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Java Command Line Arguments

? Java Command Line Arguments

? Quick Overview

Command line arguments in Java allow you to pass data to a program when it is executed. These values are received inside the main method and are useful for dynamic input without user interaction.

? Key Concepts

  • Arguments are passed when running the program
  • They are stored in a String[] args array
  • Index starts from 0
  • All values are treated as strings

? Syntax / Theory

The main method signature supports command line arguments using a string array parameter.

? View Code Example 
// Main method receiving command line arguments
public static void main(String[] args) {
System.out.println("Arguments count: " + args.length);
}

? Code Example(s)

? View Code Example 
// Program to print all command line arguments
class CommandLineDemo {
public static void main(String[] args) {
for(int i = 0; i < args.length; i++) {
System.out.println("Argument " + i + ": " + args[i]);
}
}
}

? Interactive Simulator

Type arguments below (separated by spaces) to see how Java stores them in the array.

> java MyClass

Internal Memory (args Array):

Waiting for input...
// Console Output will appear here...

?️ Live Output / Explanation

Example Run

java CommandLineDemo Java Python C++

Output:

Argument 0: Java
Argument 1: Python
Argument 2: C++

✅ Tips & Best Practices

  • Always check args.length before accessing values
  • Convert arguments to numbers using parsing methods if needed
  • Use meaningful argument order for clarity

? Try It Yourself

  • Write a program to add two numbers using command line arguments
  • Pass your name and age and display a formatted message
  • Handle missing arguments safely