This is a simple "Hello world" done with Java programming language.

This is the source code of the program:

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

Notice that System.out.println("Hello world!"); shows the string "Hello world!" on the screen.

To compile the "Hello World" program, type the following:

javac HelloWorld.java

To execute the program, type this:

java HelloWorld