Get Started with Java

Alright, enough talking. Let us get Java running on your machine and write some code. Trust me, the first time you compile and run a Java program, it feels good.

Installing the JDK

To write Java, you need the JDK — Java Development Kit. This includes the compiler (javac), the runtime (java), and a bunch of useful tools. Here is what you need to do:

1. Go to Oracle's website or Adoptium (I personally recommend Adoptium — it is open source and works great)
2. Download the installer for your operating system
3. Run the installer and follow the instructions
4. Open a terminal or command prompt and type java -version

If you see something like java version "21.0.1", you are good to go. If you get an error, make sure Java is added to your PATH — the installer usually does this automatically.

Your First Java Program

Create a new file called Main.java. Remember, the filename must match the class name. Type the following:

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

Now open your terminal, navigate to the folder where you saved Main.java, and run these two commands:

javac Main.java
java Main

The first command compiles your code and creates Main.class (the bytecode). The second command runs that bytecode on the JVM. If everything worked, you should see:

Hello, World!

I still get a little thrill every time I see that output. Silly, I know. But there is something magical about telling a computer what to do and watching it obey.

Understanding the Code

Let me quickly explain what each piece does before we move on:

• public class Main — every Java program lives inside a class. public means anyone can access it.
• public static void main(String[] args) — this is the entry point. When you run your program, Java looks for this method and starts there.
• System.out.println() — this prints text to the console. The ln part adds a new line after the text.

Do not worry about memorizing everything. You will see this pattern so many times that it will become second nature.