为什么弃用了Thread.suspend Thread.resume方法

Myth丶恋晨 2022-12-31 06:19 252阅读 0赞

### 文章目录 ###

*   *   *  场景
         *  分析
         *  死锁例子

### 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());
            }
        }