The Main Method in Java

A cinema can have many doors, but the ticket says which one to enter by. For a Java program, that door is the main method. When you run java Ticket, the JVM looks for one specific method, with one specific shape, and starts there. Every word in that line has a job.

The Line Everyone Writes

public class Ticket {
    public static void main(String[] args) {
        System.out.println("Show starts at 6:30 PM");
    }
}

Show starts at 6:30 PM

What Each Word Means

You can also write String... args or String args[], and the name args can be anything, such as String[] words. Those are all the same method to the JVM. But keep the usual form: every Java developer recognizes it instantly.

Command-Line Arguments

Whatever you type after the class name becomes the args array. This program greets a passenger and prints their seat count.

public class Greet {
    public static void main(String[] args) {
        String name = args[0];
        int seats = Integer.parseInt(args[1]);
 
        System.out.println("Namaste, " + name);
        System.out.println("Seats booked: " + seats);
        System.out.println("Arguments received: " + args.length);
    }
}

Namaste, Srihitha
Seats booked: 3
Arguments received: 2

Run it like this:

javac Greet.java
java Greet Srihitha 3

How it works

1. The terminal splits Srihitha 3 at the space, so args[0] is "Srihitha" and args[1] is "3".
2. Line 4 uses Integer.parseInt to turn the text "3" into the number 3. Arguments always arrive as text, even when they look like numbers.
3. Line 8 prints args.length, the number of arguments.

To pass a value that contains a space, put it in quotes: java Greet "Srihitha Anamaneni" 3.

Try it yourself: run java Greet Srihitha with only one argument. What happens, and why?

Newer, Shorter Forms (Java 25)

From Java 25, the launcher also accepts simpler entry points: a main that isn't static, isn't public, or takes no parameters at all, such as void main(). These are meant for small programs and learning, and the lesson "Compact Source Files and Instance Main Methods" covers them.

If a class has both, the classic main(String[] args) is chosen first. In interviews and in most existing code, you'll still see the full public static void main(String[] args), so learn that one well.

Common Mistakes

Capital M. public static void Main(String[] args) compiles, but it's a different method. The launcher can't find main and stops with Error: Main method not found in class ....

Making it private. A private main is skipped by the launcher, which gives the same "Main method not found" error.

Treating arguments as numbers. args[1] + 1 with the argument 3 gives "31", because args[1] is text. Convert it with Integer.parseInt first.

Interview Corner

Practice

1. Easy: Write a program that prints all its arguments, one per line. Hint: use args.length and args[0], args[1] and so on, or a loop if you already know one.
2. Harder: Change Greet so that if no arguments are given, it prints Usage: java Greet <name> <seats> instead of crashing.

Key Takeaways