前言
wait()和notfiy()方法被定义在Object对象中用来线程间的通信。由于每个对象都可以作为锁，所以这些方法被定义在了Object类而不是Thread类中。借由下面消费者/生产者的例子，可以更好地理解线程间的synchronized和沟通机制。
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
public class NotifyAndWaitTest {
private static Executor executor = Executors.newFixedThreadPool(6);
private static boolean hasGoods = false;
/**
* 1. 每次wait的时候线程会释放synchronized中的锁和资源
* 2. sleep()不会释放锁，但是会释放资源让别的线程执行
*/
public static void main(String[] args) {
NotifyAndWaitTest producerLock = new NotifyAndWaitTest();
Runnable consumer = () -> {
System.out.println(getCurrentThreadNumbr() + "号消费者启动了");
while (true) {
synchronized (producerLock) {
System.out.println(getCurrentThreadNumbr() + "号消费者获得了锁");
while (!hasGoods) {
try {
System.out.println(getCurrentThreadNumbr() + "号消费者在等待并释放了锁");
producerLock.wait();
System.out.println(getCurrentThreadNumbr() + "号消费者被唤醒了");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
//有东西的时候去消费
System.out.println(getCurrentThreadNumbr() + "号消费者成功了，哈哈");
hasGoods = false;
//使用notify去”碰运气“式地唤醒生产者，大多数时间生产者只会生产一次
//但是偶尔可以看到同一个消费者和生产者之间频繁互动的情况
producerLock.notify();
}
}
};
Runnable producer = () -> {
System.out.println(getCurrentThreadNumbr() + "--生产者启动了");
while (true) {
synchronized (producerLock) {
System.out.println(getCurrentThreadNumbr() + "--生产者获得了锁");
while (hasGoods) {
try {
System.out.println(getCurrentThreadNumbr() + "--生产者在等待并释放了锁");
producerLock.wait();
System.out.println(getCurrentThreadNumbr() + "--生产者被唤醒了");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println(getCurrentThreadNumbr() + "--生产了一个？哈哈");
hasGoods = true;
producerLock.notify();
}
}
};
executor.execute(consumer);
executor.execute(consumer);
executor.execute(producer);
executor.execute(consumer);
executor.execute(consumer);
executor.execute(consumer);
}
private static String getCurrentThreadNumbr() {
return Thread.currentThread().getName().split("-")[3];
}
}