Java wait notify 的使用场景——凤凰网面试

今天去凤凰网面试了，可惜自己准备的东西都没有面到，有些紧张，其间有问到一个wait，notify的使用场景，答曰：生产者与消费者模式，当时只写了个大概，现在将代码贴出。

储存柜

package cuspro;

import java.util.ArrayList;
import java.util.List;

public class Storage {
	private List<Object> foods;
	
	public final static int MAX_SIZE = 5;
	
	public Storage(){
		foods = new ArrayList<Object>();
	}
	public List<Object> getFoods() {
		return foods;
	}

	public void setFoods(List<Object> foods) {
		this.foods = foods;
	}
	
	
}

 运行类，内部有：生产者，消费者两个内部类实现了Runnable接口：

package cuspro;

public class Company {
	public static void main(String[] args) {
		Company c = new Company();
		Object lock = new Object();
		Storage storage = new Storage();
		try {
			Thread.sleep(1000);
		} catch (InterruptedException e1) {
			e1.printStackTrace();
		}
		new Thread(c.new Customer(storage, lock)).start();
		new Thread(c.new Producer(storage, lock)).start();
		new Thread(c.new Customer(storage, lock)).start();
		new Thread(c.new Producer(storage, lock)).start();
		new Thread(c.new Customer(storage, lock)).start();
		new Thread(c.new Producer(storage, lock)).start();
		new Thread(c.new Customer(storage, lock)).start();
		new Thread(c.new Producer(storage, lock)).start();
		new Thread(c.new Customer(storage, lock)).start();
		new Thread(c.new Producer(storage, lock)).start();
		new Thread(c.new Customer(storage, lock)).start();
		new Thread(c.new Producer(storage, lock)).start();

	}

	/**
	 * 消费者
	 * 
	 * @author xtuali
	 * 
	 */
	private class Customer implements Runnable {
		private Storage storage;

		private Object lock;


		public Customer(Storage storage, Object lock) {
			super();
			this.storage = storage;
			this.lock = lock;
		}

		public void run() {
			while (true) {
				try {
					Thread.sleep(1000);
				} catch (InterruptedException e1) {
					e1.printStackTrace();
				}
				synchronized (lock) {
					while (storage.getFoods().size() <= 0) {
						try {
							System.out.println("货物已空，提示生产者生产");
							
							lock.wait();   //当前线程在lock上等待，并释放锁
						} catch (InterruptedException e) {
							e.printStackTrace();
						}
					}
					storage.getFoods().remove(0);
					lock.notifyAll(); //唤醒消费者与生产者
					System.out.println("消费者消费1, "+Thread.currentThread().getName()+", 余量："+storage.getFoods().size());
				}
			}
		}
	}

	/**
	 * 生产者
	 * 
	 * @author xtuali
	 * 
	 */
	private class Producer implements Runnable {
		private Storage storage;

		private Object lock;
		

		public Producer(Storage storage, Object lock) {
			super();
			this.storage = storage;
			this.lock = lock;
		}

		public void run() {
			while (true) {
				try {
					Thread.sleep(1000);
				} catch (InterruptedException e1) {
					e1.printStackTrace();
				}
				synchronized (lock) {
					while (storage.getFoods().size() >= Storage.MAX_SIZE) {
						try {
							System.out.println("货物已满，提示消费者消费");
							
							lock.wait(); //当前线程在lock上等待，并释放锁
						} catch (InterruptedException e) {
							e.printStackTrace();
						}
					}
					storage.getFoods().add(1);
					lock.notifyAll();  //唤醒消费者与生产者
					System.out.println("生产者生产1, "+Thread.currentThread().getName() +",余量："+storage.getFoods().size());
				}
			}
		}
	}
}

 之前考虑在Customer与Producer内部申明两个lock，一个是用来与Producer线程来通信，一个是用来与Customer线程来通信，但是锁没法释放，所以就只用了一个lock，但是这一个lock也解决了问题了！