Compiling and running a Java application on Mac OSX, or any major operating system, is very easy. Apple includes a fully-functional Java runtime and development environment out-of-the-box with OSX, so all you have to do is write a Java program and use the built-in tools to compile and run it.

Writing Your First Program

The first step is writing a simple Java program. Open up a text editor (the built-in TextEdit app works fine), type in the following code, and save the file as "HelloWorld.java" in your home directory.

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

For example, if your username is David, save it as "/Users/David/HelloWorld.java". This simple program declares a single class called HelloWorld, with a single method called main. The main method is special in Java, because it is the method the Java runtime will attempt to call when you tell it to execute your program. Think of it as a starting point for your program. The System.out.println() method will print a line of text to the screen, "Hello World!" in this example.