上一篇講到執行緒的同步，

今天要跟大家分享的是執行緒的等待與喚醒，

Object物件中提供wait() notify() notify All()方法，

可以讓執行緒間相互設定等待和喚醒。

1. Wait():讓指定的執行緒進入Wait pool成為等待狀態，每個物件都有自己專有的Wait pool。

2. notify():喚醒一個在Wait pool等待的執行緒，被喚醒的執行緒由JVM決定。

3. notifyAll():喚醒所有在Wait pool等待的執行緒，先後順序由JVM決定。

   class Ball {
   private boolean isThrow = false;
   public synchronized void throwF(int tNo) {
   while (isThrow) {
   try {
   wait();
   } catch (InterruptedException e) {}
   }
   System.out.println("丟出第 " + tNo + " 顆球");
   isThrow = true;
   notify();
   }

    public synchronized void accessF(int aNo) { 
    	while (!isThrow) {  
    		try {
    			wait();  
    		} catch (InterruptedException e) {}
    	}
    	System.out.println("接到第 " + aNo + " 顆球");		
    	isThrow = false; 	
    	notify(); 
    }
   

   }

   class ThrowFrisbee implements Runnable {
   Ball frisbee;
   ThrowFrisbee(Ball frisbee) {
   this.frisbee = frisbee;
   }
   public void run() {
   for (int i = 1; i <= 5; i++) {
   frisbee.throwF(i);
   }
   }
   }

   class AccessFrisbee implements Runnable {
   Ball frisbee;
   AccessFrisbee(Ball frisbee) {
   this.frisbee = frisbee;
   }
   public void run() {
   for (int i = 1; i <= 5; i++) {
   frisbee.accessF(i);
   }
   }
   }

   public class WaitNotify {
   public static void main(String[] atgs) {
   Ball frisbee = new Ball();
   Thread master = new Thread(new ThrowFrisbee(frisbee));
   Thread dog = new Thread(new AccessFrisbee(frisbee));
   master.start();
   dog.start();
   }
   }