import java.applet.*;
import java.awt.*;
public class zj extends Applet implements Runnable
{ 
  int x,y,m=100,n=100;
  Thread th1=null,th2=null,th3=null;//th1為控制車輛的線程，th2為控制交通燈的線程,th3為顯示名字得線程
  Font f=new Font("宋體",Font.BOLD,24);
  String str="4991252 31 張進";
  Image img[]=new Image[2];  //用數組控制兩輛車的加載
  Image offimg;
  Graphics offg;//定義Graphics對象，用一實現雙緩沖
  int t=0;
  int tag=0;
  boolean isRed=false,
	  isYellow=false,
	  isGreen=true;
     public void init()
    {
	//加載圖片的初始化
	 for(int i=0;i<2;i++)
	img[i]=getImage(getDocumentBase(),i+".gif");
	x=0;
	y=this.getSize().height/2;
 	offimg=createImage(800,600);
	offg=offimg.getGraphics();
   }
  public void start()
   {   
	if(th1==null)
	{
		th1=new Thread(this);
		th1.start();
	}
	if(th2==null)
	{
		th2=new Thread(this);
		th2.start();
	}
	if(th3==null)
	{
		th3=new Thread(this);
		th3.start();
	}
   }
  
 public void run()
  { 
    while(th1==Thread.currentThread())
      {
	  x+=5;
	  try{th1.sleep(30);}
	  catch(Exception e) {}
	  repaint();
     	  if(x>=200&&x<=400)
		{
		  if(isRed)
		    {
			try{th1.sleep(5000);
			if(isGreen)
			 th1.resume();}
			catch(Exception e) {}
		     }
		   if(isYellow)
		     { 
			if(tag==0)
			{
			  try{th1.sleep(50);
			 if(isGreen)
			  th1.resume();
		           }
			catch(Exception e) {}
		       }
			if(tag==1)
			{
			  try{th1.sleep(50);
			 if(isRed)
			  th1.suspend();
		           }
			catch(Exception e) {}
		       }
		     }
		 }
	  if(x==this.getSize().width)
		{  	
 			x=0;
			t++;//交替車輛
			if(t==2) t=0;
			repaint();
		}
	 
	
       }
   while(th2==Thread.currentThread())
   {
		if(isRed)
		  {
			try{th2.sleep(5000);
			    isRed=false;
			    isYellow=true;
			    isGreen=false;
			    repaint();
			   }
			catch(Exception e) {}
		   }
		if(isYellow)
		  {	
			if(tag==0)
			{
			 try{th2.sleep(2000);
			    isYellow=false;
			    isGreen=true;
			    isRed=false;
			    repaint();
			   }
			 catch(Exception e) {}
			}
		}
		if(isGreen)
		  {
			try{th2.sleep(5000);
			        isYellow=true;
				isRed=false;
				isGreen=false;
				tag=1;
			    repaint();
			   }
			catch(Exception e) {}
		 }	
		if(isYellow)
		 {	
			if(tag==1)
			{
			 tag=0;
			 try{th2.sleep(2000);
			    isYellow=false;
			    isGreen=false;
			    isRed=true;
			    repaint();
			   }
			 catch(Exception e) {}
			}
	 	}
     }
   while(th3==Thread.currentThread())
    {
		m++;
		n++;
		if(m==300)
		{
			m=100;
			n=100;
		}
		repaint();
		try{th3.sleep(100);}
		catch(Exception e) {}	
    }
  }
 public void update(Graphics g)
 {	//設置背景色
        offg.setColor(Color.blue);
        offg.fillRect(0,0,800,600);
        offg.setColor(Color.magenta);
	offg.setFont(f);
	offg.drawString(str,m,n);
	//畫斑馬線
	offg.setColor(Color.black);
	offg.fillRect(550,385,230,2);
	offg.fillRect(525,400,230,2);
	offg.fillRect(500,415,230,2);
	offg.fillRect(475,430,230,2);
	offg.fillRect(450,445,230,2);
	offg.fillRect(425,460,230,2);
	offg.drawImage(img[t],x,380,this);//加載圖片
	offg.setColor(new Color(80,100,140));
	offg.fillRect(600,60,4,200);
	offg.drawRect(525,30,150,30);
	if(isRed)//當前燈為紅燈，用紅色填充第一個燈，其他兩個燈用灰色填充
	{ offg.setColor(Color.red);
	  offg.fillOval(535,30,30,30);
	  offg.setColor(Color.gray);
	  offg.fillOval(585,30,30,30);
	  offg.fillOval(635,30,30,30);
  	}	
	if(isYellow)//當前燈為黃燈，用黃色填充第二個燈，其他兩個燈用灰色填充
	{ offg.setColor(Color.yellow);
	  offg.fillOval(585,30,30,30);
	  offg.setColor(Color.gray);
	  offg.fillOval(535,30,30,30);
	  offg.fillOval(635,30,30,30);
  	}	
	if(isGreen)//當前燈為綠燈，用綠色填充第三個燈，其他兩個燈用灰色填充
	{ offg.setColor(Color.green);
	  offg.fillOval(635,30,30,30);
	  offg.setColor(Color.gray);
	  offg.fillOval(535,30,30,30);
	  offg.fillOval(585,30,30,30);
  	}       
	g.drawImage(offimg,0,0,this);//用offg、offimg實現雙緩沖，消除屏幕的閃爍現象
 }
}