Your First Java Program — Line by Line

The only explanation you need to truly understand your first Java program.

Let’s begin your Java journey with the very first program every programmer writes:

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

This post breaks down each line of code in simple, beginner-friendly terms — so you don’t just run the program but actually understand what’s happening.

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🧩 Line 1: public class HelloWorld

Let’s decode it:

• public – This keyword means the class is accessible from anywhere. It's like saying: "Hey world, you’re allowed to see this class!"

• class – A class is like a blueprint. It defines what your program looks like and what it can do.

• HelloWorld – This is the name of your class. By Java convention, class names use PascalCase and match the filename (e.g., HelloWorld.java).

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🔑 Line 2: public static void main(String[] args)

Each keyword here serves a special purpose:

• public – Just like before, this means anyone can access this method.

• static – You don’t need to create an object of the class to run this method. It belongs to the class itself.

• void – This means the method doesn’t return anything.

• main – This is the starting point of any Java program. Java looks for this method to begin execution.

• String[] args – A fancy way of saying: “Hey, I can take inputs from the command line.”

You can also write this as String... args — which is a shorthand for accepting multiple arguments (varargs).

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💡 Pro Tip

Think of the main method as the front door to your program. Java always knocks here first.

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Nitin
Hashnode | Substack | LinkedIn | GIT

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