场景

• 学习

分析

     * @deprecated   This method has been deprecated, as it is
     *   inherently deadlock-prone.  If the target thread holds a lock on the
     *   monitor protecting a critical system resource when it is suspended, no
     *   thread can access this resource until the target thread is resumed. If
     *   the thread that would resume the target thread attempts to lock this
     *   monitor prior to calling <code>resume</code>, deadlock results.  Such
     *   deadlocks typically manifest themselves as "frozen" processes.
     *   For more information, see
     *   <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
     *   are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.

• suspend使线程进入挂起状态，直到resume释放这个线程。但是在这期间，suspend占用的监控器不会释放，如果释放目标线程的线程尝试获取监控器，则死锁。

死锁例子

    public static void main(String[] args) throws InterruptedException {
        Thread thread = new Thread(ResumeAndSuspendDemo::sayHelloWorld);

        thread.start();
        synchronized (ResumeAndSuspendDemo.class) {
            thread.resume();
        }
        System.out.printf("%s is over \n", Thread.currentThread().getName());

    }

    private static void sayHelloWorld()
    {
        Object monitor = ResumeAndSuspendDemo.class;
        synchronized (monitor) {
            try {
                Thread.currentThread().suspend();
                monitor.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.printf("线程[%s] 恢复执行: <==============> Hello World!\n", Thread.currentThread().getName());
        }
    }