Hello World !

This is a first/simple example of a Java program.

1. Take an editor and make a new file called Hello.java with the following code:

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

• A class is a re-usable piece of software that as a name (starting with an Uppercase !) and is saved with a .java extension.
• The main program is an operation proposed by this class ; the operation takes an array [] of texts called args from the class String.
• Another sample class is System that represents the computer with its keyboard (in property/attribute) and screen (out property).
• This latter is also an illustration of (static) object that proposes an operation to print a text (String) with a new line at end (see 'ln' at end of print).