example7_8.java

书中的例题

import java.applet.Applet;
import java.awt.*;
public class Example7_8 extends Applet implements Runnable
{
	Thread AnimThread=null;
	ICar  LRcar,TBcar;
	TrafficCop tCop;
   public void init()
	{
      resize(400,400);
	  tCop=new TrafficCop();
      LRcar=new ICar(tCop,ICar.leftToRight,16);
	  TBcar=new ICar(tCop,ICar.topToBotton,17);
	}
   public void start()
	{
      if (AnimThread==null)
      {
		  AnimThread=new Thread(this);
		  AnimThread.start();
		  if (LRcar!=null && TBcar!=null)
		  {
			  LRcar.start();
			  TBcar.start();
		  }
      }
	  else
		{
		  AnimThread.resume();  //恢复线程运行
		  if (LRcar!=null){LRcar.resume(); }
          if (TBcar!=null){TBcar.resume(); }
		}
    }
   public void stop()
	{
		  AnimThread.suspend();  //挂起线程
		  if (LRcar!=null){LRcar.suspend(); }
          if (TBcar!=null){TBcar.suspend(); }
	}
   public void run()
	{
	   while(true)
		{
		   try{Thread.sleep(50);}
		   catch(InterruptedException e){}
		   repaint();
		}
	}
   public void paint(Graphics g)
	{
	   Color saveColor=g.getColor();
	   g.setColor(Color.black);
	   g.fillRect(0,180,400,40);
	   g.fillRect(180,0,40,400);
	   LRcar.drawCar(g);
	   TBcar.drawCar(g);
	}
   public void update(Graphics g)
	{
	   if(!isValid())
		{
		   paint(g);
		   return;
		}
	   LRcar.drawCar(g);
	   TBcar.drawCar(g);
	}
}

class ICar extends Thread
{
	public int lastPos=-1;
    public int carPos=0;
	public int speed=10;  //初始化小车速度　
	public int direction=1;//初始化小车的行驶方向
	public TrafficCop tCop;
	public final static int leftToRight=1;
    public final static int topToBotton=2;
	public ICar(TrafficCop tCop)
	{
		this(tCop,ICar.leftToRight,10);
	}
	public ICar(TrafficCop tCop, int direction, int speed)
	{
		this.tCop=tCop;
		this.speed=speed;
		this.direction=direction;
	}
    public void run()
	{
		while(true)
		{
			tCop.checkAndGo(carPos,speed);
			carPos+=speed;
			if (carPos>=400)
			  { carPos=0;	}
            try{Thread.sleep(200);}
			catch(InterruptedException e){}
		}
	}
  public void drawCar(Graphics g)         //绘制小车
	{
	  if(direction==ICar.leftToRight)     //方向判断
		{
		  if(lastPos>=0)                  //位置判断
			{
			  g.setColor(Color.black);
			  g.fillRect(0+lastPos,185,40,32);
			}
			g.setColor(Color.gray);
			g.fillOval(2+carPos,185,10,10);
            g.fillOval(26+carPos,185,10,10);
            g.fillOval(2+carPos,205,10,10);
            g.fillOval(26+carPos,205,10,10);
            g.setColor(Color.green);
            g.fillOval(0+carPos,190,40,20);
            lastPos=carPos;
		}
		else
		{
			if(lastPos>=0)
			{
				g.setColor(Color.black);
				g.fillRect(185,0+lastPos,32,40);
			}
			g.setColor(Color.gray);
			g.fillOval(185,2+carPos,10,10);
			g.fillOval(185,26+carPos,10,10);
			g.fillOval(205,2+carPos,10,10);
			g.fillOval(205,26+carPos,10,10);
			g.setColor(Color.yellow);
			g.fillRect(190,0+carPos,20,40);
			lastPos=carPos;
		}
	}
	public void updateCar(Graphics g)  //更新
	{
		if (lastPos!=carPos)
		{
			drawCar(g);
		}
	}
}

class TrafficCop   //该类用于ICar线程的控制
{
  private boolean IntersectionBusy=false;
  //同步化方法
  public synchronized void checkAndGo(int carPos,int speed)
	{
	 if(carPos+40<180 && carPos+40+speed>=180 && carPos+speed<=220)
		{
			while(IntersectionBusy)
			{
				try{ wait();}
				catch(InterruptedException e){}
			}
		
         IntersectionBusy=true;
	}
	if(carPos+speed>220)
	{
      IntersectionBusy=false;
	}
	notify();     //线程退出等待状态
  }
}