Apache Commons CLI - First Application

Introduction

In order to create a console based application using Apache Commons CLI, we define stages.

• Definition Stage − Used to define the options used as command line arguments.

• Parsing Stage − Used to define the parser and parse the arguments using options.

• Interrogation Stage − Used to check the arguments passed and perform the business logic accordingly.

Definition Stage

Define the Options to be used as command line arguments.

// create Options object
Options options = new Options();
      
// add option "-a"
options.addOption("a", false, "add numbers");

Parsing Stage

Define the CommandLineParser. We're using DefaultParser object here.

// Create a parser
CommandLineParser parser = new DefaultParser();

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

Interrogation Stage

Check the options passed during execution and act accordingly.

// hasOptions checks if option is present or not
if(cmd.hasOption("a")) {
   System.out.println("Sum of the numbers: " + getSum(args));
} else if(cmd.hasOption("m")) {
   System.out.println("Multiplication of the numbers: " + getMultiplication(args));
}

Example - Creating First Console Application

Let's create a sample console based application, whose purpose is to get either sum of passed numbers or multiplication of passed numbers based on the options 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.Options;
import org.apache.commons.cli.ParseException;

public class CLITester {
   public static void main(String[] args) throws ParseException {
      // ***Definition Stage***
      // create Options object
      Options options = new Options();
      
      // add option "-a"
      options.addOption("a", false, "add numbers");
      
      // add option "-m"
      options.addOption("m", false, "multiply numbers");

      // ***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));
      } else if(cmd.hasOption("m")) {
         System.out.println("Multiplication of the numbers: " + getMultiplication(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;
   }
   public static int getMultiplication(String[] args) {
      int multiplication = 1;
      for(int i = 1; i < args.length ; i++) {
         multiplication *= Integer.parseInt(args[i]);
      }
      return multiplication;
   }
}

Output

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

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

java CLITester -m 1 2 3 4 5
Multiplication of the numbers: 120