多線程producer&customer

package com.phj20110824.bread;


class  Warehouse {
	private static int num = 0;

	public synchronized void product() {
		while (this.getNum() == 2) {			
			try {
				wait();
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		num++;
		System.out.println(this.getNum());
		notify();
		
	}

	public synchronized void customer() {
		while (this.getNum() == 1) {
			
			try {
				wait();
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}	
		num--;
		System.out.println(this.getNum());
		notify();
		
	}

	public int getNum() {
		return this.num;
	}
}

class ProduceThread implements Runnable {
	private  Warehouse warehouse;

	public ProduceThread(Warehouse warehouse) {
		this.warehouse = warehouse;
	}

	@Override
	public void run() {
		// TODO Auto-generated method stub
		for (int i = 0; i < 20; i++) {
			warehouse.product();
		}

	}
}

class CustomerThread implements Runnable {
	private Warehouse warehouse;

	public CustomerThread(Warehouse warehouse) {
		this.warehouse = warehouse;
	}

	@Override
	public void run() {
		// TODO Auto-generated method stub
		for (int i = 0; i < 20; i++) {
			warehouse.customer();
		}
	}
}

public class ProduceCustomerDemo {
	public static void main(String[] args) {
		Warehouse warehouse = new Warehouse();		
		new Thread(new ProduceThread(warehouse)).start();		
		 new Thread(new CustomerThread(warehouse)).start(); 
		 new Thread(new ProduceThread(warehouse)).start(); 
		 new Thread(new CustomerThread(warehouse)).start(); 
		 new Thread(new ProduceThread(warehouse)).start();
		 new Thread(new CustomerThread(warehouse)).start();
	}
}