Command Line Arguments in Java

In this lesson, you will learn.

• Taking Input from User in Java
• Command Line Arguments in Java
• Examples

Taking Input from User in Java

There are several ways to take input from users. Here’s a brief overview of the most common methods.

In this lesson, you will learn only command line arguments to take input from users.

Command Line Arguments

• Command-line arguments in Java are a way to pass information to a program at the time of its execution.
• They are typically used to provide input parameters or configuration settings when the application is launched.
• These arguments are passed as an array of String objects to the main method of the program.

How to Pass Command-Line Arguments

In the main method signature public static void main(String[] args), the args is an array of String that stores the command-line arguments.

During program execution, the command-line arguments are provided after the class name.

For example:

java ClassName arg1 arg2 arg3

Here, arg1, arg2, and arg3 are command-line arguments and ClassName is the name of the main class.

Example 1: Display First Argument and Its Length

public class Example1 {
    public static void main(String[] args) {
        if (args.length >= 1) {
            System.out.println("First Argument: " + args[0]);
            System.out.println("Length: " + args[0].length());
        } else {
            System.out.println("At least one argument is required.");
        }
    }
}

Execution: java Example1 Java

The argument “Java” is stored in a variable args[0].

Output

First Argument: Java
Length: 4

Example 2: Reading Two String Arguments and Concatenating

public class Example2 {
    public static void main(String[] args) {

        if (args.length >= 2) {
            String concatenated = args[0] + args[1];
            System.out.println("Concatenated String: " + concatenated);
        } else {
            System.out.println("Two arguments are required.");
        }
    }
}

Execution: java Example2 Hello World

Output

Concatenated String: HelloWorld

Example 3: Reading Numeric and Finding the Sum of Two Numbers

public class Example2 {
    public static void main(String[] args) {
        if (args.length >= 2) {
            int sum = Integer.parseInt(args[0]) + Integer.parseInt(args[1]);
            System.out.println("Sum: " + sum);
        } else {
            System.out.println("Two numeric arguments are required.");
        }
    }
}

Execution: java Example 10 20

The method parseInt() belongs to the Integer class under java.lang package. This method is used to convert a string value to an integer.

Output

Sum: 30

Explanation

Integer.parseInt(args[0]) and Integer.parseInt(args[1]):

• Converts the command-line arguments (strings) to integers.
• args[0] and args[1] are the first and second elements of the args array.

Note: Similarly, we can use the parseDouble() and parseFloat() method to convert the string into double and float respectively.

Note: If the arguments cannot be converted into the specified numeric value then an exception named NumberFormatException occurs.

End of the lesson….enjoy learning

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