我没有看到以下代码如何产生看似违反对象锁定义的输出.当然只允许一个线程打印“获取锁定”消息,但他们都这样做？

class InterruptThreadGroup {
    public static void main(String[] args) {
        Object lock = new Object();
        MyThread mt1 = new MyThread(lock);
        MyThread mt2 = new MyThread(lock);
        mt1.setName("A");
        mt1.start();
        mt2.setName("B");
        mt2.start();
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
        }
        // Thread.currentThread().getThreadGroup().interrupt();
    }
}

class MyThread extends Thread {
    private Object lock;

    public MyThread(Object l) {
        this.lock = l;

    }

    public void run() {
        synchronized (lock) {
            System.out.println(getName() + " acquired lock");
            try {
                lock.wait();
            } catch (InterruptedException e) {
                System.out.println(getName() + " interrupted.");
            }
            System.out.println(getName() + " terminating.");
        }
    }
}

解决方法:

这是因为对lock.wait()的调用释放了锁,允许第二个线程进入synchronized块.摘自javadoc

The thread releases ownership of this monitor and waits until another thread notifies threads waiting on this object’s monitor to wake up either through a call to the notify method or the notifyAll method. The thread then waits until it can re-obtain ownership of the monitor and resumes execution.

请注意,您的代码中存在一些问题,例如：

>你不应该在while循环之外等待
>任何地方都没有通知,所以你的等待可以永远持续下去
>让任务实现Runnable并将其作为参数传递给Thread的构造函数而不是直接扩展Thread是一种更好的做法.