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前言

题目：一个初始值为零的变量，多个线程对其交替操作，分别加1减1

实现步骤：

1. 线程操作资源类
2. 判断，干活，通知
3. 防止虚假唤醒机制，即：多线程的判断需要用 while，不能使用 if（jdk 要求的，保证线程不会出错）

传统派

加锁实现，通过加锁保证线程的安全

class ShareData {// 资源类private int number = 0;// 锁private final Lock lock = new ReentrantLock();private final Condition condition = lock.newCondition();public void increment() throws InterruptedException {lock.lock();try {// 1. 判断，不能使用 if
//            if (number != 0) {while (number != 0) {// 有值，等待消费，不能生产condition.await();}// 2. 干活number++;System.out.println(Thread.currentThread().getName() + "\t" + number);// 3. 通知，唤醒condition.signalAll();} catch (InterruptedException e) {e.printStackTrace();} finally {// 手动解锁lock.unlock();}}public void decrement() {lock.lock();try {// 1. 判断
//            if (number == 0) {while (number == 0) {// 有值，等待消费，不能生产condition.await();}// 2. 干活number--;System.out.println(Thread.currentThread().getName() + "\t" + number);// 3. 通知，唤醒condition.signalAll();} catch (InterruptedException e) {e.printStackTrace();} finally {lock.unlock();}}
}public class Test {public static void main(String[] args) throws Exception {// 传统ShareData shareData = new ShareData();new Thread(() -> {for (int i = 1; i <= 5; i++) {try {shareData.increment();} catch (InterruptedException e) {e.printStackTrace();}}}, "Produce0").start();new Thread(() -> {for (int i = 1; i <= 5; i++) {shareData.decrement();}}, "Consume0").start();// 多个线程验证性质 3// 发现不是生产一个就消费一个了new Thread(() -> {for (int i = 1; i <= 5; i++) {try {shareData.increment();} catch (InterruptedException e) {e.printStackTrace();}}}, "Produce1").start();new Thread(() -> {for (int i = 1; i <= 5; i++) {shareData.decrement();}}, "Consume2").start();}
}

输出结果：

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维新派

使用阻塞队列和原子类实现

class MyResource {// 默认开启private volatile boolean FLAG = true;// 原子类作为共享变量private final AtomicInteger atomicInteger = new AtomicInteger();// 阻塞队列实现锁的功能BlockingQueue<String> blockingQueue = null;public MyResource(BlockingQueue<String> blockingQueue) {this.blockingQueue = blockingQueue;}public void myProd() throws InterruptedException {String date = null;boolean retValue;while (FLAG) {date = atomicInteger.incrementAndGet() + "";retValue =  blockingQueue.offer(date, 2L, TimeUnit.SECONDS);if (retValue) {System.out.println(Thread.currentThread().getName() + "\t插入队列" + date + "成功");} else {System.out.println(Thread.currentThread().getName() + "\t插入队列" + date + "失败");}// 一秒生产一个TimeUnit.SECONDS.sleep(1);}System.out.println(Thread.currentThread().getName() + "\t停止生产");}public void myConsumer() throws InterruptedException {String result = null;while (FLAG) {result = blockingQueue.poll(2L, TimeUnit.SECONDS);if (result == null || result.equalsIgnoreCase("")) {FLAG = false;System.out.println(Thread.currentThread().getName() + "\t超过两秒没有取到，退出");System.out.println();System.out.println();return;}System.out.println(Thread.currentThread().getName() + "\t消费队列" + result + "成功");}}public void stop() {this.FLAG = false;}
}public class Test {public static void main(String[] args) throws Exception {MyResource myResource = new MyResource(new ArrayBlockingQueue<>(10));new Thread(() -> {System.out.println(Thread.currentThread().getName() + "\t生产线程启动");try {myResource.myProd();} catch (InterruptedException e) {e.printStackTrace();}}, "Prod").start();new Thread(() -> {System.out.println(Thread.currentThread().getName() + "\t消费线程启动");try {myResource.myConsumer();System.out.println();System.out.println();} catch (InterruptedException e) {e.printStackTrace();}}, "Consumer").start();Thread.sleep(5000);System.out.println();System.out.println("时间到，main 线程叫停");myResource.stop();}
}

输出结果：