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Commit ca059a5

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更新线程通信
1 parent a5f392d commit ca059a5

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package com.javaedge.concurrency.common.communication;
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import java.util.concurrent.locks.LockSupport;
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import org.testng.annotations.Test;
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/**
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* 三种线程协作通信的方式:suspend/resume、wait/notify、park/unpark
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*
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* @author JavaEdge
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* @date 2019年10月8日
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*/
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public class ThreadCommunication {
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/**
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* 包子店
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*/
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public static Object bunShop = null;
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/**
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* 正常的suspend/resume
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*/
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@Test
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public void suspendResumeTest() throws Exception {
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// 启动线程
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Thread consumerThread = new Thread(() -> {
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if (bunShop == null) {
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// 没包子,则进入等待
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System.out.println("1、进入等待");
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Thread.currentThread().suspend();
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}
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System.out.println("2、买到包子,回家");
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});
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consumerThread.start();
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// 3秒之后,生产一个包子
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Thread.sleep(3000L);
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bunShop = new Object();
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consumerThread.resume();
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System.out.println("3、通知消费者");
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}
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/**
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* 死锁的suspend/resume。 suspend并不会像wait一样释放锁,容易写出死锁代码
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*/
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@Test
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public void suspendResumeDeadLockTest() throws Exception {
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// 启动线程
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Thread consumerThread = new Thread(() -> {
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if (bunShop == null) {
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// 没包子,则进入等待
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System.out.println("1、进入等待");
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// 当前线程拿到锁,然后挂起
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synchronized (this) {
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Thread.currentThread().suspend();
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}
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}
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System.out.println("2、买到包子,回家");
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});
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consumerThread.start();
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// 3秒之后,生产一个包子
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Thread.sleep(3000L);
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bunShop = new Object();
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// 争取到锁以后,再恢复consumerThread
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synchronized (this) {
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consumerThread.resume();
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}
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System.out.println("3、通知消费者");
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}
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/**
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* 导致程序永久挂起的suspend/resume
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*/
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@Test
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public void suspendResumeDeadLockTest2() throws Exception {
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// 启动线程
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Thread consumerThread = new Thread(() -> {
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if (bunShop == null) {
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System.out.println("1、没包子,进入等待");
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try { // 为这个线程加上一点延时
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Thread.sleep(5000L);
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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// 这里的挂起执行在resume后面
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Thread.currentThread().suspend();
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}
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System.out.println("2、买到包子,回家");
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});
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consumerThread.start();
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// 3秒之后,生产一个包子
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Thread.sleep(3000L);
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bunShop = new Object();
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consumerThread.resume();
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System.out.println("3、通知消费者");
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consumerThread.join();
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}
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/**
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* 正常的wait/notify
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*/
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@Test
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public void waitNotifyTest() throws Exception {
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// 启动消费者线程
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new Thread(() -> {
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if (bunShop == null) {
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// 如果没包子,则进入等待
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synchronized (this) {
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try {
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System.out.println("1、进入等待");
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this.wait();
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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}
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}
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System.out.println("2、买到包子,回家");
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}).start();
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// 3秒之后,生产一个包子
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Thread.sleep(3000L);
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bunShop = new Object();
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synchronized (this) {
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this.notifyAll();
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System.out.println("3、通知消费者");
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}
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}
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/**
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* 会导致程序永久等待的wait/notify
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*/
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@Test
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public void waitNotifyDeadLockTest() throws Exception {
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// 启动线程
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new Thread(() -> {
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if (bunShop == null) { // 如果没包子,则进入等待
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try {
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Thread.sleep(5000L);
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} catch (InterruptedException e1) {
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e1.printStackTrace();
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}
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synchronized (this) {
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try {
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System.out.println("1、进入等待");
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this.wait();
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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}
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}
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System.out.println("2、买到包子,回家");
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}).start();
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// 3秒之后,生产一个包子
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Thread.sleep(3000L);
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bunShop = new Object();
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synchronized (this) {
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this.notifyAll();
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System.out.println("3、通知消费者");
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}
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}
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/**
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* 正常的park/unpark
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*/
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@Test
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public void parkUnparkTest() throws Exception {
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// 启动线程
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Thread consumerThread = new Thread(() -> {
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if (bunShop == null) { // 如果没包子,则进入等待
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System.out.println("1、进入等待");
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LockSupport.park();
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}
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System.out.println("2、买到包子,回家");
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});
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consumerThread.start();
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// 3秒之后,生产一个包子
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Thread.sleep(3000L);
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bunShop = new Object();
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LockSupport.unpark(consumerThread);
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System.out.println("3、通知消费者");
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}
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/**
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* 死锁的park/unpark
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*/
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@Test
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public void parkUnparkDeadLockTest() throws Exception {
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// 启动线程
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Thread consumerThread = new Thread(() -> {
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if (bunShop == null) { // 如果没包子,则进入等待
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System.out.println("1、进入等待");
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// 当前线程拿到锁,然后挂起
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synchronized (this) {
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LockSupport.park();
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}
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}
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System.out.println("2、买到包子,回家");
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});
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consumerThread.start();
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// 3秒之后,生产一个包子
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Thread.sleep(3000L);
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bunShop = new Object();
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// 争取到锁以后,再恢复consumerThread
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synchronized (this) {
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LockSupport.unpark(consumerThread);
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}
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System.out.println("3、通知消费者");
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}
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public static void main(String[] args) throws Exception {
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// 对调用顺序有要求,也要开发自己注意锁的释放。这个被弃用的API, 容易死锁,也容易导致永久挂起。
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// new Demo6().suspendResumeTest();
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// new Demo6().suspendResumeDeadLockTest();
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// new Demo6().suspendResumeDeadLockTest2();
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// wait/notify要求再同步关键字里面使用,免去了死锁的困扰,但是一定要先调用wait,再调用notify,否则永久等待了
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// new Demo6().waitNotifyTest();
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// new Demo6().waitNotifyDeadLockTest();
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// park/unpark没有顺序要求,但是park并不会释放锁,所有再同步代码中使用要注意
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// new Demo6().parkUnparkTest();
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// new Demo6().parkUnparkDeadLockTest();
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}
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}

‎pom.xml

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<artifactId>spring-rabbit</artifactId>
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<version>2.1.4.RELEASE</version>
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</dependency>
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-test</artifactId>
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</dependency>
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<dependency>
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<groupId>org.testng</groupId>
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<artifactId>testng</artifactId>
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<version>7.0.0-beta3</version>
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<scope>compile</scope>
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</dependency>
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</dependencies>
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