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Hello World Program

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The "Hello, World!" Program: A Fun and Engaging Introduction to Java​

In any programming language, a "Hello, World!" program is the gateway to coding—a simple yet powerful incantation that magically brings text to life on your screen. Think of it as your first "hello" to the coding universe, a warm-up before diving into more complex spells (a.k.a. real-world applications).

In this tutorial, we’ll explore how to write a "Hello, World!" program in Java, from the latest Java 21 features to the traditional verbose approach. Buckle up, because it’s going to be an amusing ride!

1. Java Hello World Program – Java 21 and Later 🚀​

Since Java 21, coding newbies get a little gift: unnamed classes and instance main methods. This means we can write Java programs with minimal syntax. Less boilerplate, more fun!

Here’s how simple it gets:

HelloWorld.java​

void main() {
    System.out.println("Hello, World!");
}

Yes, that's the whole program! Just save it as HelloWorld.java and run it. It’s like Java finally decided to give us a break.

When executed, you’ll see:

Hello, World!

And just like that, you're officially a Java developer! 🎉

2. Java Hello World Program [≤ Java 20] 🏛️​

Before Java 21, we had to be a little more "formal" (read: verbose). Here’s the classic way to print "Hello, World!":

HelloWorld.java​

public class HelloWorld {

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

🔍 Key Observations:

  • public class HelloWorld: Java is an object-oriented language, so everything goes inside a class.
  • public static void main(String[] args): The main method is the program’s entry point.
  • System.out.println("Hello, World!");: The magic spell that prints our message!

💡 Pro Tip: Write it yourself instead of copy-pasting. It'll help you understand Java’s case sensitivity better. (Trust me, missing a capital letter here and there will haunt you later!)

3. Compiling and Executing the Program ⚙️​

Unlike some languages where you can just run the source file directly (cough Python cough), Java requires an extra step: compilation.

Step 1: Compile the Program​

javac HelloWorld.java

This creates a HelloWorld.class file containing Java bytecode. But bytecode isn’t directly executable—Java needs its own special interpreter, the Java Virtual Machine (JVM).

Step 2: Run the Program​

java HelloWorld

Output:

Hello, World!

🔴 Important: Don’t include the .class extension when running the file. Just type java HelloWorld, not java HelloWorld.class.

Bonus: Running a Java 11+ Program Without Compilation​

Since Java 11, you can skip the explicit compilation step for simple single-file programs. Just run:

java HelloWorld.java

It's like Java finally realized that life is too short for unnecessary steps!

4. How Does It Work? 🧐​

Let’s break down the classic Java 20 and earlier version:

public static void main(String[] args) { ... }

Deep Dive into the Main Method:​

  • public: Allows JVM to call this method from anywhere.
  • static: Lets Java execute it without needing an object of the class.
  • void: Means this method doesn’t return anything.
  • main: The method name—Java looks for this when starting execution.
  • String[] args: An array to accept command-line arguments (not needed here but useful later!).

And then we have:

System.out.println("Hello, World!");
  • System.out: Standard output stream.
  • println: Prints the text with a newline at the end.

So, when you put everything together, Java sees this as:

  1. "Okay, I found the main method!"
  2. "There's a command to print something. Let's display it."
  3. "Mission accomplished!"

And boom—"Hello, World!" appears on your screen! 🎆

Conclusion 🎯​

Writing your first Java program is like saying "hello" to a new adventure. With Java 21, things have gotten a lot simpler, but knowing the classic way is still essential. Now that you’ve mastered this first step, you’re ready to explore more complex concepts—variables, loops, and beyond!

Happy coding! 🚀