field> optionSort, boolean clusterBooleanOptions) {
            Text optionText = ansi().new Text(0);
            List<Field> fields = new ArrayList<Field>(optionFields); // iterate in declaration order
            if (optionSort != null) {
                Collections.sort(fields, optionSort);// iterate in specified sort order
            }
            if (clusterBooleanOptions) { // cluster all short boolean options into a single string
                List<Field> booleanOptions = new ArrayList<Field>();
                StringBuilder clusteredRequired = new StringBuilder("-");
                StringBuilder clusteredOptional = new StringBuilder("-");
                for (Field field : fields) {
                    if (field.getType() == boolean.class || field.getType() == Boolean.class) {
                        Option option = field.getAnnotation(Option.class);
                        String shortestName = ShortestFirst.sort(option.names())[0];
                        if (shortestName.length() == 2 && shortestName.startsWith("-")) {
                            booleanOptions.add(field);
                            if (option.required()) {
                                clusteredRequired.append(shortestName.substring(1));
                            } else {
                                clusteredOptional.append(shortestName.substring(1));
                            }
                        }
                    }
                }
                fields.removeAll(booleanOptions);
                if (clusteredRequired.length() > 1) { // initial length was 1
                    optionText = optionText.append(" ").append(colorScheme.optionText(clusteredRequired.toString()));
                }
                if (clusteredOptional.length() > 1) { // initial length was 1
                    optionText = optionText.append(" [").append(colorScheme.optionText(clusteredOptional.toString())).append("]");
                }
            }
            for (Field field : fields) {
                Option option = field.getAnnotation(Option.class);
                if (!option.hidden()) {
                    //sb.append(" ");
                    optionText = optionText.append(option.required() ? " " : " [");

                    String optionNames = ShortestFirst.sort(option.names())[0];
                    optionText = optionText.append(colorScheme.optionText(optionNames));

                    Text optionParamText = parameterLabelRenderer.renderParameterLabel(field, colorScheme.ansi(), colorScheme.optionParamStyles);
                    optionText = optionText.append(optionParamText);
                    if (!option.required()) {
                        optionText = optionText.append("]");
                    }
                }
            }
            for (Field positionalParam : positionalParametersFields) {
                if (!positionalParam.getAnnotation(Parameters.class).hidden()) {
                    optionText = optionText.append(" ");
                    Text label = parameterLabelRenderer.renderParameterLabel(positionalParam, colorScheme.ansi(), colorScheme.parameterStyles);
                    optionText = optionText.append(label);
                }
            }
            // Fix for #142: first line of synopsis overshoots max. characters
            int firstColumnLength = commandName.length() + synopsisHeadingLength;

            // synopsis heading ("Usage: ") may be on the same line, so adjust column width
            TextTable textTable = new TextTable(ansi(), firstColumnLength, usageHelpWidth - firstColumnLength);
            textTable.indentWrappedLines = 1; // don't worry about first line: options (2nd column) always start with a space

            // right-adjust the command name by length of synopsis heading
            Text PADDING = Ansi.OFF.new Text(spaces(synopsisHeadingLength));
            textTable.addRowValues(new Text[] {PADDING.append(colorScheme.commandText(commandName)), optionText});
            return textTable.toString().substring(synopsisHeadingLength); // cut off leading synopsis heading spaces
        }
        /** Returns the number of characters the synopsis heading will take on the same line as the synopsis.
         * @return the number of characters the synopsis heading will take on the same line as the synopsis.
         * @see #detailedSynopsis(int, Comparator, boolean)
         */
        public int synopsisHeadingLength() {
            String[] lines = Ansi.OFF.new Text(synopsisHeading).toString().split("\\r?\\n|\\r|%n", -1);
            return lines[lines.length - 1].length();
        }
        /**
         * <p>Returns a description of the {@linkplain Option options} supported by the application.
         * This implementation {@linkplain #createShortOptionNameComparator() sorts options alphabetically}, and shows
         * only the {@linkplain Option#hidden() non-hidden} options in a {@linkplain TextTable tabular format}
         * using the {@linkplain #createDefaultOptionRenderer() default renderer} and {@linkplain Layout default layout}.</p>
         * @return the fully formatted option list
         * @see #optionList(Layout, Comparator, IParamLabelRenderer)
         */
        public String optionList() {
            Comparator<Field> sortOrder = sortOptions == null || sortOptions.booleanValue()
                    ? createShortOptionNameComparator()
                    : null;
            return optionList(createDefaultLayout(), sortOrder, createDefaultParamLabelRenderer());
        }

        /** Sorts all {@code Options} with the specified {@code comparator} (if the comparator is non-{@code null}),
         * then {@linkplain Layout#addOption(Field, CommandLine.Help.IParamLabelRenderer) adds} all non-hidden options to the
         * specified TextTable and returns the result of TextTable.toString().
         * @param layout responsible for rendering the option list
         * @param optionSort determines in what order {@code Options} should be listed. Declared order if {@code null}
         * @param valueLabelRenderer used for options with a parameter
         * @return the fully formatted option list
         */
        public String optionList(Layout layout, Comparator<Field> optionSort, IParamLabelRenderer valueLabelRenderer) {
            List<Field> fields = new ArrayList<Field>(optionFields); // options are stored in order of declaration
            if (optionSort != null) {
                Collections.sort(fields, optionSort); // default: sort options ABC
            }
            layout.addOptions(fields, valueLabelRenderer);
            return layout.toString();
        }

        /**
         * Returns the section of the usage help message that lists the parameters with their descriptions.
         * @return the section of the usage help message that lists the parameters
         */
        public String parameterList() {
            return parameterList(createDefaultLayout(), createMinimalParamLabelRenderer());
        }
        /**
         * Returns the section of the usage help message that lists the parameters with their descriptions.
         * @param layout the layout to use
         * @param paramLabelRenderer for rendering parameter names
         * @return the section of the usage help message that lists the parameters
         */
        public String parameterList(Layout layout, IParamLabelRenderer paramLabelRenderer) {
            layout.addPositionalParameters(positionalParametersFields, paramLabelRenderer);
            return layout.toString();
        }

        /** Formats each of the specified values and appends it to the specified StringBuilder.
         * @param ansi whether the result should contain ANSI escape codes or not
         * @param values the values to format and append to the StringBuilder
         * @param sb the StringBuilder to collect the formatted strings
         * @param params the parameters to pass to the format method when formatting each value
         * @return the specified StringBuilder */
        public static StringBuilder join(Ansi ansi, String[] values, StringBuilder sb, Object... params) {
            if (values != null) {
                TextTable table = new TextTable(ansi, usageHelpWidth);
                table.indentWrappedLines = 0;
                for (String summaryLine : values) {
                    table.addRowValues(ansi.new Text(String.format(summaryLine, params)));
                }
                table.toString(sb);
            }
            return sb;
        }
        /** Returns command custom synopsis as a string. A custom synopsis can be zero or more lines, and can be
         * specified declaratively with the {@link Command#customSynopsis()} annotation attribute or programmatically
         * by setting the Help instance's {@link Help#customSynopsis} field.
         * @param params Arguments referenced by the format specifiers in the synopsis strings
         * @return the custom synopsis lines combined into a single String (which may be empty)
         */
        public String customSynopsis(Object... params) {
            return join(ansi(), customSynopsis, new StringBuilder(), params).toString();
        }
        /** Returns command description text as a string. Description text can be zero or more lines, and can be specified
         * declaratively with the {@link Command#description()} annotation attribute or programmatically by
         * setting the Help instance's {@link Help#description} field.
         * @param params Arguments referenced by the format specifiers in the description strings
         * @return the description lines combined into a single String (which may be empty)
         */
        public String description(Object... params) {
            return join(ansi(), description, new StringBuilder(), params).toString();
        }
        /** Returns the command header text as a string. Header text can be zero or more lines, and can be specified
         * declaratively with the {@link Command#header()} annotation attribute or programmatically by
         * setting the Help instance's {@link Help#header} field.
         * @param params Arguments referenced by the format specifiers in the header strings
         * @return the header lines combined into a single String (which may be empty)
         */
        public String header(Object... params) {
            return join(ansi(), header, new StringBuilder(), params).toString();
        }
        /** Returns command footer text as a string. Footer text can be zero or more lines, and can be specified
         * declaratively with the {@link Command#footer()} annotation attribute or programmatically by
         * setting the Help instance's {@link Help#footer} field.
         * @param params Arguments referenced by the format specifiers in the footer strings
         * @return the footer lines combined into a single String (which may be empty)
         */
        public String footer(Object... params) {
            return join(ansi(), footer, new StringBuilder(), params).toString();
        }

        /** Returns the text displayed before the header text; the result of {@code String.format(headerHeading, params)}.
         * @param params the parameters to use to format the header heading
         * @return the formatted header heading */
        public String headerHeading(Object... params) {
            return ansi().new Text(format(headerHeading, params)).toString();
        }

        /** Returns the text displayed before the synopsis text; the result of {@code String.format(synopsisHeading, params)}.
         * @param params the parameters to use to format the synopsis heading
         * @return the formatted synopsis heading */
        public String synopsisHeading(Object... params) {
            return ansi().new Text(format(synopsisHeading, params)).toString();
        }

        /** Returns the text displayed before the description text; an empty string if there is no description,
         * otherwise the result of {@code String.format(descriptionHeading, params)}.
         * @param params the parameters to use to format the description heading
         * @return the formatted description heading */
        public String descriptionHeading(Object... params) {
            return empty(descriptionHeading) ? "" : ansi().new Text(format(descriptionHeading, params)).toString();
        }

        /** Returns the text displayed before the positional parameter list; an empty string if there are no positional
         * parameters, otherwise the result of {@code String.format(parameterListHeading, params)}.
         * @param params the parameters to use to format the parameter list heading
         * @return the formatted parameter list heading */
        public String parameterListHeading(Object... params) {
            return positionalParametersFields.isEmpty() ? "" : ansi().new Text(format(parameterListHeading, params)).toString();
        }

        /** Returns the text displayed before the option list; an empty string if there are no options,
         * otherwise the result of {@code String.format(optionListHeading, params)}.
         * @param params the parameters to use to format the option list heading
         * @return the formatted option list heading */
        public String optionListHeading(Object... params) {
            return optionFields.isEmpty() ? "" : ansi().new Text(format(optionListHeading, params)).toString();
        }

        /** Returns the text displayed before the command list; an empty string if there are no commands,
         * otherwise the result of {@code String.format(commandListHeading, params)}.
         * @param params the parameters to use to format the command list heading
         * @return the formatted command list heading */
        public String commandListHeading(Object... params) {
            return commands.isEmpty() ? "" : ansi().new Text(format(commandListHeading, params)).toString();
        }

        /** Returns the text displayed before the footer text; the result of {@code String.format(footerHeading, params)}.
         * @param params the parameters to use to format the footer heading
         * @return the formatted footer heading */
        public String footerHeading(Object... params) {
            return ansi().new Text(format(footerHeading, params)).toString();
        }
        private String format(String formatString,  Object[] params) {
            return formatString == null ? "" : String.format(formatString, params);
        }
        /** Returns a 2-column list with command names and the first line of their header or (if absent) description.
         * @return a usage help section describing the added commands */
        public String commandList() {
            if (commands.isEmpty()) { return ""; }
            int commandLength = maxLength(commands.keySet());
            Help.TextTable textTable = new Help.TextTable(ansi(),
                    new Help.Column(commandLength + 2, 2, Help.Column.Overflow.SPAN),
                    new Help.Column(usageHelpWidth - (commandLength + 2), 2, Help.Column.Overflow.WRAP));

            for (Map.Entry<String, Help> entry : commands.entrySet()) {
                Help command = entry.getValue();
                String header = command.header != null && command.header.length > 0 ? command.header[0]
                        : (command.description != null && command.description.length > 0 ? command.description[0] : "");
                textTable.addRowValues(colorScheme.commandText(entry.getKey()), ansi().new Text(header));
            }
            return textTable.toString();
        }
        private static int maxLength(Collection<String> any) {
            List<String> strings = new ArrayList<String>(any);
            Collections.sort(strings, Collections.reverseOrder(Help.shortestFirst()));
            return strings.get(0).length();
        }
        private static String join(String[] names, int offset, int length, String separator) {
            if (names == null) { return ""; }
            StringBuilder result = new StringBuilder();
            for (int i = offset; i < offset + length; i++) {
                result.append((i > offset) ? separator : "").append(names[i]);
            }
            return result.toString();
        }
        private static String spaces(int length) {
            char[] buff = new char[length];
            Arrays.fill(buff, ' ');
            return new String(buff);
        }

        /** Returns a {@code Layout} instance configured with the user preferences captured in this Help instance.
         * @return a Layout */
        public Layout createDefaultLayout() {
            return new Layout(colorScheme, new TextTable(colorScheme.ansi()), createDefaultOptionRenderer(), createDefaultParameterRenderer());
        }
        /** Returns a new default OptionRenderer which converts {@link Option Options} to five columns of text to match
         *  the default {@linkplain TextTable TextTable} column layout. The first row of values looks like this:
         * <ol>
         * <li>the required option marker</li>
         * <li>2-character short option name (or empty string if no short option exists)</li>
         * <li>comma separator (only if both short option and long option exist, empty string otherwise)</li>
         * <li>comma-separated string with long option name(s)</li>
         * <li>first element of the {@link Option#description()} array</li>
         * </ol>
         * <p>Following this, there will be one row for each of the remaining elements of the {@link
         *   Option#description()} array, and these rows look like {@code {"", "", "", "", option.description()[i]}}.</p>
         * <p>If configured, this option renderer adds an additional row to display the default field value.</p>
         * @return a new default OptionRenderer
         */
        public IOptionRenderer createDefaultOptionRenderer() {
            DefaultOptionRenderer result = new DefaultOptionRenderer();
            result.requiredMarker = String.valueOf(requiredOptionMarker);
            if (showDefaultValues != null && showDefaultValues.booleanValue()) {
                result.command = this.command;
            }
            return result;
        }
        /** Returns a new minimal OptionRenderer which converts {@link Option Options} to a single row with two columns
         * of text: an option name and a description. If multiple names or descriptions exist, the first value is used.
         * @return a new minimal OptionRenderer */
        public static IOptionRenderer createMinimalOptionRenderer() {
            return new MinimalOptionRenderer();
        }

        /** Returns a new default ParameterRenderer which converts {@link Parameters Parameters} to four columns of
         * text to match the default {@linkplain TextTable TextTable} column layout. The first row of values looks like this:
         * <ol>
         * <li>empty string </li>
         * <li>empty string </li>
         * <li>parameter(s) label as rendered by the {@link IParamLabelRenderer}</li>
         * <li>first element of the {@link Parameters#description()} array</li>
         * </ol>
         * <p>Following this, there will be one row for each of the remaining elements of the {@link
         *   Parameters#description()} array, and these rows look like {@code {"", "", "", param.description()[i]}}.</p>
         * <p>If configured, this parameter renderer adds an additional row to display the default field value.</p>
         * @return a new default ParameterRenderer
         */
        public IParameterRenderer createDefaultParameterRenderer() {
            DefaultParameterRenderer result = new DefaultParameterRenderer();
            result.requiredMarker = String.valueOf(requiredOptionMarker);
            return result;
        }
        /** Returns a new minimal ParameterRenderer which converts {@link Parameters Parameters} to a single row with
         * two columns of text: an option name and a description. If multiple descriptions exist, the first value is used.
         * @return a new minimal ParameterRenderer */
        public static IParameterRenderer createMinimalParameterRenderer() {
            return new MinimalParameterRenderer();
        }

        /** Returns a value renderer that returns the {@code paramLabel} if defined or the field name otherwise.
         * @return a new minimal ParamLabelRenderer */
        public static IParamLabelRenderer createMinimalParamLabelRenderer() {
            return new IParamLabelRenderer() {
                public Text renderParameterLabel(Field field, Ansi ansi, List<IStyle> styles) {
                    String paramLabel = null;
                    Parameters parameters = field.getAnnotation(Parameters.class);
                    if (parameters != null) {
                        paramLabel = parameters.paramLabel();
                    } else {
                        paramLabel = field.isAnnotationPresent(Option.class) ? field.getAnnotation(Option.class).paramLabel() : null;
                    }
                    String text = paramLabel == null || paramLabel.length() == 0 ? field.getName() : paramLabel;
                    return ansi.apply(text, styles);
                }
                public String separator() { return ""; }
            };
        }
        /** Returns a new default value renderer that separates option parameters from their {@linkplain Option
         * options} with the specified separator string, surrounds optional parameters with {@code '['} and {@code ']'}
         * characters and uses ellipses ("...") to indicate that any number of a parameter are allowed.
         * @return a new default ParamLabelRenderer
         */
        public IParamLabelRenderer createDefaultParamLabelRenderer() {
            return new DefaultParamLabelRenderer(separator);
        }
        /** Sorts Fields annotated with {@code Option} by their option name in case-insensitive alphabetic order. If an
         * Option has multiple names, the shortest name is used for the sorting. Help options follow non-help options.
         * @return a comparator that sorts fields by their option name in case-insensitive alphabetic order */
        public static Comparator<Field> createShortOptionNameComparator() {
            return new SortByShortestOptionNameAlphabetically();
        }
        /** Sorts Fields annotated with {@code Option} by their option {@linkplain Range#max max arity} first, by
         * {@linkplain Range#min min arity} next, and by {@linkplain #createShortOptionNameComparator() option name} last.
         * @return a comparator that sorts fields by arity first, then their option name */
        public static Comparator<Field> createShortOptionArityAndNameComparator() {
            return new SortByOptionArityAndNameAlphabetically();
        }
        /** Sorts short strings before longer strings.
         * @return a comparators that sorts short strings before longer strings */
        public static Comparator<String> shortestFirst() {
            return new ShortestFirst();
        }

        /** Returns whether ANSI escape codes are enabled or not.
         * @return whether ANSI escape codes are enabled or not
         */
        public Ansi ansi() {
            return colorScheme.ansi;
        }

        /** When customizing online help for {@link Option Option} details, a custom {@code IOptionRenderer} can be
         * used to create textual representation of an Option in a tabular format: one or more rows, each containing
         * one or more columns. The {@link Layout Layout} is responsible for placing these text values in the
         * {@link TextTable TextTable}. */
        public interface IOptionRenderer {
            /**
             * Returns a text representation of the specified Option and the Field that captures the option value.
             * @param option the command line option to show online usage help for
             * @param field the field that will hold the value for the command line option
             * @param parameterLabelRenderer responsible for rendering option parameters to text
             * @param scheme color scheme for applying ansi color styles to options and option parameters
             * @return a 2-dimensional array of text values: one or more rows, each containing one or more columns
             */
            Text[][] render(Option option, Field field, IParamLabelRenderer parameterLabelRenderer, ColorScheme scheme);
        }
        /** The DefaultOptionRenderer converts {@link Option Options} to five columns of text to match the default
         * {@linkplain TextTable TextTable} column layout. The first row of values looks like this:
         * <ol>
         * <li>the required option marker (if the option is required)</li>
         * <li>2-character short option name (or empty string if no short option exists)</li>
         * <li>comma separator (only if both short option and long option exist, empty string otherwise)</li>
         * <li>comma-separated string with long option name(s)</li>
         * <li>first element of the {@link Option#description()} array</li>
         * </ol>
         * <p>Following this, there will be one row for each of the remaining elements of the {@link
         *   Option#description()} array, and these rows look like {@code {"", "", "", option.description()[i]}}.</p>
         */
        static class DefaultOptionRenderer implements IOptionRenderer {
            public String requiredMarker = " ";
            public Object command;
            public Text[][] render(Option option, Field field, IParamLabelRenderer paramLabelRenderer, ColorScheme scheme) {
                String[] names = ShortestFirst.sort(option.names());
                int shortOptionCount = names[0].length() == 2 ? 1 : 0;
                String shortOption = shortOptionCount > 0 ? names[0] : "";
                Text paramLabelText = paramLabelRenderer.renderParameterLabel(field, scheme.ansi(), scheme.optionParamStyles);
                String longOption = join(names, shortOptionCount, names.length - shortOptionCount, ", ");
                String sep = shortOptionCount > 0 && names.length > 1 ? "," : "";

                // if no long option, fill in the space between the short option name and the param label value
                if (paramLabelText.length > 0 && longOption.length() == 0) {
                    sep = paramLabelRenderer.separator();
                    paramLabelText = paramLabelText.substring(sep.length());
                }
                Text longOptionText = scheme.optionText(longOption);
                longOptionText = longOptionText.append(paramLabelText);
                String requiredOption = option.required() ? requiredMarker : "";

                boolean showDefault = command != null && !option.help() && !isBoolean(field.getType());
                Object defaultValue = null;
                try {
                    defaultValue = field.get(command);
                    if (defaultValue != null && field.getType().isArray()) {
                        StringBuilder sb = new StringBuilder();
                        for (int i = 0; i < Array.getLength(defaultValue); i++) {
                            sb.append(i > 0 ? ", " : "").append(Array.get(defaultValue, i));
                        }
                        defaultValue = sb.insert(0, "[").append("]").toString();
                    }
                } catch (Exception ex) {
                    showDefault = false;
                }
                final int descriptionCount = Math.max(1, option.description().length);
                final int ROW_COUNT = showDefault ? descriptionCount + 1 : descriptionCount;
                final int COLUMN_COUNT = 5;
                Text EMPTY = Ansi.EMPTY_TEXT;
                Text[][] result = new Text[ROW_COUNT][COLUMN_COUNT];
                result[0] = new Text[] { scheme.optionText(requiredOption), scheme.optionText(shortOption),
                        scheme.ansi().new Text(sep), longOptionText, scheme.ansi().new Text(str(option.description(), 0)) };
                for (int i = 1; i < option.description().length; i++) {
                    result[i] = new Text[] { EMPTY, EMPTY, EMPTY, EMPTY, scheme.ansi().new Text(option.description()[i]) };
                }
                if (showDefault) {
                    Arrays.fill(result[result.length - 1], EMPTY);
                    int row = empty(result[ROW_COUNT - 2][COLUMN_COUNT - 1]) ? ROW_COUNT - 2 : ROW_COUNT - 1;
                    result[row][COLUMN_COUNT - 1] = scheme.ansi().new Text("  Default: " + defaultValue);
                }
                return result;
            }
        }
        /** The MinimalOptionRenderer converts {@link Option Options} to a single row with two columns of text: an
         * option name and a description. If multiple names or description lines exist, the first value is used. */
        static class MinimalOptionRenderer implements IOptionRenderer {
            public Text[][] render(Option option, Field field, IParamLabelRenderer parameterLabelRenderer, ColorScheme scheme) {
                Text optionText = scheme.optionText(option.names()[0]);
                Text paramLabelText = parameterLabelRenderer.renderParameterLabel(field, scheme.ansi(), scheme.optionParamStyles);
                optionText = optionText.append(paramLabelText);
                return new Text[][] {{ optionText,
                                        scheme.ansi().new Text(option.description().length == 0 ? "" : option.description()[0]) }};
            }
        }
        /** The MinimalParameterRenderer converts {@link Parameters Parameters} to a single row with two columns of
         * text: the parameters label and a description. If multiple description lines exist, the first value is used. */
        static class MinimalParameterRenderer implements IParameterRenderer {
            public Text[][] render(Parameters param, Field field, IParamLabelRenderer parameterLabelRenderer, ColorScheme scheme) {
                return new Text[][] {{ parameterLabelRenderer.renderParameterLabel(field, scheme.ansi(), scheme.parameterStyles),
                        scheme.ansi().new Text(param.description().length == 0 ? "" : param.description()[0]) }};
            }
        }
        /** When customizing online help for {@link Parameters Parameters} details, a custom {@code IParameterRenderer}
         * can be used to create textual representation of a Parameters field in a tabular format: one or more rows,
         * each containing one or more columns. The {@link Layout Layout} is responsible for placing these text
         * values in the {@link TextTable TextTable}. */
        public interface IParameterRenderer {
            /**
             * Returns a text representation of the specified Parameters and the Field that captures the parameter values.
             * @param parameters the command line parameters to show online usage help for
             * @param field the field that will hold the value for the command line parameters
             * @param parameterLabelRenderer responsible for rendering parameter labels to text
             * @param scheme color scheme for applying ansi color styles to positional parameters
             * @return a 2-dimensional array of text values: one or more rows, each containing one or more columns
             */
            Text[][] render(Parameters parameters, Field field, IParamLabelRenderer parameterLabelRenderer, ColorScheme scheme);
        }
        /** The DefaultParameterRenderer converts {@link Parameters Parameters} to five columns of text to match the
         * default {@linkplain TextTable TextTable} column layout. The first row of values looks like this:
         * <ol>
         * <li>the required option marker (if the parameter's arity is to have at least one value)</li>
         * <li>empty string </li>
         * <li>empty string </li>
         * <li>parameter(s) label as rendered by the {@link IParamLabelRenderer}</li>
         * <li>first element of the {@link Parameters#description()} array</li>
         * </ol>
         * <p>Following this, there will be one row for each of the remaining elements of the {@link
         *   Parameters#description()} array, and these rows look like {@code {"", "", "", param.description()[i]}}.</p>
         */
        static class DefaultParameterRenderer implements IParameterRenderer {
            public String requiredMarker = " ";
            public Text[][] render(Parameters params, Field field, IParamLabelRenderer paramLabelRenderer, ColorScheme scheme) {
                Text label = paramLabelRenderer.renderParameterLabel(field, scheme.ansi(), scheme.parameterStyles);
                Text requiredParameter = scheme.parameterText(Range.parameterArity(field).min > 0 ? requiredMarker : "");

                final int COLUMN_COUNT = 5;
                final Text EMPTY = Ansi.EMPTY_TEXT;
                Text[][] result = new Text[Math.max(1, params.description().length)][COLUMN_COUNT];
                result[0] = new Text[] { requiredParameter, EMPTY, EMPTY, label, scheme.ansi().new Text(str(params.description(), 0)) };
                for (int i = 1; i < params.description().length; i++) {
                    result[i] = new Text[] { EMPTY, EMPTY, EMPTY, EMPTY, scheme.ansi().new Text(params.description()[i]) };
                }
                return result;
            }
        }
        /** When customizing online usage help for an option parameter or a positional parameter, a custom
         * {@code IParamLabelRenderer} can be used to render the parameter name or label to a String. */
        public interface IParamLabelRenderer {

            /** Returns a text rendering of the Option parameter or positional parameter; returns an empty string
             * {@code ""} if the option is a boolean and does not take a parameter.
             * @param field the annotated field with a parameter label
             * @param ansi determines whether ANSI escape codes should be emitted or not
             * @param styles the styles to apply to the parameter label
             * @return a text rendering of the Option parameter or positional parameter */
            Text renderParameterLabel(Field field, Ansi ansi, List<IStyle> styles);

            /** Returns the separator between option name and param label.
             * @return the separator between option name and param label */
            String separator();
        }
        /**
         * DefaultParamLabelRenderer separates option parameters from their {@linkplain Option options} with a
         * {@linkplain DefaultParamLabelRenderer#separator separator} string, surrounds optional values
         * with {@code '['} and {@code ']'} characters and uses ellipses ("...") to indicate that any number of
         * values is allowed for options or parameters with variable arity.
         */
        static class DefaultParamLabelRenderer implements IParamLabelRenderer {
            /** The string to use to separate option parameters from their options. */
            public final String separator;
            /** Constructs a new DefaultParamLabelRenderer with the specified separator string. */
            public DefaultParamLabelRenderer(String separator) {
                this.separator = Assert.notNull(separator, "separator");
            }
            public String separator() { return separator; }
            public Text renderParameterLabel(Field field, Ansi ansi, List<IStyle> styles) {
                boolean isOptionParameter = field.isAnnotationPresent(Option.class);
                Range arity = isOptionParameter ? Range.optionArity(field) : Range.parameterArity(field);
                Text result = ansi.new Text("");
                String sep = isOptionParameter ? separator : "";
                if (arity.min > 0) {
                    for (int i = 0; i < arity.min; i++) {
                        result = result.append(sep).append(ansi.apply(renderParameterName(field), styles));
                        sep = " ";
                    }
                }
                if (arity.max > arity.min) {
                    sep = result.length == 0 ? (isOptionParameter ? separator : "") : " ";
                    int max = arity.isVariable ? 1 : arity.max - arity.min;
                    for (int i = 0; i < max; i++) {
                        if (sep.trim().length() == 0) {
                            result = result.append(sep + "[").append(ansi.apply(renderParameterName(field), styles));
                        } else {
                            result = result.append("[" + sep).append(ansi.apply(renderParameterName(field), styles));
                        }
                        sep  = " ";
                    }
                    if (arity.isVariable) {
                        result = result.append("...");
                    }
                    for (int i = 0; i < max; i++) { result = result.append("]"); }
                }
                return result;
            }
            private String renderParameterName(Field field) {
                String result = null;
                if (field.isAnnotationPresent(Option.class)) {
                    result = field.getAnnotation(Option.class).paramLabel();
                } else if (field.isAnnotationPresent(Parameters.class)) {
                    result = field.getAnnotation(Parameters.class).paramLabel();
                }
                if (result != null && result.trim().length() > 0) {
                    return result.trim();
                }
                return "<" + field.getName() + ">";
            }
        }
        /** Use a Layout to format usage help text for options and parameters in tabular format.
         * <p>Delegates to the renderers to create {@link Text} values for the annotated fields, and uses a
         * {@link TextTable} to display these values in tabular format. Layout is responsible for deciding which values
         * to display where in the table. By default, Layout shows one option or parameter per table row.</p>
         * <p>Customize by overriding the {@link #layout(Field, CommandLine.Help.Ansi.Text[][])} method.</p>
         * @see IOptionRenderer rendering options to text
         * @see IParameterRenderer rendering parameters to text
         * @see TextTable showing values in a tabular format
         */
        public static class Layout {
            protected final ColorScheme colorScheme;
            protected final TextTable table;
            protected IOptionRenderer optionRenderer;
            protected IParameterRenderer parameterRenderer;

            /** Constructs a Layout with the specified color scheme, a new default TextTable, the
             * {@linkplain Help#createDefaultOptionRenderer() default option renderer}, and the
             * {@linkplain Help#createDefaultParameterRenderer() default parameter renderer}.
             * @param colorScheme the color scheme to use for common, auto-generated parts of the usage help message */
            public Layout(ColorScheme colorScheme) { this(colorScheme, new TextTable(colorScheme.ansi())); }

            /** Constructs a Layout with the specified color scheme, the specified TextTable, the
             * {@linkplain Help#createDefaultOptionRenderer() default option renderer}, and the
             * {@linkplain Help#createDefaultParameterRenderer() default parameter renderer}.
             * @param colorScheme the color scheme to use for common, auto-generated parts of the usage help message
             * @param textTable the TextTable to lay out parts of the usage help message in tabular format */
            public Layout(ColorScheme colorScheme, TextTable textTable) {
                this(colorScheme, textTable, new DefaultOptionRenderer(), new DefaultParameterRenderer());
            }
            /** Constructs a Layout with the specified color scheme, the specified TextTable, the
             * specified option renderer and the specified parameter renderer.
             * @param colorScheme the color scheme to use for common, auto-generated parts of the usage help message
             * @param optionRenderer the object responsible for rendering Options to Text
             * @param parameterRenderer the object responsible for rendering Parameters to Text
             * @param textTable the TextTable to lay out parts of the usage help message in tabular format */
            public Layout(ColorScheme colorScheme, TextTable textTable, IOptionRenderer optionRenderer, IParameterRenderer parameterRenderer) {
                this.colorScheme       = Assert.notNull(colorScheme, "colorScheme");
                this.table             = Assert.notNull(textTable, "textTable");
                this.optionRenderer    = Assert.notNull(optionRenderer, "optionRenderer");
                this.parameterRenderer = Assert.notNull(parameterRenderer, "parameterRenderer");
            }
            /**
             * Copies the specified text values into the correct cells in the {@link TextTable}. This implementation
             * delegates to {@link TextTable#addRowValues(CommandLine.Help.Ansi.Text...)} for each row of values.
             * <p>Subclasses may override.</p>
             * @param field the field annotated with the specified Option or Parameters
             * @param cellValues the text values representing the Option/Parameters, to be displayed in tabular form
             */
            public void layout(Field field, Text[][] cellValues) {
                for (Text[] oneRow : cellValues) {
                    table.addRowValues(oneRow);
                }
            }
            /** Calls {@link #addOption(Field, CommandLine.Help.IParamLabelRenderer)} for all non-hidden Options in the list.
             * @param fields fields annotated with {@link Option} to add usage descriptions for
             * @param paramLabelRenderer object that knows how to render option parameters */
            public void addOptions(List<Field> fields, IParamLabelRenderer paramLabelRenderer) {
                for (Field field : fields) {
                    Option option = field.getAnnotation(Option.class);
                    if (!option.hidden()) {
                        addOption(field, paramLabelRenderer);
                    }
                }
            }
            /**
             * Delegates to the {@link #optionRenderer option renderer} of this layout to obtain
             * text values for the specified {@link Option}, and then calls the {@link #layout(Field, CommandLine.Help.Ansi.Text[][])}
             * method to write these text values into the correct cells in the TextTable.
             * @param field the field annotated with the specified Option
             * @param paramLabelRenderer knows how to render option parameters
             */
            public void addOption(Field field, IParamLabelRenderer paramLabelRenderer) {
                Option option = field.getAnnotation(Option.class);
                Text[][] values = optionRenderer.render(option, field, paramLabelRenderer, colorScheme);
                layout(field, values);
            }
            /** Calls {@link #addPositionalParameter(Field, CommandLine.Help.IParamLabelRenderer)} for all non-hidden Parameters in the list.
             * @param fields fields annotated with {@link Parameters} to add usage descriptions for
             * @param paramLabelRenderer knows how to render option parameters */
            public void addPositionalParameters(List<Field> fields, IParamLabelRenderer paramLabelRenderer) {
                for (Field field : fields) {
                    Parameters parameters = field.getAnnotation(Parameters.class);
                    if (!parameters.hidden()) {
                        addPositionalParameter(field, paramLabelRenderer);
                    }
                }
            }
            /**
             * Delegates to the {@link #parameterRenderer parameter renderer} of this layout
             * to obtain text values for the specified {@link Parameters}, and then calls
             * {@link #layout(Field, CommandLine.Help.Ansi.Text[][])} to write these text values into the correct cells in the TextTable.
             * @param field the field annotated with the specified Parameters
             * @param paramLabelRenderer knows how to render option parameters
             */
            public void addPositionalParameter(Field field, IParamLabelRenderer paramLabelRenderer) {
                Parameters option = field.getAnnotation(Parameters.class);
                Text[][] values = parameterRenderer.render(option, field, paramLabelRenderer, colorScheme);
                layout(field, values);
            }
            /** Returns the section of the usage help message accumulated in the TextTable owned by this layout. */
            @Override public String toString() {
                return table.toString();
            }
        }
        /** Sorts short strings before longer strings. */
        static class ShortestFirst implements Comparator<String> {
            public int compare(String o1, String o2) {
                return o1.length() - o2.length();
            }
            /** Sorts the specified array of Strings shortest-first and returns it. */
            public static String[] sort(String[] names) {
                Arrays.sort(names, new ShortestFirst());
                return names;
            }
        }
        /** Sorts {@code Option} instances by their name in case-insensitive alphabetic order. If an Option has
         * multiple names, the shortest name is used for the sorting. Help options follow non-help options. */
        static class SortByShortestOptionNameAlphabetically implements Comparator<Field> {
            public int compare(Field f1, Field f2) {
                Option o1 = f1.getAnnotation(Option.class);
                Option o2 = f2.getAnnotation(Option.class);
                if (o1 == null) { return 1; } else if (o2 == null) { return -1; } // options before params
                String[] names1 = ShortestFirst.sort(o1.names());
                String[] names2 = ShortestFirst.sort(o2.names());
                int result = names1[0].toUpperCase().compareTo(names2[0].toUpperCase()); // case insensitive sort
                result = result == 0 ? -names1[0].compareTo(names2[0]) : result; // lower case before upper case
                return o1.help() == o2.help() ? result : o2.help() ? -1 : 1; // help options come last
            }
        }
        /** Sorts {@code Option} instances by their max arity first, then their min arity, then delegates to super class. */
        static class SortByOptionArityAndNameAlphabetically extends SortByShortestOptionNameAlphabetically {
            public int compare(Field f1, Field f2) {
                Option o1 = f1.getAnnotation(Option.class);
                Option o2 = f2.getAnnotation(Option.class);
                Range arity1 = Range.optionArity(f1);
                Range arity2 = Range.optionArity(f2);
                int result = arity1.max - arity2.max;
                if (result == 0) {
                    result = arity1.min - arity2.min;
                }
                return result == 0 ? super.compare(f1, f2) : result;
            }
        }
        /**
         * <p>Responsible for spacing out {@link Text} values according to the {@link Column} definitions the table was
         * created with. Columns have a width, indentation, and an overflow policy that decides what to do if a value is
         * longer than the column's width.</p>
         */
        public static class TextTable {
            /** The column definitions of this table. */
            public final Column[] columns;

            /** The {@code char[]} slots of the {@code TextTable} to copy text values into. */
            protected final List<Text> columnValues = new ArrayList<Text>();

            /** By default, indent wrapped lines by 2 spaces. */
            public int indentWrappedLines = 2;

            private final Ansi ansi;

            /** Constructs a TextTable with five columns as follows:
             * <ol>
             * <li>required option/parameter marker (width: 2, indent: 0, TRUNCATE on overflow)</li>
             * <li>short option name (width: 2, indent: 0, TRUNCATE on overflow)</li>
             * <li>comma separator (width: 1, indent: 0, TRUNCATE on overflow)</li>
             * <li>long option name(s) (width: 24, indent: 1, SPAN multiple columns on overflow)</li>
             * <li>description line(s) (width: 51, indent: 1, WRAP to next row on overflow)</li>
             * </ol>
             * @param ansi whether to emit ANSI escape codes or not
             */
            public TextTable(Ansi ansi) {
                // "* -c, --create                Creates a ...."
                this(ansi, new Column[] {
                            new Column(2,                                        0, TRUNCATE), // "*"
                            new Column(2,                                        0, TRUNCATE), // "-c"
                            new Column(1,                                        0, TRUNCATE), // ","
                            new Column(optionsColumnWidth - 2 - 2 - 1       , 1, SPAN),  // " --create"
                            new Column(usageHelpWidth - optionsColumnWidth, 1, WRAP) // " Creates a ..."
                    });
            }

            /** Constructs a new TextTable with columns with the specified width, all SPANning  multiple columns on
             * overflow except the last column which WRAPS to the next row.
             * @param ansi whether to emit ANSI escape codes or not
             * @param columnWidths the width of the table columns (all columns have zero indent)
             */
            public TextTable(Ansi ansi, int... columnWidths) {
                this.ansi = Assert.notNull(ansi, "ansi");
                columns = new Column[columnWidths.length];
                for (int i = 0; i < columnWidths.length; i++) {
                    columns[i] = new Column(columnWidths[i], 0, i == columnWidths.length - 1 ? SPAN: WRAP);
                }
            }
            /** Constructs a {@code TextTable} with the specified columns.
             * @param ansi whether to emit ANSI escape codes or not
             * @param columns columns to construct this TextTable with */
            public TextTable(Ansi ansi, Column... columns) {
                this.ansi = Assert.notNull(ansi, "ansi");
                this.columns = Assert.notNull(columns, "columns");
                if (columns.length == 0) { throw new IllegalArgumentException("At least one column is required"); }
            }
            /** Returns the {@code Text} slot at the specified row and column to write a text value into.
             * @param row the row of the cell whose Text to return
             * @param col the column of the cell whose Text to return
             * @return the Text object at the specified row and column */
            public Text cellAt(int row, int col) { return columnValues.get(col + (row * columns.length)); }

            /** Returns the current number of rows of this {@code TextTable}.
             * @return the current number of rows in this TextTable */
            public int rowCount() { return columnValues.size() / columns.length; }

            /** Adds the required {@code char[]} slots for a new row to the {@link #columnValues} field. */
            public void addEmptyRow() {
                for (int i = 0; i < columns.length; i++) {
                    columnValues.add(ansi.new Text(columns[i].width));
                }
            }

            /** Delegates to {@link #addRowValues(CommandLine.Help.Ansi.Text...)}.
             * @param values the text values to display in each column of the current row */
            public void addRowValues(String... values) {
                Text[] array = new Text[values.length];
                for (int i = 0; i < array.length; i++) {
                    array[i] = values[i] == null ? Ansi.EMPTY_TEXT : ansi.new Text(values[i]);
                }
                addRowValues(array);
            }
            /**
             * Adds a new {@linkplain TextTable#addEmptyRow() empty row}, then calls {@link
             * TextTable#putValue(int, int, CommandLine.Help.Ansi.Text) putValue} for each of the specified values, adding more empty rows
             * if the return value indicates that the value spanned multiple columns or was wrapped to multiple rows.
             * @param values the values to write into a new row in this TextTable
             * @throws IllegalArgumentException if the number of values exceeds the number of Columns in this table
             */
            public void addRowValues(Text... values) {
                if (values.length > columns.length) {
                    throw new IllegalArgumentException(values.length + " values don't fit in " +
                            columns.length + " columns");
                }
                addEmptyRow();
                for (int col = 0; col < values.length; col++) {
                    int row = rowCount() - 1;// write to last row: previous value may have wrapped to next row
                    Point cell = putValue(row, col, values[col]);

                    // add row if a value spanned/wrapped and there are still remaining values
                    if ((cell.y != row || cell.x != col) && col != values.length - 1) {
                        addEmptyRow();
                    }
                }
            }
            /**
             * Writes the specified value into the cell at the specified row and column and returns the last row and
             * column written to. Depending on the Column's {@link Column#overflow Overflow} policy, the value may span
             * multiple columns or wrap to multiple rows when larger than the column width.
             * @param row the target row in the table
             * @param col the target column in the table to write to
             * @param value the value to write
             * @return a Point whose {@code x} value is the last column written to and whose {@code y} value is the
             *          last row written to
             * @throws IllegalArgumentException if the specified row exceeds the table's {@linkplain
             *          TextTable#rowCount() row count}
             */
            public Point putValue(int row, int col, Text value) {
                if (row > rowCount() - 1) {
                    throw new IllegalArgumentException("Cannot write to row " + row + ": rowCount=" + rowCount());
                }
                if (value == null || value.plain.length() == 0) { return new Point(col, row); }
                Column column = columns[col];
                int indent = column.indent;
                switch (column.overflow) {
                    case TRUNCATE:
                        copy(value, cellAt(row, col), indent);
                        return new Point(col, row);
                    case SPAN:
                        int startColumn = col;
                        do {
                            boolean lastColumn = col == columns.length - 1;
                            int charsWritten = lastColumn
                                    ? copy(BreakIterator.getLineInstance(), value, cellAt(row, col), indent)
                                    : copy(value, cellAt(row, col), indent);
                            value = value.substring(charsWritten);
                            indent = 0;
                            if (value.length > 0) { // value did not fit in column
                                ++col;                // write remainder of value in next column
                            }
                            if (value.length > 0 && col >= columns.length) { // we filled up all columns on this row
                                addEmptyRow();
                                row++;
                                col = startColumn;
                                indent = column.indent + indentWrappedLines;
                            }
                        } while (value.length > 0);
                        return new Point(col, row);
                    case WRAP:
                        BreakIterator lineBreakIterator = BreakIterator.getLineInstance();
                        do {
                            int charsWritten = copy(lineBreakIterator, value, cellAt(row, col), indent);
                            value = value.substring(charsWritten);
                            indent = column.indent + indentWrappedLines;
                            if (value.length > 0) {  // value did not fit in column
                                ++row;                 // write remainder of value in next row
                                addEmptyRow();
                            }
                        } while (value.length > 0);
                        return new Point(col, row);
                }
                throw new IllegalStateException(column.overflow.toString());
            }
            private static int length(Text str) {
                return str.length; // TODO count some characters as double length
            }
            private char[] spaces(int length) { char[] result = new char[length]; Arrays.fill(result, ' '); return result; }

            private int copy(BreakIterator line, Text text, Text columnValue, int offset) {
                // Deceive the BreakIterator to ensure no line breaks after '-' character
                line.setText(text.plainString().replace("-", "\u00ff"));
                int done = 0;
                for (int start = line.first(), end = line.next(); end != BreakIterator.DONE; start = end, end = line.next()) {
                    Text word = text.substring(start, end); //.replace("\u00ff", "-"); // not needed
                    if (columnValue.maxLength >= offset + done + length(word)) {
                        done += copy(word, columnValue, offset + done); // TODO localized length
                    } else {
                        break;
                    }
                }
                if (done == 0 && length(text) > columnValue.maxLength) {
                    // The value is a single word that is too big to be written to the column. Write as much as we can.
                    done = copy(text, columnValue, offset);
                }
                return done;
            }
            private static int copy(Text value, Text destination, int offset) {
                int length = Math.min(value.length, destination.maxLength - offset);
                value.getStyledChars(value.from, length, destination, offset);
                return length;
            }

            /** Copies the text representation that we built up from the options into the specified StringBuilder.
             * @param text the StringBuilder to write into
             * @return the specified StringBuilder object (to allow method chaining and a more fluid API) */
            public StringBuilder toString(StringBuilder text) {
                int columnCount = this.columns.length;
                StringBuilder row = new StringBuilder(usageHelpWidth);
                for (int i = 0; i < columnValues.size(); i++) {
                    Text column = columnValues.get(i);
                    row.append(column.toString());
                    row.append(new String(spaces(columns[i % columnCount].width - column.length)));
                    if (i % columnCount == columnCount - 1) {
                        int lastChar = row.length() - 1;
                        while (lastChar >= 0 && row.charAt(lastChar) == ' ') {lastChar--;} // rtrim
                        row.setLength(lastChar + 1);
                        text.append(row.toString()).append(System.getProperty("line.separator"));
                        row.setLength(0);
                    }
                }
                //if (Ansi.enabled()) { text.append(Style.reset.off()); }
                return text;
            }
            public String toString() { return toString(new StringBuilder()).toString(); }
        }
        /** Columns define the width, indent (leading number of spaces in a column before the value) and
         * {@linkplain Overflow Overflow} policy of a column in a {@linkplain TextTable TextTable}. */
        public static class Column {

            /** Policy for handling text that is longer than the column width:
             *  span multiple columns, wrap to the next row, or simply truncate the portion that doesn't fit. */
            public enum Overflow { TRUNCATE, SPAN, WRAP }

            /** Column width in characters */
            public final int width;

            /** Indent (number of empty spaces at the start of the column preceding the text value) */
            public final int indent;

            /** Policy that determines how to handle values larger than the column width. */
            public final Overflow overflow;
            public Column(int width, int indent, Overflow overflow) {
                this.width = width;
                this.indent = indent;
                this.overflow = Assert.notNull(overflow, "overflow");
            }
        }

        /** All usage help message are generated with a color scheme that assigns certain styles and colors to common
         * parts of a usage message: the command name, options, positional parameters and option parameters.
         * Users may customize these styles by creating Help with a custom color scheme.
         * <p>Note that these options and styles may not be rendered if ANSI escape codes are not
         * {@linkplain Ansi#enabled() enabled}.</p>
         * @see Help#defaultColorScheme(Ansi)
         */
        public static class ColorScheme {
            public final List<IStyle> commandStyles = new ArrayList<IStyle>();
            public final List<IStyle> optionStyles = new ArrayList<IStyle>();
            public final List<IStyle> parameterStyles = new ArrayList<IStyle>();
            public final List<IStyle> optionParamStyles = new ArrayList<IStyle>();
            private final Ansi ansi;

            /** Constructs a new ColorScheme with {@link Help.Ansi#AUTO}. */
            public ColorScheme() { this(Ansi.AUTO); }

            /** Constructs a new ColorScheme with the specified Ansi enabled mode.
             * @param ansi whether to emit ANSI escape codes or not
             */
            public ColorScheme(Ansi ansi) {this.ansi = Assert.notNull(ansi, "ansi"); }

            /** Adds the specified styles to the registered styles for commands in this color scheme and returns this color scheme.
             * @param styles the styles to add to the registered styles for commands in this color scheme
             * @return this color scheme to enable method chaining for a more fluent API */
            public ColorScheme commands(IStyle... styles)     { return addAll(commandStyles, styles); }
            /** Adds the specified styles to the registered styles for options in this color scheme and returns this color scheme.
             * @param styles the styles to add to registered the styles for options in this color scheme
             * @return this color scheme to enable method chaining for a more fluent API */
            public ColorScheme options(IStyle... styles)      { return addAll(optionStyles, styles);}
            /** Adds the specified styles to the registered styles for positional parameters in this color scheme and returns this color scheme.
             * @param styles the styles to add to registered the styles for parameters in this color scheme
             * @return this color scheme to enable method chaining for a more fluent API */
            public ColorScheme parameters(IStyle... styles)   { return addAll(parameterStyles, styles);}
            /** Adds the specified styles to the registered styles for option parameters in this color scheme and returns this color scheme.
             * @param styles the styles to add to the registered styles for option parameters in this color scheme
             * @return this color scheme to enable method chaining for a more fluent API */
            public ColorScheme optionParams(IStyle... styles) { return addAll(optionParamStyles, styles);}
            /** Returns a Text with all command styles applied to the specified command string.
             * @param command the command string to apply the registered command styles to
             * @return a Text with all command styles applied to the specified command string */
            public Ansi.Text commandText(String command)         { return ansi().apply(command,     commandStyles); }
            /** Returns a Text with all option styles applied to the specified option string.
             * @param option the option string to apply the registered option styles to
             * @return a Text with all option styles applied to the specified option string */
            public Ansi.Text optionText(String option)           { return ansi().apply(option,      optionStyles); }
            /** Returns a Text with all parameter styles applied to the specified parameter string.
             * @param parameter the parameter string to apply the registered parameter styles to
             * @return a Text with all parameter styles applied to the specified parameter string */
            public Ansi.Text parameterText(String parameter)     { return ansi().apply(parameter,   parameterStyles); }
            /** Returns a Text with all optionParam styles applied to the specified optionParam string.
             * @param optionParam the option parameter string to apply the registered option parameter styles to
             * @return a Text with all option parameter styles applied to the specified option parameter string */
            public Ansi.Text optionParamText(String optionParam) { return ansi().apply(optionParam, optionParamStyles); }

            /** Replaces colors and styles in this scheme with ones specified in system properties, and returns this scheme.
             * Supported property names:<ul>
             *     <li>{@code picocli.color.commands}</li>
             *     <li>{@code picocli.color.options}</li>
             *     <li>{@code picocli.color.parameters}</li>
             *     <li>{@code picocli.color.optionParams}</li>
             * </ul><p>Property values can be anything that {@link Help.Ansi.Style#parse(String)} can handle.</p>
             * @return this ColorScheme
             */
            public ColorScheme applySystemProperties() {
                replace(commandStyles,     System.getProperty("picocli.color.commands"));
                replace(optionStyles,      System.getProperty("picocli.color.options"));
                replace(parameterStyles,   System.getProperty("picocli.color.parameters"));
                replace(optionParamStyles, System.getProperty("picocli.color.optionParams"));
                return this;
            }
            private void replace(List<IStyle> styles, String property) {
                if (property != null) {
                    styles.clear();
                    addAll(styles, Style.parse(property));
                }
            }
            private ColorScheme addAll(List<IStyle> styles, IStyle... add) {
                styles.addAll(Arrays.asList(add));
                return this;
            }

            public Ansi ansi() {
                return ansi;
            }
        }

        /** Creates and returns a new {@link ColorScheme} initialized with picocli default values: commands are bold,
         *  options and parameters use a yellow foreground, and option parameters use italic.
         * @param ansi whether the usage help message should contain ANSI escape codes or not
         * @return a new default color scheme
         */
        public static ColorScheme defaultColorScheme(Ansi ansi) {
            return new ColorScheme(ansi)
                    .commands(Style.bold)
                    .options(Style.fg_yellow)
                    .parameters(Style.fg_yellow)
                    .optionParams(Style.italic);
        }

        /** Provides methods and inner classes to support using ANSI escape codes in usage help messages. */
        public enum Ansi {
            /** Only emit ANSI escape codes if the platform supports it and system property {@code "picocli.ansi"}
             * is not set to any value other than {@code "true"} (case insensitive). */
            AUTO,
            /** Forced ON: always emit ANSI escape code regardless of the platform. */
            ON,
            /** Forced OFF: never emit ANSI escape code regardless of the platform. */
            OFF;
            static Text EMPTY_TEXT = OFF.new Text(0);
            static final boolean isWindows  = System.getProperty("os.name").startsWith("Windows");
            static final boolean isXterm    = System.getenv("TERM") != null && System.getenv("TERM").startsWith("xterm");
            static final boolean ISATTY = calcTTY();

            // http://stackoverflow.com/questions/1403772/how-can-i-check-if-a-java-programs-input-output-streams-are-connected-to-a-term
            static final boolean calcTTY() {
                if (isWindows && isXterm) { return true; } // Cygwin uses pseudo-tty and console is always null...
                try { return System.class.getDeclaredMethod("console").invoke(null) != null; }
                catch (Throwable reflectionFailed) { return true; }
            }
            private static boolean ansiPossible() { return ISATTY && (!isWindows || isXterm); }

            /** Returns {@code true} if ANSI escape codes should be emitted, {@code false} otherwise.
             * @return ON: {@code true}, OFF: {@code false}, AUTO: if system property {@code "picocli.ansi"} is
             *      defined then return its boolean value, otherwise return whether the platform supports ANSI escape codes */
            public boolean enabled() {
                if (this == ON)  { return true; }
                if (this == OFF) { return false; }
                return (System.getProperty("picocli.ansi") == null ? ansiPossible() : Boolean.getBoolean("picocli.ansi"));
            }

            /** Defines the interface for an ANSI escape sequence. */
            public interface IStyle {

                /** The Control Sequence Introducer (CSI) escape sequence {@value}. */
                String CSI = "\u001B[";

                /** Returns the ANSI escape code for turning this style on.
                 * @return the ANSI escape code for turning this style on */
                String on();

                /** Returns the ANSI escape code for turning this style off.
                 * @return the ANSI escape code for turning this style off */
                String off();
            }

            /**
             * A set of pre-defined ANSI escape code styles and colors, and a set of convenience methods for parsing
             * text with embedded markup style names, as well as convenience methods for converting
             * styles to strings with embedded escape codes.
             */
            public enum Style implements IStyle {
                reset(0, 0), bold(1, 21), faint(2, 22), italic(3, 23), underline(4, 24), blink(5, 25), reverse(7, 27),
                fg_black(30, 39), fg_red(31, 39), fg_green(32, 39), fg_yellow(33, 39), fg_blue(34, 39), fg_magenta(35, 39), fg_cyan(36, 39), fg_white(37, 39),
                bg_black(40, 49), bg_red(41, 49), bg_green(42, 49), bg_yellow(43, 49), bg_blue(44, 49), bg_magenta(45, 49), bg_cyan(46, 49), bg_white(47, 49),
                ;
                private final int startCode;
                private final int endCode;

                Style(int startCode, int endCode) {this.startCode = startCode; this.endCode = endCode; }
                public String on() { return CSI + startCode + "m"; }
                public String off() { return CSI + endCode + "m"; }

                                /** Returns the concatenated ANSI escape codes for turning all specified styles on.
                 * @param styles the styles to generate ANSI escape codes for
                 * @return the concatenated ANSI escape codes for turning all specified styles on */
                public static String on(IStyle... styles) {
                    StringBuilder result = new StringBuilder();
                    for (IStyle style : styles) {
                        result.append(style.on());
                    }
                    return result.toString();
                }
                                /** Returns the concatenated ANSI escape codes for turning all specified styles off.
                 * @param styles the styles to generate ANSI escape codes for
                 * @return the concatenated ANSI escape codes for turning all specified styles off */
                public static String off(IStyle... styles) {
                    StringBuilder result = new StringBuilder();
                    for (IStyle style : styles) {
                        result.append(style.off());
                    }
                    return result.toString();
                }
                                /** Parses the specified style markup and returns the associated style.
                                 *  The markup may be one of the Style enum value names, or it may be one of the Style enum value
                                 *  names when {@code "fg_"} is prepended, or it may be one of the indexed colors in the 256 color palette.
                 * @param str the case-insensitive style markup to convert, e.g. {@code "blue"} or {@code "fg_blue"},
                 *          or {@code "46"} (indexed color) or {@code "0;5;0"} (RGB components of an indexed color)
                                 * @return the IStyle for the specified converter
                                 */
                public static IStyle fg(String str) {
                    try { return Style.valueOf(str.toLowerCase(ENGLISH)); } catch (Exception ignored) {}
                    try { return Style.valueOf("fg_" + str.toLowerCase(ENGLISH)); } catch (Exception ignored) {}
                    return new Palette256Color(true, str);
                }
                                /** Parses the specified style markup and returns the associated style.
                                 *  The markup may be one of the Style enum value names, or it may be one of the Style enum value
                                 *  names when {@code "bg_"} is prepended, or it may be one of the indexed colors in the 256 color palette.
                                 * @param str the case-insensitive style markup to convert, e.g. {@code "blue"} or {@code "bg_blue"},
                 *          or {@code "46"} (indexed color) or {@code "0;5;0"} (RGB components of an indexed color)
                                 * @return the IStyle for the specified converter
                                 */
                public static IStyle bg(String str) {
                    try { return Style.valueOf(str.toLowerCase(ENGLISH)); } catch (Exception ignored) {}
                    try { return Style.valueOf("bg_" + str.toLowerCase(ENGLISH)); } catch (Exception ignored) {}
                    return new Palette256Color(false, str);
                }
                /** Parses the specified comma-separated sequence of style descriptors and returns the associated
                 *  styles. For each markup, strings starting with {@code "bg("} are delegated to
                 *  {@link #bg(String)}, others are delegated to {@link #bg(String)}.
                 * @param commaSeparatedCodes one or more descriptors, e.g. {@code "bg(blue),underline,red"}
                 * @return an array with all styles for the specified descriptors
                 */
                public static IStyle[] parse(String commaSeparatedCodes) {
                    String[] codes = commaSeparatedCodes.split(",");
                    IStyle[] styles = new IStyle[codes.length];
                    for(int i = 0; i < codes.length; ++i) {
                        if (codes[i].toLowerCase(ENGLISH).startsWith("fg(")) {
                            int end = codes[i].indexOf(')');
                            styles[i] = Style.fg(codes[i].substring(3, end < 0 ? codes[i].length() : end));
                        } else if (codes[i].toLowerCase(ENGLISH).startsWith("bg(")) {
                            int end = codes[i].indexOf(')');
                            styles[i] = Style.bg(codes[i].substring(3, end < 0 ? codes[i].length() : end));
                        } else {
                            styles[i] = Style.fg(codes[i]);
                        }
                    }
                    return styles;
                }
            }

            /** Defines a palette map of 216 colors: 6 * 6 * 6 cube (216 colors):
             * 16 + 36 * r + 6 * g + b (0 &lt;= r, g, b &lt;= 5). */
            static class Palette256Color implements IStyle {
                private final int fgbg;
                private final int color;

                Palette256Color(boolean foreground, String color) {
                    this.fgbg = foreground ? 38 : 48;
                    String[] rgb = color.split(";");
                    if (rgb.length == 3) {
                        this.color = 16 + 36 * Integer.decode(rgb[0]) + 6 * Integer.decode(rgb[1]) + Integer.decode(rgb[2]);
                    } else {
                        this.color = Integer.decode(color);
                    }
                }
                public String on() { return String.format(CSI + "%d;5;%dm", fgbg, color); }
                public String off() { return CSI + (fgbg + 1) + "m"; }
            }
            private static class StyledSection {
                int startIndex, length;
                String startStyles, endStyles;
                StyledSection(int start, int len, String style1, String style2) {
                    startIndex = start; length = len; startStyles = style1; endStyles = style2;
                }
                StyledSection withStartIndex(int newStart) {
                    return new StyledSection(newStart, length, startStyles, endStyles);
                }
            }

            /**
             * Returns a new Text object where all the specified styles are applied to the full length of the
             * specified plain text.
             * @param plainText the string to apply all styles to. Must not contain markup!
             * @param styles the styles to apply to the full plain text
             * @return a new Text object
             */
            public Text apply(String plainText, List<IStyle> styles) {
                if (plainText.length() == 0) { return new Text(0); }
                Text result = new Text(plainText.length());
                IStyle[] all = styles.toArray(new IStyle[styles.size()]);
                result.sections.add(new StyledSection(
                        0, plainText.length(), Style.on(all), Style.off(reverse(all)) + Style.reset.off()));
                result.plain.append(plainText);
                result.length = result.plain.length();
                return result;
            }

            private static <T> T[] reverse(T[] all) {
                for (int i = 0; i < all.length / 2; i++) {
                    T temp = all[i];
                    all[i] = all[all.length - i - 1];
                    all[all.length - i - 1] = temp;
                }
                return all;
            }
            /** Encapsulates rich text with styles and colors. Text objects may be constructed with Strings containing
             * markup like {@code @|bg(red),white,underline some text|@}, and this class converts the markup to ANSI
             * escape codes.
             * <p>
             * Internally keeps both an enriched and a plain text representation to allow layout components to calculate
             * text width while remaining unaware of the embedded ANSI escape codes.</p> */
            public class Text implements Cloneable {
                private final int maxLength;
                private int from;
                private int length;
                private StringBuilder plain = new StringBuilder();
                private List<StyledSection> sections = new ArrayList<StyledSection>();

                /** Constructs a Text with the specified max length (for use in a TextTable Column).
                 * @param maxLength max length of this text */
                public Text(int maxLength) { this.maxLength = maxLength; }

                /**
                 * Constructs a Text with the specified String, which may contain markup like
                 * {@code @|bg(red),white,underline some text|@}.
                 * @param input the string with markup to parse
                 */
                public Text(String input) {
                    maxLength = -1;
                    plain.setLength(0);
                    int i = 0;

                    while (true) {
                        int j = input.indexOf("@|", i);
                        if (j == -1) {
                            if (i == 0) {
                                plain.append(input);
                                length = plain.length();
                                return;
                            }
                            plain.append(input.substring(i, input.length()));
                            length = plain.length();
                            return;
                        }
                        plain.append(input.substring(i, j));
                        int k = input.indexOf("|@", j);
                        if (k == -1) {
                            plain.append(input);
                            length = plain.length();
                            return;
                        }

                        j += 2;
                        String spec = input.substring(j, k);
                        String[] items = spec.split(" ", 2);
                        if (items.length == 1) {
                            plain.append(input);
                            length = plain.length();
                            return;
                        }

                        IStyle[] styles = Style.parse(items[0]);
                        addStyledSection(plain.length(), items[1].length(),
                                Style.on(styles), Style.off(reverse(styles)) + Style.reset.off());
                        plain.append(items[1]);
                        i = k + 2;
                    }
                }
                private void addStyledSection(int start, int length, String startStyle, String endStyle) {
                    sections.add(new StyledSection(start, length, startStyle, endStyle));
                }
                public Object clone() {
                    try { return super.clone(); } catch (CloneNotSupportedException e) { throw new IllegalStateException(e); }
                }

                /** Returns a new {@code Text} instance that is a substring of this Text. Does not modify this instance!
                 * @param start index in the plain text where to start the substring
                 * @return a new Text instance that is a substring of this Text */
                public Text substring(int start) {
                    return substring(start, length);
                }

                /** Returns a new {@code Text} instance that is a substring of this Text. Does not modify this instance!
                 * @param start index in the plain text where to start the substring
                 * @param end index in the plain text where to end the substring
                 * @return a new Text instance that is a substring of this Text */
                public Text substring(int start, int end) {
                    Text result = (Text) clone();
                    result.from = from + start;
                    result.length = end - start;
                    return result;
                }
                /** Returns a new {@code Text} instance with the specified text appended. Does not modify this instance!
                 * @param string the text to append
                 * @return a new Text instance */
                public Text append(String string) {
                    return append(new Text(string));
                }

                /** Returns a new {@code Text} instance with the specified text appended. Does not modify this instance!
                 * @param other the text to append
                 * @return a new Text instance */
                public Text append(Text other) {
                    Text result = (Text) clone();
                    result.plain = new StringBuilder(plain.toString().substring(from, from + length));
                    result.from = 0;
                    result.sections = new ArrayList<StyledSection>();
                    for (StyledSection section : sections) {
                        result.sections.add(section.withStartIndex(section.startIndex - from));
                    }
                    result.plain.append(other.plain.toString().substring(other.from, other.from + other.length));
                    for (StyledSection section : other.sections) {
                        int index = result.length + section.startIndex - other.from;
                        result.sections.add(section.withStartIndex(index));
                    }
                    result.length = result.plain.length();
                    return result;
                }

                /**
                 * Copies the specified substring of this Text into the specified destination, preserving the markup.
                 * @param from start of the substring
                 * @param length length of the substring
                 * @param destination destination Text to modify
                 * @param offset indentation (padding)
                 */
                public void getStyledChars(int from, int length, Text destination, int offset) {
                    if (destination.length < offset) {
                        for (int i = destination.length; i < offset; i++) {
                            destination.plain.append(' ');
                        }
                        destination.length = offset;
                    }
                    for (StyledSection section : sections) {
                        destination.sections.add(section.withStartIndex(section.startIndex - from + destination.length));
                    }
                    destination.plain.append(plain.toString().substring(from, from + length));
                    destination.length = destination.plain.length();
                }
                /** Returns the plain text without any formatting.
                 * @return the plain text without any formatting */
                public String plainString() {  return plain.toString().substring(from, from + length); }

                public boolean equals(Object obj) { return toString().equals(String.valueOf(obj)); }
                public int hashCode() { return toString().hashCode(); }

                /** Returns a String representation of the text with ANSI escape codes embedded, unless ANSI is
                 * {@linkplain Ansi#enabled()} not enabled}, in which case the plain text is returned.
                 * @return a String representation of the text with ANSI escape codes embedded (if enabled) */
                public String toString() {
                    if (!Ansi.this.enabled()) {
                        return plain.toString().substring(from, from + length);
                    }
                    if (length == 0) { return ""; }
                    StringBuilder sb = new StringBuilder(plain.length() + 20 * sections.size());
                    StyledSection current = null;
                    int end = Math.min(from + length, plain.length());
                    for (int i = from; i < end; i++) {
                        StyledSection section = findSectionContaining(i);
                        if (section != current) {
                            if (current != null) { sb.append(current.endStyles); }
                            if (section != null) { sb.append(section.startStyles); }
                            current = section;
                        }
                        sb.append(plain.charAt(i));
                    }
                    if (current != null) { sb.append(current.endStyles); }
                    return sb.toString();
                }

                private StyledSection findSectionContaining(int index) {
                    for (StyledSection section : sections) {
                        if (index >= section.startIndex && index < section.startIndex + section.length) {
                            return section;
                        }
                    }
                    return null;
                }
            }
        }
    }

    /**
     * Utility class providing some defensive coding convenience methods.
     */
    private static final class Assert {
        /**
         * Throws a NullPointerException if the specified object is null.
         * @param object the object to verify
         * @param description error message
         * @param <T> type of the object to check
         * @return the verified object
         */
        static <T> T notNull(T object, String description) {
            if (object == null) {
                throw new NullPointerException(description);
            }
            return object;
        }
        private Assert() {} // private constructor: never instantiate
    }
    private enum TraceLevel { OFF, WARN, INFO, DEBUG;
        public boolean isEnabled(TraceLevel other) { return ordinal() >= other.ordinal(); }
        private void print(Tracer tracer, String msg, Object... params) {
            if (tracer.level.isEnabled(this)) { tracer.stream.printf(prefix(msg), params); }
        }
        private String prefix(String msg) { return "[picocli " + this + "] " + msg; }
        static TraceLevel lookup(String key) { return key == null ? WARN : empty(key) ? INFO : valueOf(key); }
    }
    private static class Tracer {
        TraceLevel level = TraceLevel.lookup(System.getProperty("picocli.trace"));
        PrintStream stream = System.err;
        void warn (String msg, Object... params) { TraceLevel.WARN.print(this, msg, params); }
        void info (String msg, Object... params) { TraceLevel.INFO.print(this, msg, params); }
        void debug(String msg, Object... params) { TraceLevel.DEBUG.print(this, msg, params); }
        boolean isWarn()  { return level.isEnabled(TraceLevel.WARN); }
        boolean isInfo()  { return level.isEnabled(TraceLevel.INFO); }
        boolean isDebug() { return level.isEnabled(TraceLevel.DEBUG); }
    }

    /**
     * Exception indicating something went wrong while parsing command line options.
     */
    public static class ParameterException extends RuntimeException {
        private static final long serialVersionUID = 1477112829129763139L;
        public ParameterException(String msg) {
            super(msg);
        }

        public ParameterException(String msg, Exception ex) {
            super(msg, ex);
        }

        private static ParameterException create(Exception ex, String arg, int i, String[] args) {
            String msg = ex.getClass().getSimpleName() + ": " + ex.getLocalizedMessage()
                    + " while processing argument at or before arg[" + i + "] '" + arg + "' in " + Arrays.toString(args) + ": " + ex.toString();
            return new ParameterException(msg, ex);
        }
    }
    /**
     * Exception indicating that a required parameter was not specified.
     */
    public static class MissingParameterException extends ParameterException {
        private static final long serialVersionUID = 5075678535706338753L;
        public MissingParameterException(String msg) {
            super(msg);
        }

        private static MissingParameterException create(Collection<Field> missing) {
            if (missing.size() == 1) {
                return new MissingParameterException("Missing required option '"
                        + missing.iterator().next().getName() + "'");
            }
            List<String> names = new ArrayList<String>(missing.size());
            for (Field field : missing) {
                names.add(field.getName());
            }
            return new MissingParameterException("Missing required options " + names.toString());
        }
    }

    /**
     * Exception indicating that multiple fields have been annotated with the same Option name.
     */
    public static class DuplicateOptionAnnotationsException extends ParameterException {
        private static final long serialVersionUID = -3355128012575075641L;
        public DuplicateOptionAnnotationsException(String msg) {
            super(msg);
        }

        private static DuplicateOptionAnnotationsException create(String name, Field field1, Field field2) {
            return new DuplicateOptionAnnotationsException("Option name '" + name + "' is used by both " +
                    field1.getDeclaringClass().getName() + "." + field1.getName() + " and " +
                    field2.getDeclaringClass().getName() + "." + field2.getName());
        }
    }
    /** Exception indicating that there was a gap in the indices of the fields annotated with {@link Parameters}. */
    public static class ParameterIndexGapException extends ParameterException {
        private static final long serialVersionUID = -1520981133257618319L;
        public ParameterIndexGapException(String msg) { super(msg); }
    }
    /** Exception indicating that a command line argument could not be mapped to any of the fields annotated with
     * {@link Option} or {@link Parameters}. */
    public static class UnmatchedArgumentException extends ParameterException {
        private static final long serialVersionUID = -8700426380701452440L;
        public UnmatchedArgumentException(String msg) { super(msg); }
        public UnmatchedArgumentException(Stack<String> args) {
            this("Unmatched argument" + (args.size() == 1 ? " " : "s ") + reverse(args));
        }
    }
    /** Exception indicating that more values were specified for an option or parameter than its {@link Option#arity() arity} allows. */
    public static class MaxValuesforFieldExceededException extends ParameterException {
        private static final long serialVersionUID = 6536145439570100641L;
        public MaxValuesforFieldExceededException(String msg) { super(msg); }
    }
    /** Exception indicating that an option for a single-value field has been specified multiple times on the command line. */
    public static class OverwrittenOptionException extends ParameterException {
        private static final long serialVersionUID = 1338029208271055776L;
        public OverwrittenOptionException(String msg) { super(msg); }
    }
    /**
     * Exception indicating that an annotated field had a type for which no {@link ITypeConverter} was
     * {@linkplain #registerConverter(Class, ITypeConverter) registered}.
     */
    public static class MissingTypeConverterException extends ParameterException {
        private static final long serialVersionUID = -6050931703233083760L;
        public MissingTypeConverterException(String msg) {
            super(msg);
        }
    }
}

picocli - a mighty tiny command line interface

1. Introduction

2. Options and Parameters

2.1. Options

2.2. Short Options

2.3. Positional Parameters

2.4. Double dash (--)

3. Strongly Typed Everything

3.1. Built-in Types

3.2. Custom Type Converters

3.3. Arrays, Collections, Maps

3.3.1. Arrays and Collections

3.3.2. Maps

4. Multiple Values

4.1. Default Arity

4.2. Arity

4.3. Split Regex

4.4. Multiple Occurrences

5. Required Arguments

5.1. Required Options

5.2. Required Parameters

6. Help Options

7. Version Help

8. Usage Help

8.1. Compact Example

8.2. Command Name

8.3. Parameter Labels

8.4. Unsorted Option List

8.5. Abbreviated Synopsis

8.6. Custom Synopsis

8.7. Header and Footer

8.8. Section Headings

8.9. Expanded Example

8.10. Option-Parameter Separators

8.11. Hidden Options and Parameters

8.12. Show Default Values

8.13. Required-Option Marker

9. ANSI Colors and Styles

9.1. Colorized Example

9.2. Usage Help with Styles and Colors

9.3. More Colors

9.4. Configuring Fixed Elements

9.4.1. Color Scheme

9.4.2. Color Scheme Overrides

9.5. Supported Platforms

9.5.1. Unix and Linux

9.5.2. Windows

9.6. Forcing ANSI On/Off

10. Usage Help API

10.1. Reordering Sections

10.2. Custom Layout

11. Subcommands

11.1. Registering Subcommands Programmatically

11.2. Registering Subcommands Declaratively

11.3. Parsing Subcommands

11.4. Usage Help for Subcommands

11.5. Nested sub-subcommands

12. Tips & Tricks

12.1. Less Boilerplate

12.2. Boolean Parameters

12.3. Hexadecimal Values

12.4. Option-Parameter Separators

12.4.1. Default Separators

12.4.2. Custom Separators

12.5. Subclassing for Reuse

12.6. Best Practices for Command Line Interfaces

13. Tracing

14. TAB Autocomplete

15. API Javadoc

16. GitHub Project

17. Issue Tracker

18. License

19. Releases

20. Download

20.1. Gradle

20.2. Maven

20.3. Scala SBT

20.4. Ivy

20.5. Source

2.4. Double dash (`--`)