线程通信wait与notify

今天药忘吃喽~ 2022-05-14 02:53 261阅读 0赞

### Wait/notify ###

可以实现线程间的通信

Wait方法，释放锁  
Notify方法，不释放锁

Wait与notify方法  
必须配置synchronize使用

package com.bjsxt.base.conn008;
    
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Queue;
    import java.util.concurrent.CountDownLatch;
    import java.util.concurrent.LinkedBlockingDeque;
    import java.util.concurrent.LinkedBlockingQueue;
    
    /** * wait notfiy 方法，wait释放锁，notfiy不释放锁 * */
    public class ListAdd2 { 
        private volatile static List list = new ArrayList();
    
        public void add() {
            list.add("bjsxt");
        }
    
        public int size() {
            return list.size();
        }
    
        public static void main(String[] args) {
    
            final ListAdd2 list2 = new ListAdd2();
    
            // 1 实例化出来一个 lock
            // 当使用wait 和 notify 的时候 ， 一定要配合着synchronized关键字去使用
            final Object lock = new Object();
    
            final CountDownLatch countDownLatch = new CountDownLatch(1);
    
            Thread t1 = new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        synchronized (lock) {
                            for (int i = 0; i < 10; i++) {
                                list2.add();
                                System.out.println("当前线程：" + Thread.currentThread().getName() + "添加了一个元素..");
                                Thread.sleep(500);
                                if (list2.size() == 5) {
                                    System.out.println("已经发出通知..");
                                    countDownLatch.countDown();
                                    lock.notify();
                                }
                            }
                        }
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
    
                }
            }, "t1");
    
            Thread t2 = new Thread(new Runnable() {
                @Override
                public void run() {
                    synchronized (lock) {
                        if (list2.size() != 5) {
                            try {
                                System.out.println("t2进入...");
                                lock.wait();
                                countDownLatch.await();
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                        }
                        System.out.println("当前线程：" + Thread.currentThread().getName() + "收到通知线程停止..");
                        throw new RuntimeException();
                    }
                }
            }, "t2");
    
            t2.start();
            t1.start();
    
        }
    
    }

运行  
![这里写图片描述][70]

线程t2执行，wait释放锁  
线程t1执行，notify并没有是释放锁

等待线程t1，执行完毕  
跳出synchronize代码块，线程t2才会执行

[70]: /images/20220514/e68f318de7e24a3db60ad55f1e68f46a.png