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

public class AnimationOneThread extends Applet
                                implements Runnable {

//----------------------------------------------------
/** Sequence through an array of 15 images.
 *  A thread controls the image index to display.
 *  Overrides update to avoid flicker problems.
 */

  private static final int numImages = 15;
  private Image[] images;
  private int     index;
  private Thread  Duke = null;

  public void init() {
    // load images
    images = new Image[ numImages ];
    for ( int i=0; i<numImages ; i++ )
      images[i] = getImage( getCodeBase(),
                         "images/T" + i + ".gif");
    setBackground( Color.white );
  }

  public void start() {
    if (Duke == null) {
      Duke = new Thread(this);
      Duke.start();
    }
  }

  //----------------------------------------------------
  /** Skip the usual screen-clearing step of update
   *  so that there is no "flicker" between each 
   *  drawing step.
   */
  public void update(Graphics g) {
    paint(g);
  }

  //----------------------------------------------------
  /** Draw corresponding Duke image on left part of 
   *  applet and right part of applet.
   */
  public void paint(Graphics g) {
    g.drawImage(images[ index ], 0, 0, this);
    g.drawImage(images[ numImages - index -1 ],
                                        200, 0, this);
  }


  //----------------------------------------------------
  /** The index into image array is incremented
   *  once each time through the while loop, call
   *  repaint, and pauses for a moment. The
   *  paint method will perform image drawing.
   *  While loop will terminate when Duke is set to 
   *  null.
   */
  public void run() {
    index = -1;
    Thread myThread = Thread.currentThread();
    while (Duke == myThread) { // While Duke not null
      if ( ++index >= numImages ) index = 0;
        repaint();
        try { 
          Thread.sleep(100); 
        } catch ( InterruptedException e )
        { break; }  // break while loop
    }
  }

  //----------------------------------------------------
  /** When the Applet's stop method will be called Duke
   *  will be set to null as a flag to stop the while
   *  loop in run method.
   */
  public void stop() {
    if (Duke != null) {
      Duke = null;
    }
  }
}