Исходные тексты аплета Rectangles приведены в листинге 1.

Листинг 1. Файл Rectangles,java

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

public class Rectangles 
extends Applet
{
DrawRectangles m_DrawRectThread =
                           null;
DrawEllipse m_DrawEllipseThread = null;
NotifyTask m_NotifyTaskThread = null

  public String getAppletInfo()
  {
    return "Name: Rectangles";
  }

  public void paint(Graphics g)
  {
    Dimension dimAppWndDimension = getSize();

    g.setColor(Color.yellow);
    g.fillRect(0, 0, 
      dimAppWndDimension.width  - 1, 
      dimAppWndDimension.height - 1);

    g.setColor(Color.black);
    g.drawRect(0, 0, 
      dimAppWndDimension.width  - 1, 
      dimAppWndDimension.height - 1);
  }

  public void start()
  {
    if (m_DrawRectThread == null)
    {
      m_DrawRectThread = 
        new DrawRectangles(this);
      m_DrawRectThread.start();
    }

    if (m_DrawEllipseThread == null)
    {
      m_DrawEllipseThread = 
        new DrawEllipse(this);
      m_DrawEllipseThread.start();
    }

    if (m_NotifyTaskThread == null)
    {
      m_NotifyTaskThread = 
        new NotifyTask(m_DrawEllipseThread);
      m_NotifyTaskThread.start();
    }
  }

  public void stop()
  {
    if (m_DrawRectThread != null)
    {
      m_DrawRectThread.stop();
      m_DrawRectThread = null;
    }

    if (m_DrawEllipseThread == null)
    {
      m_DrawEllipseThread.stop();
      m_DrawEllipseThread = null;
    }    

    if (m_NotifyTaskThread != null)
    {
      m_NotifyTaskThread.stop();
      m_NotifyTaskThread = null;
    }
  }
}

class DrawRectangles extends Thread
{
  Graphics g;
  Dimension dimAppWndDimension;

  public DrawRectangles(Applet Appl)
  {
    g = Appl.getGraphics();
    dimAppWndDimension = Appl.getSize();
  }

  public void run()
  {
    while (true)
    {
      int x, y, width, height;
      int rColor, gColor, bColor;      

      x =      (int)(dimAppWndDimension.width 
            * Math.random());
      y =      (int)(dimAppWndDimension.height
            * Math.random());
      width  = (int)(dimAppWndDimension.width
            * Math.random()) / 2;
      height = (int)(dimAppWndDimension.height
            * Math.random()) / 2;      

      rColor = (int)(255 * Math.random());
      gColor = (int)(255 * Math.random());
      bColor = (int)(255 * Math.random());

      g.setColor(new Color(rColor, 
        gColor, bColor));
      g.fillRect(x, y, width, height);

      try
      {
	Thread.sleep(50);
      }
      catch (InterruptedException e)
      {
	stop();
      }
    }
  }
}

class DrawEllipse extends Thread
{
  Graphics g;
  Dimension dimAppWndDimension;

  public DrawEllipse(Applet Appl)
  {
    g = Appl.getGraphics();
    dimAppWndDimension = Appl.getSize();
  }

  public synchronized void run()
  {
    while (true)
    {
      int x, y, width, height;
      int rColor, gColor, bColor;

      x =      (int)(dimAppWndDimension.width
          * Math.random());
      y =      (int)(dimAppWndDimension.height
          * Math.random());
      width  = (int)(dimAppWndDimension.width
          * Math.random()) / 2;
      height = (int)(dimAppWndDimension.height
          * Math.random()) / 2;

      rColor = (int)(255 * Math.random());
      gColor = (int)(255 * Math.random());
      bColor = (int)(255 * Math.random());

      g.setColor(new Color(rColor,
         gColor, bColor));
      g.fillOval(x, y, width, height);

      try
      {
	this.wait();
      }
      catch (InterruptedException e)
      {
      }
    }
  }
}

class NotifyTask extends Thread
{
  Thread STask;

  public NotifyTask(Thread SynchroTask)
  {
    STask = SynchroTask;
  }

  public void run()
  {
    while (true)
    {
      try
      {
	Thread.sleep(30);
      }
      catch (InterruptedException e)
      {
      }

      synchronized(STask)
      {
        STask.notify();
      }
    }
  }
}