How do I get the command line arguments passed to the program?

When we create a Java application we might want to pass a couple of parameters to our program. To get the parameters passed from the command line we can read it from the main(String[] args) method arguments.

To make a class executable we need to create a main() method with the following signatures:

public static void main(String[] args) {
}

This method takes an array of String as the parameter. This array is the parameters that we pass to the program in the command line.

package org.kodejava.basic;

public class ArgumentParsingExample {
    public static void main(String[] args) {
        for (int i = 0; i < args.length; i++) {
            System.out.println("Argument " + (i + 1) + " = " +
                    args[i]);
        }

        // If you want to check if the number of supplied parameters
        // meet the program requirement you can check the size of 
        // the arguments array.
        if (args.length < 3) {
            System.out.println(
                    "You must call the program as follow:");
            System.out.println(
                    "java org.kodejava.example.basic.ArgumentParsingExample arg1 arg2 arg3");

            // Exit from the program with an error status, for
            // instance we return -1 to indicate that this program 
            // exit abnormally
            System.exit(-1);
        }

        System.out.println("Hello, Welcome!");
    }
}

When we try to run the program without argument we will see the following message:

$ java org.kodejava.basic.ArgumentParsingExample
You must call the program as follow:
java org.kodejava.basic.ArgumentParsingExample arg1 arg2 arg3

And when we pass three arguments we get something like:

$ java org.kodejava.basic.ArgumentParsingExample param1 param2 param3
Argument 1 = param1
Argument 2 = param2
Argument 3 = param3
Hello, Welcome!

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Wayan

Founder at Kode Java

A programmer, runner and recreational diver, lives on the island of Bali, Indonesia. Programming in Java, Spring Framework, Hibernate / JPA, MySQL. To support me working on this project, buy me a cup of coffee, every little bit helps. Thank you.

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