Command Line Arguments in Java

Command line arguments allow users to pass additional information to a program at runtime. In Java, these arguments are passed as an array of strings to the main method of a class.

For example, consider the following program that prints the output of the sum of two numbers:

public class Main {
  public static void main(String[] args) {
    int num1 = Integer.parseInt(args[0]);
    int num2 = Integer.parseInt(args[1]);
    int sum = num1 + num2;
    System.out.println("Sum: " + sum);

To run this program and pass in the two numbers, we can use the following command:

java Main 10 20

This will output “Sum: 30” to the console.

It’s important to note that the indices of the args array corresponds to the position of the arguments on the command line. In this example, args[0] is "10" and args[1] is "20".

We can also use command line arguments to pass in additional options or flags to a program. For example, we might have a program that takes a -v flag to enable verbose mode. In this case, we could use the following command to run the program in verbose mode:

java Main -v

To check for the presence of a flag in the args array, we can use an if statement:

if (args[0].equals("-v")) {
  // Enable verbose mode

Command line arguments in Java can be a powerful tool for customizing the behavior of a program at runtime. Whether we are looking to pass in data, enable certain features, or just give users additional flexibility, they’re worth considering as part of your Java development toolkit.