java 用PV 实现哲学家吃面问题的一个线程问题 （在线等啊！）

[hnd201031000407]

class Semaphore {
	int status;				//筷子当前状态
	 int num;				//筷子编号
	public Semaphore(int status, int num) {    //筷子信号量
		this.status = status;
		this.num = num;
	}
}




public class philosopherProblem {
	static Semaphore fork[] = new Semaphore[5];
	philosopher p[] = new philosopher[5];
	int pw[] = new int[5];
	

		public synchronized void P(philosopher phi, Semaphore fork) {   //p操作
			fork.status--;
			
			if (fork.status < 0) {
				try {
					pw[fork.num] = phi.num;					//当筷子已经被占用的时候，用pw来记录哪根筷子有哲学家在等待。
					this.wait();
					
				} catch (InterruptedException e) {

					e.printStackTrace();
				}
			}
		}

		public synchronized void V(philosopher phi, Semaphore fork) {
			fork.status++;

			if (fork.status <= 0) {

			
				if (pw[fork.status] != -1) {					//如果刚放下的筷子中有哲学家在等，则查看pw中是哪个哲学家，然后再运行这个哲学家线程	
						//notifyAll();
					p[ pw[fork.status] ].notify();			
					pw[fork.status] = -1;

				}
			}
		}
	

	class philosopher extends Thread {
		
		int num;				//哲学家编号
		boolean isHungry;			//哲学家是否饥饿

	
		public philosopher(int num) {
			this.num = num ;
			}

		public void run() {

			while (true) {
				// isHungry = Math.round(Math.random()*1) == 0 ? false : true;
				// if(isHungry){
				eat();
				// this.sleep(millis)
				// } else {
				/*
				 * try { think(); this.sleep(Math.round(Math.random()*1000)); }
				 * catch (InterruptedException e) { // TODO Auto-generated catch
				 * block e.printStackTrace(); }
				 */
				// }

			}
		}

		public void eat() {
		
			if (num % 2 == 1) {
				P(this,fork[num] );
						System.out.println("哲学家" + num + "拿到左边第" + (num) + "号筷子");
				P(this,fork[(num+1)%5]);
						System.out.println("哲学家" + num + "拿到右边第" + (num+1) % 5 + "号筷子");
				try {
						System.out.println("哲学家" + num + "在吃饭");
						this.sleep(1000);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
				V(this, fork[num]);
						System.out.println("哲学家" + num + "放下左边第" + (num) + "号筷子");
				V(this, fork[(num+1)%5]);
						System.out.println("哲学家" + num + "放下右边第" + (num+1)%5 + "号筷子");
			} else {
				P(this,fork[(num+1)%5]);
						System.out.println("哲学家" + num + "拿到右边第" + (num+1) % 5 + "号筷子");
				P(this,fork[num] );
						System.out.println("哲学家" + num + "拿到左边第" + (num) + "号筷子");

				try {
						System.out.println("哲学家" + num + "在吃饭");
						this.sleep(1000);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				V(this, fork[num]);
						System.out.println("哲学家" + num + "放下左边第" + (num) + "号筷子");
				V(this, fork[(num+1)%5]);
						System.out.println("哲学家" + num + "放下右边第" + (num+1)%5 + "号筷子");

			}

		}

		public void think() {
			System.out.println("哲学家" + num + "在思考");
		}

	}

	

	public void init() {

		for (int i = 0; i < 5; i++) {			//初始化5根筷子
			fork[i] = new Semaphore(1,i);
		}
		for (int i = 0; i < 5; i++) {			//初始化5个哲学家和5个线程标志pw
			p[i] = new philosopher(i);
			pw[i] = -1;
		}
		

		for (int i = 0; i < 5; i++) {
			p[i].start();
		}

	}

	public static void main(String[] args) {

		new philosopherProblem().init();
	}

}

这个里面老是在V操作的时候p[ pw[fork.status] ].notify();出现错误：
Exception in thread "Thread-0" java.lang.IllegalMonitorStateException
at java.lang.Object.notify(Native Method)
at help.philosopherProblem.V(philosopherProblem.java:43)
at help.philosopherProblem$philosopher.eat(philosopherProblem.java:109)
at help.philosopherProblem$philosopher.run(philosopherProblem.java:66)
Exception in thread "Thread-2" java.lang.IllegalMonitorStateException
at java.lang.Object.notify(Native Method)
at help.philosopherProblem.V(philosopherProblem.java:43)
at help.philosopherProblem$philosopher.eat(philosopherProblem.java:111)
at help.philosopherProblem$philosopher.run(philosopherProblem.java:66)



哪个高手可以帮忙一下啊，不胜感激。

[上帝的无名指]

把 notify() 改成join 哲学家0拿到右边第1号筷子 哲学家0拿到左边第0号筷子 哲学家2拿到右边第3号筷子 哲学家0在吃饭 哲学家2拿到左边第2号筷子 哲学家2在吃饭 哲学家2放下左边第2号筷子