/** USE EXISTING JAVA CLASSES **/

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

/** EXTEND THE JAVA APPLET CLASS AND IMPLEMENT THE RUNNABLE INTERFACE **/

public class AnimatorApplet1 extends Applet implements Runnable
   {int frameNumber = -1;                // Define and/or initialize some
    int delay;                                     // AnimatorApplet1 class variables.
    Thread animatorThread;
    boolean frozen = true;
    Font font=new Font("TimesRoman",Font.BOLD,30);
    String framestr = "";

    /** INITIALIZE THE APPLET **/

    public void init()
       {String str;
        int fps = 10;                             // Define the default fps (frames per second).
        str = getParameter("fps");         // Possibly, get HTML string specifying the
        try                                           // fps.
         {if (str != null)
           {fps = Integer.parseInt(str);}  // If possible, convert HTML fps to an
          }                                            // integer.
        catch (Exception e) {}              // In case the try caused something strange.
        delay = (fps > 0) ? (1000/fps): 100;  // Convert fps to the milisecond delay
        }                                                      // time between frames.

    /** CLICK TO START OR STOP THE APPLET **/

    public boolean mouseDown(Event e, int x, int y)
       {if (frozen)
         {frozen = false;
          start();}
        else
         {frozen = true;
          stop();}
        return true;
        }
 

Toggle your browser's Back and Forward buttons to compare the running applet to this code.

Click here to run a fresh copy of the applet:  AnimatorApplet1.html

 
   /** GENERATE AND/OR START THE ANIMATION THREAD **/

   public void start()
       {if (frozen) { }                            // The animation is supposed to stay frozen.
        else                                           // Otherwise, generate and/or start the
         {if (animatorThread == null)      // animation thread. Apparently, if run
           {animatorThread = new Thread(this);}  // breaks after catching an exception,
          animatorThread.start();                           // the animatorThread though not null
          }                                                            // will still need to be restarted.
        }

    /** CREATE AND DISPLAY FRAMES OF THE ANIMATION THREAD **/

    public void run()
       {setBackground(Color.white);
        Thread.currentThread().setPriority(Thread.MIN_PRIORITY);  // Set low priority.
        long startTime = System.currentTimeMillis();                    // Remember start time.
        while (Thread.currentThread() == animatorThread)          // The animation loop.
           {frameNumber++;                                               // Advance the frame number.
            framestr = "Frame " + frameNumber;                  // Create the frame string.
            repaint();                                                            // Display the frame.
            try                                                                      // Sleep for the delay period.
             {startTime += delay;
              Thread.sleep(Math.max(0,
                                    startTime-System.currentTimeMillis()));
              }
            catch (InterruptedException e) {break;}     // In case the try caused
            }                                                               // something strange, exit
        }                                                                   // the while loop.
 

Toggle your browser's Back and Forward buttons to compare the running applet to this code.

Click here to run a fresh copy of the applet:  AnimatorApplet1.html

 
   /** CREATE THE CURRENT FRAME OF THE ANIMATION THREAD **/

   public void paint(Graphics g)
       {g.setFont(font);
        g.setColor(Color.blue);
        g.drawString(framestr,140,110);
        }

    /** STOP THE ANIMATION THREAD **/

    public void stop()
       {animatorThread = null;}  // The user either clicked to stop or left the page,
    }                                         // so wipe out the current thread.