Apache Commons CLI - Option Properties

Quiz

Option object is used to represent the Option passed to command line program. Following are various properties that an Option object possess.

Option Object Properties

Sr.No	Name (Type) &amps; Description
1	opt (String) Identification string of the Option.
2	longOpt (String) Alias and more descriptive identification string.
3	description (String) Description of the function of the option.
4	required (boolean) Flag to check whether the option must appear on the command line.
5	arg (boolean) Flag to check whether the option takes an argument.
6	args (boolean) Flag to check whether the option takes more than one argument.
7	optionalArg (boolean) Flag to check whether the option's argument is optional.
8	argName (String) Name of the argument value for the usage statement.
9	valueSeparator (char) The character value used to split the argument string.
10	type (Object) Argument type.
11	value (String) Option value.
12	values (String[]) Values of the option.

Example - Usage of Option Properties - Without Mandatory Argument

Let's create a sample console based application, whose purpose is to get sum of passed numbers based on the option used.

CLITester.java

package com.tutorialspoint;

import org.apache.commons.cli.CommandLine;
import org.apache.commons.cli.CommandLineParser;
import org.apache.commons.cli.DefaultParser;
import org.apache.commons.cli.Option;
import org.apache.commons.cli.Options;
import org.apache.commons.cli.ParseException;

public class CLITester {
   public static void main(String[] args) throws ParseException {
      // create Options object
      Options options = new Options();

      // Create Option object
      Option addOption = new Option("a", "Add Numbers");
      
      // argument is required
      addOption.setRequired(true);
      
      // add option "-a"
      options.addOption(addOption);
      
      // ***Parsing Stage***
      // Create a parser
      CommandLineParser parser = new DefaultParser();

      // parse the options passed as command line arguments
      CommandLine cmd = parser.parse( options, args);

      // ***Interrogation Stage***
      // hasOptions checks if option is present or not
      if(cmd.hasOption("a")) {
         System.out.println("Sum of the numbers: " + getSum(args));
      } 
   }
   public static int getSum(String[] args) {
      int sum = 0;
      for(int i = 1; i < args.length ; i++) {
         sum += Integer.parseInt(args[i]);
      }
      return sum;
   }   
}

Output

Run the file, without passing -a as option and CLI will throw MissingOptionException −

Exception in thread "main" org.apache.commons.cli.MissingOptionException: Missing required option: a
	at org.apache.commons.cli.DefaultParser.checkRequiredOptions(DefaultParser.java:344)
	at org.apache.commons.cli.DefaultParser.parse(DefaultParser.java:770)
	at org.apache.commons.cli.DefaultParser.parse(DefaultParser.java:815)
	at org.apache.commons.cli.DefaultParser.parse(DefaultParser.java:797)
	at org.apache.commons.cli.DefaultParser.parse(DefaultParser.java:776)
	at com.tutorialspoint.CLITester.main(CLITester.java:29)

Run the file, while passing -a as option and numbers to get the sum of the numbers as result −

java CLITester -a 1 2 3 4 5
Sum of the numbers: 15

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