args parameter in Java

  1. args Parameter in the main Method in Java
  2. args Parameter as an Array in the main Method in Java
  3. args Parameter as var-args in the main Method in Java
  4. Convert args Parameter to Another Data Type in Java

This tutorial introduces what is string args parameter in the main method in Java.

In Java, the main method is an entry point of execution where Java compiler starts execution. This method has a string type parameter, basically an array(args[]). The args name is not fixed so that we can name it anything like foo[], but it should be of the string type.

Java compiler uses this parameter to get command line arguments passed during the program execution. Let’s see some examples.

args Parameter in the main Method in Java

Here, we use a for loop to iterate and display the command line arguments hold by the args array. See the example below.

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

Below is how we can supply a command-line argument to the main method during the program execution.

Java SimpleTesting Hello DelftStack

Output:

Hello
DelftStack

args Parameter as an Array in the main Method in Java

Since it is an array, so we can get argument values with index bases. The first value is present at the index as 0, and the last value is present at n-1 index, where n is the array length. See the example below.

public class SimpleTesting{ 
    public static void main(String[] args) {
        String val1 = args[0];
        String val2 = args[1];
        System.out.println(val1);
        System.out.println(val2);
        }  
    }
}

Output:

Hello
DelftStack

args Parameter as var-args in the main Method in Java

Java allows declaring the args[] parameter as var-args which works similarly. It can also be written as the given example.

public class SimpleTesting{ 
    public static void main(String... args) {
        String val1 = args[0];
        String val2 = args[1];
        System.out.println(val1);
        System.out.println(val2);
        }  
    }
}

Output:

Hello
DelftStack

Convert args Parameter to Another Data Type in Java

The args[] parameter is of the string type, so if we wish to convert its type, we can use wrapper class methods. For example, to get an integer type value, we can use the parseInt() method. See the example below.

public class SimpleTesting{ 
	public static void main(String... args) {
		String val1 = Integer.parseInt(args[0]);
        String val2 = Integer.parseInt(args[1]);
		System.out.println(val1);
        System.out.println(val2);
		}  
	}
}

Run the code as below.

Java SimpleTesting 10 20

Output:

10
20
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