starfield2.java

java 完全探索的随书源码

// StarField2.java

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

public class StarField2 extends Applet implements Runnable
{
   Thread t;
   int counter;
   Image buffer;
   Graphics bkContext;

   Color starColors [] = { Color.white, Color.darkGray, Color.lightGray,
                           Color.blue, Color.yellow };

   public void init ()
   {
      buffer = createImage (getSize ().width, getSize ().height);
      bkContext = buffer.getGraphics ();
   }

   public void start ()
   {
      if (t == null)
      {
          t = new Thread (this);
          counter = 0;
          t.start ();
      }
   }

   public void stop ()
   {
      t = null;
   }

   public void run ()
   {
      Thread current = Thread.currentThread ();

      while (t == current)
      {
         // Prepare the frame.

         // When there are enough stars, redraw the background
         // and erase visible stars.

         if (counter == 0)
         {
             bkContext.setColor (Color.black);
             bkContext.fillRect (0, 0, getSize ().width, getSize ().height);
         }

         // Set the next star's color and draw this star.

         bkContext.setColor (starColors [rnd (starColors.length)]);

         int x = rnd (getSize ().width);
         int y = rnd (getSize ().height);

         bkContext.drawLine (x, y, x, y);

         // Draw frame

         repaint (); // This method causes the update method to be called.

         // Pause

         try
         {
            Thread.sleep (50);
         }
         catch (InterruptedException e) {}
         
         // Manipulate counter

         if (++counter > 500)
             counter = 0;
      }
   }

   public void paint (Graphics g)
   {
      g.drawImage (buffer, 0, 0, this);
   }

   // Return a random integer from 0 through limit - 1.

   int rnd (int limit)
   {
      return (int) (Math.random () * limit);
   }

   public void update (Graphics g)
   {
      paint (g);
   }
}