Java等待线程在通知后不会恢复

Question

我有下面的程序，有 2 个线程 T1 和 T2。 T1 首先运行并进入等待状态。 T2 正在调用通知。为什么 T1 线程不恢复并打印“Thread-0 iswake up”

public class WaitNotifyTest{
    public static void main(String[] args) {
        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                synchronized (this) {
                    System.out.println(Thread.currentThread().getName() + " is running");
                    try {
                        wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName() + " is waken up");
                }
            }
        });
        Thread t2 = new Thread(new Runnable() {
            @Override
            public void run() {
                synchronized (this) {
                    try {
                        Thread.sleep(3000);
                        System.out.println(Thread.currentThread().getName() + " is running");
                        notify();
                        System.out.println(Thread.currentThread().getName() + " notifying");
                    } catch (InterruptedException e1) {
                        e1.printStackTrace();
                    }
                }
            }
        });
        t1.start();
        t2.start();
    }
}

输出为

Thread-0 is running
Thread-1 is running
Thread-1 notifying

请注意，在此输出之后我的程序不会结束/终止。谁能解释一下为什么我的程序没有终止。

Answer 1

您的代码中有两个问题 1.线程之间应该使用同一个对象进行通信。 2.在您已获取锁定的同一对象上调用 wait 并通知。

public class WaitNotifyTest{


    public static void main(String[] args) {
        Object lock=new Object(); 
            Thread t1 = new Thread(new Runnable() {
                @Override
                public void run() {
                    synchronized (lock) {
                        System.out.println(Thread.currentThread().getName() + " is running");
                        try {
                            lock.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        System.out.println(Thread.currentThread().getName() + " is waken up");
                    }
                }
            });
            Thread t2 = new Thread(new Runnable() {
                @Override
                public void run() {
                    synchronized (lock) {
                        try {
                            Thread.sleep(3000);
                            System.out.println(Thread.currentThread().getName() + " is running");
                            lock.notify();
                            System.out.println(Thread.currentThread().getName() + " notifying");
                        } catch (InterruptedException e1) {
                            e1.printStackTrace();
                        }
                    }
                }
            });
            t1.start();
            t2.start();
        }
    }