public Class OptionParser

Parses command line arguments, using a syntax that attempts to take from the best of POSIX getopt() and GNU getopt_long().

This parser supports short options and long options.

• Short options begin with a single hyphen ("-") followed by a single letter or digit, or question mark ("?"), or dot ("."), or underscore ("_").
• Short options can accept single arguments. The argument can be made required or optional. The option's argument can occur:
  • in the slot after the option, as in -d /tmp
  • right up against the option, as in -d/tmp
  • right up against the option separated by an equals sign ("="), as in -d=/tmp
  To specify n arguments for an option, specify the option n times, once for each argument, as in -d /tmp -d /var -d /opt; or, when using the "separated values" clause of the "fluent interface" (see below), give multiple values separated by a given character as a single argument to the option.
• Short options can be clustered, so that -abc is treated as -a -b -c. If a short option in the cluster can accept an argument, the remaining characters are interpreted as the argument for that option.
• An argument consisting only of two hyphens ("--") signals that the remaining arguments are to be treated as non-options.
• An argument consisting only of a single hyphen is considered a non-option argument (though it can be an argument of an option). Many Unix programs treat single hyphens as stand-ins for the standard input or standard output streams.
• Long options begin with two hyphens ("--"), followed by multiple letters, digits, hyphens, question marks, or dots. A hyphen cannot be the first character of a long option specification when configuring the parser.
• You can abbreviate long options, so long as the abbreviation is unique. Suppress this behavior if you wish using this constructor.
• Long options can accept single arguments. The argument can be made required or optional. The option's argument can occur:
  • in the slot after the option, as in --directory /tmp
  • right up against the option separated by an equals sign ("="), as in --directory=/tmp
  Specify multiple arguments for a long option in the same manner as for short options (see above).
• You can use a single hyphen ("-") instead of a double hyphen ("--") for a long option.
• The option -W is reserved. If you tell the parser to recognize alternative long options, then it will treat, for example, -W foo=bar as the long option foo with argument bar, as though you had written --foo=bar.
• You can specify -W as a valid short option, or use it as an abbreviation for a long option, but recognizing alternative long options will always supersede this behavior.
• You can specify a given short or long option multiple times on a single command line. The parser collects any arguments specified for those options as a list.
• If the parser detects an option whose argument is optional, and the next argument "looks like" an option, that argument is not treated as the argument to the option, but as a potentially valid option. If, on the other hand, the optional argument is typed as a derivative of Number, then that argument is treated as the negative number argument of the option, even if the parser recognizes the corresponding numeric option. For example:

  
      OptionParser parser = new OptionParser();
      parser.accepts( "a" ).withOptionalArg().ofType( Integer.class );
      parser.accepts( "2" );
      OptionSet options = parser.parse( "-a", "-2" );
    

  In this case, the option set contains "a" with argument -2, not both "a" and "2". Swapping the elements in the args array gives the latter.

There are two ways to tell the parser what options to recognize:

1. A "fluent interface"-style API for specifying options, available since version 2. Sentences in this fluent interface language begin with a call to accepts or acceptsAll methods; calls on the ensuing chain of objects describe whether the options can take an argument, whether the argument is required or optional, to what type arguments of the options should be converted if any, etc. Since version 3, these calls return an instance of OptionSpec, which can subsequently be used to retrieve the arguments of the associated option in a type-safe manner.
2. Since version 1, a more concise way of specifying short options has been to use the special constructor. Arguments of options specified in this manner will be of type String. Here are the rules for the format of the specification strings this constructor accepts:
   • Any letter or digit is treated as an option character.
   • An option character can be immediately followed by an asterisk (*) to indicate that the option is a "help" option.
   • If an option character (with possible trailing asterisk) is followed by a single colon (":"), then the option requires an argument.
   • If an option character (with possible trailing asterisk) is followed by two colons ("::"), then the option accepts an optional argument.
   • Otherwise, the option character accepts no argument.
   • If the option specification string begins with a plus sign ("+" ), the parser will behave "POSIX-ly correct".
   • If the option specification string contains the sequence "W;" (capital W followed by a semicolon), the parser will recognize the alternative form of long options.

Each of the options in a list of options given to acceptsAll is treated as a synonym of the others. For example:

    
    OptionParser parser = new OptionParser();
    parser.acceptsAll( asList( "w", "interactive", "confirmation" ) );
    OptionSet options = parser.parse( "-w" );
    
  

In this case, options.has would answer true when given arguments "w", "interactive", and "confirmation". The OptionSet would give the same responses to these arguments for its other methods as well.

By default, as with GNU getopt(), the parser allows intermixing of options and non-options. If, however, the parser has been created to be "POSIX-ly correct", then the first argument that does not look lexically like an option, and is not a required argument of a preceding option, signals the end of options. You can still bind optional arguments to their options using the abutting (for short options) or = syntax.

Unlike GNU getopt(), this parser does not honor the environment variable POSIXLY_CORRECT. "POSIX-ly correct" parsers are configured by either:

1. using the method posixlyCorrect(boolean), or
2. using the constructor with an argument whose first character is a plus sign ("+")