也是涉及到多线程的
以下是生产者消费者网上示例
https://blog.csdn.net/antony9118/article/details/51481884

为什么 java wait/notify 必须与 synchronized 一起使用，jvm究竟做了些什么

/**
 * @author jy
 * @date 2018年5月15日
 * <p>Description: </p> 
 */
package com.threadtest;

import java.util.Queue;

/**
 * @author jy
 *
 */
public class Producer implements Runnable{

    final Queue queue;
    
    public Producer(Queue queue) {
        super();
        this.queue = queue;
    }


    /* (non-Javadoc)
     * @see java.lang.Runnable#run()
     */
    @Override
    public void run() {
        synchronized(queue){
            for(int i=0;i<4;i++){
                if(queue.size()>=1){
                    try {
                        queue.wait();
                        System.out.println("queue is full");
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    queue.add(i);
                    System.out.println("produce"+i);
                    queue.notify();
                }
            }
        }
    
    }
}

/**
 * @author jy
 * @date 2018年5月15日
 * <p>Description: </p> 
 */
package com.threadtest;

import java.util.LinkedList;
import java.util.Queue;

/**
 * @author jy
 *
 */
public class Consumer implements Runnable {
    final Queue queue;

    public Consumer(Queue queue) {
        super();
        this.queue = queue;
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.lang.Runnable#run()
     */
    @Override
    public void run() {
        while (true) {
            synchronized (queue) {
                while (queue.size() == 0) {
                    System.out.println("queque is empty");
                    try {
                        queue.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                int num = (int) queue.poll();
                System.out.println("consume" + num);

                
                queue.notify();
                if (num == 3) {
                    break;
                }
            }

        }

    }

    public static void main(String args[]) {
        Queue queue = new LinkedList();
        Producer pro = new Producer(queue);
        Consumer consumer = new Consumer(queue);
        Thread t1 = new Thread(pro, "pro");
        t1.start();
        Thread t2 = new Thread(consumer, "con");
        t2.start();
    }

}