Lesson One - HelloWorld Applet

The APPLET Tag

   <APPLET code="HelloWorld.class" width=150 height=100></APPLET>

Program Listing

import java.awt.*;
import java.applet.*;

public class HelloWorld extends Applet 
{
  /** the init() mehtod is automatically called when the applet starts
   *
   *  Normally, you would put initialization code for ANY Java class
   *  in the class's constructor.
   *
   *  However, for classes derrived from Applet, the initialization
   *  code is placed into the method init().  This is so that the web
   *  browser will can call the init() method whenever the applet is
   *  restarted.  (It would be impossible for the web browser to call
   *  the constructor when restarting the applet.)  */
  public void init() 
  {
    // setBackground() and setForeground() are methods derrived
    // indirectly from class java.awt.Component.
    setBackground (Color.black);
    setForeground (Color.white);
  }
  

  /** the paint() method is automatically called when the web browser
   *  needs to "paint" the applet.  Painting happens when the applet
   *  is initially mapped onto the screen, and when portions need to
   *  be redrawn because:
   *
   *   a) a piece of the applet that was covered by another window
   *      gets uncovered
   *   b) the window gets resized
   *   c) another part of the program asks the applet to redraw itself
   *      (used for animation)
   *
   * @param g an object of type Graphics; it's clipping region is set
   *          to the area that needs to be repainted, and it's color is set
   *          to the applet's foreground color */
  public void paint (Graphics g) 
  {
    // invoke the method drawString in class Graphics
    g.drawString ("Hello World", 25, 50);
  }
}