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Your First Java Program

Now that your environment is set up, let's write and run your first Java program!

Create HelloColy.java​

Create a new file called HelloColy.java and add the following code:

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

Understanding the Code​

Let's break down what each part means:

  • public class HelloColy: Declares a class named HelloColy
  • public static void main(String[] args): The entry point of every Java program
  • System.out.println(): Prints text to the console

Compile and Run​

Open your terminal in the directory where you saved the file and run:

javac HelloColy.java

This compiles your Java code into bytecode. You should now see a HelloColy.class file.

Now run the program:

java HelloColy

You should see the output:

Hello, COLY!

Congratulations! You've just run your first Java program!

note

The filename must match the class name. Since our class is HelloColy, the file must be HelloColy.java.

Next Steps​

Now that you've written your first program, let's learn about variables - how to store and work with data in Java.