/*  ParticleApplet.java
 */

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

public class ParticleApplet extends Applet
{
   protected Thread[] threads = null;   // null when not running

   protected final ParticleCanvas canvas
                             = new ParticleCanvas(200);  // BB was 100

   public void init() { add(canvas); }

   protected Thread makeThread(final Particle p)  // utility
   {
     Runnable runloop = new Runnable() {
       public void run()
       {
         try {
           for(;;) {
             p.move();
             canvas.repaint();
             Thread.sleep(100);  // 100msec is arbitrary
           }
         }
         catch (InterruptedException e) { return; }
       }
     };
     return new Thread(runloop);
   }

   public synchronized void start()
   {
     int n = 10;     // just for demo

     Random rng = new Random();

     if (threads == null) { // bypass if already started
       Particle[] particles = new Particle[n];
       for (int i = 0; i < n; ++i)
         particles[i] = new Particle(85+rng.nextInt(100), 80+rng.nextInt(100));
         //particles[i] = new Particle(50, 50);    //BB  original
       canvas.setParticles(particles);

       threads = new Thread[n];
       for (int i = 0; i < n; ++i) {
         threads[i] = makeThread(particles[i]);
         threads[i].start();
       }
     }
   }

   public synchronized void stop() {
     if (threads != null) { // bypass if already stopped
       for (int i = 0; i < threads.length; ++i)
         threads[i].interrupt();
       threads = null;
     }
   }
}