三十八毒

//接口ClockScreen.java
package test.wkjava;
public interface ClockScreen {	
	public void showTime(int hour,int min,int sec);
}
//类Clock.java
package test.wkjava;
import java.util.Collection;
import java.util.Iterator;
import java.util.Vector;
public class Clock {	
	private Timer timer;	
	private int hour;
	private int min;
	private int sec;	
	private long start;
	private long end;
	private long now;	
	private long show;	
	private Collection screens;
	private boolean pauseFlag;	
	public Clock(){
		super();
		screens = new Vector();
	}	
	public void start(int hour,int min,int sec){
		if (isClockRun()){
			return;
		}
		this.hour = hour;
		this.min = min;
		this.sec = sec;		
		start = System.currentTimeMillis();
		end = start + hour*60*60*1000 + min*60*1000+ sec*1000;		
		timer = new Timer();		
		timer.start();
	}	
	private boolean isClockRun() {
		return timer != null && timer.isAlive();
	}	
	public void addScreen(ClockScreen screen){
		synchronized(screens){
			this.screens.add(screen);
		}
	}	
	public void removeScreen(ClockScreen screen){
		screens.remove(screen);
	}	
	private class Timer extends Thread{		
		public void run(){			
			pauseFlag = false;    			
			while(true){				
				synchronized(screens){
					for (Iterator i=screens.iterator();i.hasNext();){
						ClockScreen scr = (ClockScreen)i.next();
						scr.showTime(hour,min,sec);
					}
				}				
				synchronized (Clock.this) {
					if (pauseFlag == true)
						break;
				}			
				synchronized(Clock.this){
					if(hour==0 && min==0 && sec==0)
						break;
					now = System.currentTimeMillis();
					show = end - now;					
					hour = (int) (show/1000/60/60);
					min = (int)((show/1000/60)%60);
					sec = (int)((show/1000)%60);					
					try {
						Thread.sleep(1000);
					} 
					catch (InterruptedException e) {
						e.printStackTrace();
					}					
				}
			}			
		}		
    }
	public synchronized void stop() {		
		hour = 0;
		min = 0;
		sec = 0;		
	}
	public void pause() {
		synchronized (Clock.this) {
			pauseFlag = true;	
		}	
	}
	public void contine() {
		start(hour,min,sec);
	}
}
//倒记时实现
package test.wkjava;
public class TestClock {
	public TestClock() {		
		Clock clock = new Clock();		
		clock.addScreen(new ClockScreen(){			
			public void showTime(int hour,int min,int sec){				
				System.out.println(hour+"小时"+min+"分"+sec+"秒");				
			}
		});		
		clock.start(5,5,5);		
	}	
	public static void main(String[] args) {
         new TestClock();
	}
}