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...

Answer 1

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());         }     }  

Answer 2

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<String> argsList = new ArrayList<String>();       List<Option> optsList = new ArrayList<Option>();     List<String> doubleOptsList = new ArrayList<String>();      for (int i = 0; i < args.length; i++) {         switch (args[i].charAt(0)) {         case '-':             if (args[i].length < 2)                 throw new IllegalArgumentException("Not a valid argument: "+args[i]);             if (args[i].charAt(1) == '-') {                 if (args[i].length < 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 }