Parsing arguments to a Java command line program

Question

What if I wanted to parse this   java MyProgram -r opt1 -S opt2 arg1 arg2 arg3 arg4 --test -A opt3   And the result I want in my program is   regular Java args    of size 4 org apache commons cli Options    of size 3 org apache commons cli Options    2 of size 1   I would prefer to use Apache Commons CLI  but the documentation is a little unclear about the case I present above   Specifically  the documentation doesn t tell you how to handle options of the 3rd type I specify below    1  options with a  -  char 2  options with a  --  char 3  options without any marker  or  bare args     I wish that Apache Commons CLI would work but STILL be able to pass regular args to the program if those args didn t have a option prefix   Maybe it does but the documentation doesnt say so as I read through it

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Use the Apache Commons CLI library commandline getArgs   to get arg1  arg2  arg3  and arg4   Here is some code         import org apache commons cli CommandLine      import org apache commons cli Option      import org apache commons cli Options      import org apache commons cli Option Builder      import org apache commons cli CommandLineParser      import org apache commons cli DefaultParser      import org apache commons cli ParseException       public static void main String   parameters                CommandLine commandLine          Option option A   Option builder  A                required true               desc  The A option                longOpt  opt3                build            Option option r   Option builder  r                required true               desc  The r option                longOpt  opt1                build            Option option S   Option builder  S                required true               desc  The S option                longOpt  opt2                build            Option option test   Option builder                required true               desc  The test option                longOpt  test                build            Options options   new Options            CommandLineParser parser   new DefaultParser             String   testArgs              -r    opt1    -S    opt2    arg1    arg2              arg3    arg4    --test    -A    opt3               options addOption option A           options addOption option r           options addOption option S           options addOption option test            try                       commandLine   parser parse options  testArgs                if  commandLine hasOption  A                                  System out print  Option A is present   The value is                      System out println commandLine getOptionValue  A                                if  commandLine hasOption  r                                  System out print  Option r is present   The value is                      System out println commandLine getOptionValue  r                                if  commandLine hasOption  S                                  System out print  Option S is present   The value is                      System out println commandLine getOptionValue  S                                if  commandLine hasOption  test                                  System out println  Option test is present   This is a flag option                                                  String   remainder   commandLine getArgs                    System out print  Remaining arguments                      for  String argument   remainder                                        System out print argument                       System out print                                          System out println                                     catch  ParseException exception                        System out print  Parse error                  System out println exception getMessage

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Here is  DwB solution upgraded to Commons CLI 1 3 1 compliance  replaced deprecated components OptionBuilder and GnuParser   The Apache documentation uses examples that in real life have unmarked bare arguments but ignores them  Thanks  DwB for showing how it works   import org apache commons cli CommandLine  import org apache commons cli CommandLineParser  import org apache commons cli DefaultParser  import org apache commons cli HelpFormatter  import org apache commons cli Option  import org apache commons cli Options  import org apache commons cli ParseException   public static void main String   parameters        CommandLine commandLine      Option option A   Option builder  A   argName  opt3   hasArg   desc  The A option   build        Option option r   Option builder  r   argName  opt1   hasArg   desc  The r option   build        Option option S   Option builder  S   argName  opt2   hasArg   desc  The S option   build        Option option test   Option builder   longOpt  test   desc  The test option   build        Options options   new Options        CommandLineParser parser   new DefaultParser         options addOption option A       options addOption option r       options addOption option S       options addOption option test        String header                     lt arg1 gt    lt arg2 gt    lt arg3 gt      n       Options  flags and arguments may be in any order       String footer    This is DwB s solution brought to Commons CLI 1 3 1 compliance  deprecated methods replaced        HelpFormatter formatter   new HelpFormatter        formatter printHelp  CLIsample   header  options  footer  true            String   testArgs                  -r    opt1    -S    opt2    arg1    arg2                        arg3    arg4    --test    -A    opt3           try               commandLine   parser parse options  testArgs            if  commandLine hasOption  A                          System out print  Option A is present   The value is                  System out println commandLine getOptionValue  A                        if  commandLine hasOption  r                          System out print  Option r is present   The value is                  System out println commandLine getOptionValue  r                        if  commandLine hasOption  S                          System out print  Option S is present   The value is                  System out println commandLine getOptionValue  S                        if  commandLine hasOption  test                          System out println  Option test is present   This is a flag option                                      String   remainder   commandLine getArgs                System out print  Remaining arguments                  for  String argument   remainder                                System out print argument                   System out print                                  System out println                         catch  ParseException exception                System out print  Parse error              System out println exception getMessage                Output   usage  CLIsample  -A  lt opt3 gt    -r  lt opt1 gt    -S  lt opt2 gt    --test                     lt arg1 gt    lt arg2 gt    lt arg3 gt             Options  flags and arguments may be in any order  -A  lt opt3 gt    The A option  -r  lt opt1 gt    The r option  -S  lt opt2 gt    The S option     --test   The test option This is DwB s solution brought to Commons CLI 1 3 1 compliance  deprecated methods replaced  Option A is present   The value is  opt3 Option r is present   The value is  opt1 Option S is present   The value is  opt2 Option test is present   This is a flag option  Remaining arguments  arg1 arg2 arg3 arg4

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You could use https   github com jankroken commandline   here s how to do that   To make this example work  I must make assumptions about what the arguments means - just picking something here     -r opt1   gt  replyAddress opt1 -S opt2 arg1 arg2 arg3 arg4   gt  subjects  opt2 arg1 arg2 arg3 arg4  --test   test true  default false  -A opt3   gt  address opt3   this can then be set up this way   public class MyProgramOptions     private String replyAddress    private String address    private List lt String gt  subjects    private boolean test   false      ShortSwitch  r      LongSwitch  replyAddress      if you also want a long variant  This can be skipped    SingleArgument   public void setReplyAddress String replyAddress        this replyAddress   replyAddress          ShortSwitch  S      AllAvailableArguments   public void setSubjects List lt String gt  subjects        this subjects   subjects          LongSwitch  test      Toggle true    public void setTest boolean test        this test   test          ShortSwitch  A      SingleArgument   public void setAddress String address        this address   address            getters        and then in the main method  you can just do   public final static void main String   args      try       MyProgramOptions options   CommandLineParser parse MyProgramOptions class  args  OptionStyle SIMPLE           and then you can pass options to your application logic         catch

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I realize that the question mentions a preference for Commons CLI  but I guess that when this question was asked  there was not much choice in terms of Java command line parsing libraries  But nine years later  in 2020  would you not rather write code like the below   import picocli CommandLine  import picocli CommandLine Command  import picocli CommandLine Option  import picocli CommandLine Parameters  import java io File  import java util List  import java util concurrent Callable    Command name    myprogram   mixinStandardHelpOptions   true    description    Does something useful    version    1 0   public class MyProgram implements Callable lt Integer gt          Option names    -r   description    The r option   String rValue       Option names    -S   description    The S option   String sValue       Option names    -A   description    The A file   File aFile       Option names    --test   description    The test option   boolean test       Parameters description    Positional params   List lt String gt  positional        Override     public Integer call             System out printf  -r  s n   rValue           System out printf  -S  s n   sValue           System out printf  -A  s n   aFile           System out printf  --test  s n   test           System out printf  positionals  s n   positional           return 0             public static void main String    args            System exit new CommandLine new MyProgram    execute args              Execute by running the command in the question   java MyProgram -r opt1 -S opt2 arg1 arg2 arg3 arg4 --test -A opt3   What I like about this code is that it is    compact - no boilerplate declarative - using annotations instead of a builder API strongly typed - annotated fields can be any type  not just String no duplication - option declaration and getting parse result are together in the annotated field clear - the annotations express the intention better than imperative code separation of concerns - the business logic in the call method is free of parsing-related logic convenient - one line of code in main wires up the parser and runs the business logic in the Callable powerful - automatic usage and version help with the built-in --help and --version options user-friendly - usage help message uses colors to contrast important elements like option names from the rest of the usage help to reduce the cognitive load on the user   The above functionality is only part of what you get when you use the picocli  https   picocli info  library   Now  bear in mind that I am totally  completely  and utterly biased  being the author of picocli   -  But I do believe that in 2020 we have better alternatives for building a command line apps than Commons CLI

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Ok  thanks to Charles Goodwin for the concept    Here is the answer   import java util    public class Test      public static void main String   args         List lt String gt  argsList    new ArrayList lt String gt            List lt String gt  optsList    new ArrayList lt String gt          List lt String gt  doubleOptsList    new ArrayList lt String gt          for  int i 0  i  lt  args length  i               switch  args i  charAt 0              case  -                if  args i  charAt 1      -                      int len   0                   String argstring   args i  toString                     len   argstring length                     System out println  Found double dash with command                          argstring substring 2  len                      doubleOptsList add argstring substring 2  len                              else                    System out println  Found dash with command                         args i  charAt 1      and value     args i 1                         i  i 1                   optsList add args i                                             break                    default                       System out println  Add a default arg               argsList add args i             break

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You could use the refcodes-console artifact at refcodes-console on REFCODES ORG   Option lt String gt  r       new StringOptionImpl   -r   null   opt1            Option lt String gt  s       new StringOptionImpl   -S   null   opt2            Operand lt String gt  arg1   new StringOperandImpl   arg1            Operand lt String gt  arg2   new StringOperandImpl   arg2            Operand lt String gt  arg3   new StringOperandImpl   arg3            Operand lt String gt  arg4   new StringOperandImpl   arg4            Switch test            new SwitchImpl  null   --test            Option lt String gt  a       new StringOptionImpl   -A   null   opt3            Condition theRoot      new AndConditionImpl  r  s  a  arg1  arg2  arg3  arg4      test      Create your arguments parser ArgsParserImpl with your root condition   ArgsParser theArgsParser   new ArgsParserImpl  theRoot    theArgsParser setName   MyProgramm     theArgsParser setSyntaxNotation  SyntaxNotation GNU POSIX      Above you define your syntax  below you invoke the parser   theArgsParser printUsage    theArgsParser printSeparatorLn    theArgsParser printOptions    theArgsParser evalArgs  new String          -r    RRRRR    -S    SSSSS    11111    22222    33333    44444         --test    -A    AAAAA         In case you provided some good descriptions  theArgsParser printUsage   will even show you the pretty printed usage   Usage  MyProgramm -r  lt opt1 gt  -S  lt opt2 gt  -A  lt opt3 gt  arg1 arg2 arg3 arg4 --test      In the above example all defined arguments must be passed by the user  else the parser will detect a wrong usage  In case the --test switch is to be optional  or any other argument   assign theRoot as follows    theRoot   new AndConditionImpl  r  s  a  arg1  arg2  arg3  arg4  new OptionalImpl  test       Then your syntax looks as follows   Usage  MyProgramm -r  lt opt1 gt  -S  lt opt2 gt  -A  lt opt3 gt  arg1 arg2 arg3 arg4  --test    The full example for your case you find in the StackOverFlowExamle  You can use AND  OR  XOR conditions and any kind of nesting     hope this helps      Evaluate the parsed arguments as follows  r getValue      or if  test getValue      true         LOGGER info   r          r getValue      LOGGER info   S          s getValue      LOGGER info   arg1       arg1 getValue      LOGGER info   arg2       arg2 getValue      LOGGER info   arg3       arg3 getValue      LOGGER info   arg4       arg4 getValue      LOGGER info   test       test getValue           LOGGER info   A          a getValue

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Simple code for command line in java   class CMDLineArgument       public static void main String args                  String name args 0           System out println name

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I like this one  Simple  and you can have more than one parameter for each argument   final Map lt String  List lt String gt  gt  params   new HashMap lt  gt      List lt String gt  options   null  for  int i   0  i  lt  args length  i          final String a   args i        if  a charAt 0      -             if  a length    lt  2                System err println  Error at argument     a               return                     options   new ArrayList lt  gt             params put a substring 1   options             else if  options    null            options add a             else           System err println  Illegal parameter usage            return            For example   -arg1 1 2 --arg2 3 4  System out print params get  arg1   get 0       1 System out print params get  arg1   get 1       2 System out print params get  -arg2   get 0       3 System out print params get  -arg2   get 1       4

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You could just do it manually   NB  might be better to use a HashMap instead of an inner class for the opts       convenient  -flag opt  combination    private class Option        String flag  opt       public Option String flag  String opt    this flag   flag  this opt   opt       static public void main String   args        List lt String gt  argsList   new ArrayList lt String gt           List lt Option gt  optsList   new ArrayList lt Option gt         List lt String gt  doubleOptsList   new ArrayList lt String gt          for  int i   0  i  lt  args length  i              switch  args i  charAt 0             case  -               if  args i  length  lt  2                  throw new IllegalArgumentException  Not a valid argument    args i                if  args i  charAt 1      -                     if  args i  length  lt  3                      throw new IllegalArgumentException  Not a valid argument    args i                       --opt                 doubleOptsList add args i  substring 2  args i  length                  else                   if  args length-1    i                      throw new IllegalArgumentException  Expected arg after    args i                       -opt                 optsList add new Option args i   args i 1                     i                              break          default                 arg             argsList add args i                break                         etc

[java] Parsing arguments to a Java command line program

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