# 使用notifyAll完善多线程下的生产者消费者模型 我们先看一下wait()的代码注释：  使当前线程等待，直到另一个线程调用了这个对象的notify()或notifyAll()方法，换句话说，这个方法是执行了wait(0); 当前线程必须拥有该对象的监视器。线程释放此监视器的所有权，并等待另一个线程通过调用notify()或notifyAll()方法，让这个对象监视器上等待的线程被唤醒，然后线程等待，直到它可以重新获得监视器的所有权并恢复执行。 notify()是通知一个线程唤醒，而notifyAll()是会将wait()在同一个monitor的所有线程都会唤醒，而我们之前出现问题就是因为notify是随机的，那么我们现在使用notifyAll试一下： ```java /** * @program: ThreadDemo * @description: 优化多线程下的生产者消费者模型，避免多生产者-多消费者造成的程序假死 * @author: hs96.cn@Gmail.com * @create: 2020-09-07 */ public class ProduceConsumerVersion3 { private int i = 0; private final Object LOCK = new Object(); private volatile boolean isProduced = false; public void produce() { synchronized (LOCK) { if (isProduced) { try { LOCK.wait(); } catch (InterruptedException e) { e.printStackTrace(); } } System.out.println(Thread.currentThread().getName() + "->" + (++i)); LOCK.notifyAll(); isProduced = true; } } public void consume() { synchronized (LOCK) { if (!isProduced) { try { LOCK.wait(); } catch (InterruptedException e) { e.printStackTrace(); } } System.out.println(Thread.currentThread().getName() + "->" + i); LOCK.notifyAll(); isProduced = false; } } public static void main(String[] args) { ProduceConsumerVersion3 pc = new ProduceConsumerVersion3(); Stream.of("P1", "P2", "P3").forEach(n -> new Thread(new Runnable() { @Override public void run() { while (true) { pc.produce(); try { Thread.sleep(10); } catch (InterruptedException e) { e.printStackTrace(); } } } }, n).start()); Stream.of("C1", "C2", "C3", "C4").forEach(n -> new Thread(() -> { while (true) { pc.consume(); try { Thread.sleep(10); } catch (InterruptedException e) { e.printStackTrace(); } } }, n).start()); } } ``` 运行效果如下：  可以看到有连续生产2个的情况，那么是什么原因导致的呢？ 其实仔细想一下，就是p3的生产完之后释放锁，然后p2抢到了，就继续生产了，那么怎么解决呢？让p2wait到p3生产的数据消费掉即可了，改进代码如下：‘ ```java /** * @program: ThreadDemo * @description: 优化多线程下的生产者消费者模型，避免多生产者-多消费者造成的程序假死 * @author: hs96.cn@Gmail.com * @create: 2020-09-07 */ public class ProduceConsumerVersion3 { private int i = 0; private final Object LOCK = new Object(); private volatile boolean isProduced = false; public void produce() { synchronized (LOCK) { while (isProduced) { try { //System.out.println(Thread.currentThread().getName()+"wait...."); LOCK.wait(); } catch (InterruptedException e) { e.printStackTrace(); } } System.out.println(Thread.currentThread().getName() + "->" + (++i)); LOCK.notifyAll(); isProduced = true; } } public void consume() { synchronized (LOCK) { while (!isProduced) { try { //System.out.println(Thread.currentThread().getName()+"wait...."); LOCK.wait(); } catch (InterruptedException e) { e.printStackTrace(); } } System.out.println(Thread.currentThread().getName() + "->" + i); LOCK.notifyAll(); isProduced = false; } } public static void main(String[] args) { ProduceConsumerVersion3 pc = new ProduceConsumerVersion3(); Stream.of("P1", "P2", "P3").forEach(n -> new Thread(new Runnable() { @Override public void run() { while (true) { pc.produce(); try { Thread.sleep(10); } catch (InterruptedException e) { e.printStackTrace(); } } } }, n).start()); Stream.of("C1", "C2", "C3", "C4").forEach(n -> new Thread(() -> { while (true) { pc.consume(); try { Thread.sleep(10); } catch (InterruptedException e) { e.printStackTrace(); } } }, n).start()); } } ``` 运行效果如下：