为什么thread.stop()不起作用？

Question

我刚从sun的文档中了解到,当我调用thread.stop()方法时,run()方法将在ThreadDeath错误被抛出时终止,并且还释放此线程持有的所有锁,如何证明它？

我尝试了我的测试程序,如下所示:

    public static void main(String[] args) {
  final Object lock = new Object();
  try {
   Thread t = new Thread() {
    public synchronized void run() {
     try {
      synchronized (lock) {
       long start = System.currentTimeMillis();
       for (int i = 0; i < 10000; i++)
        System.out.println("runing.." + i);
       System.out
         .println((System.currentTimeMillis() - start) / 1000);
      }

     } catch (Throwable ex) {
      System.out.println("Caught in run: " + ex);
      ex.printStackTrace();
     }
    }
   };

   t.start();
   // Give t time to get going...
   Thread.sleep(100);
   t.stop(); // EXPECT COMPILER WARNING
  } catch (Throwable t) {
   System.out.println("Caught in main: " + t);
   t.printStackTrace();
  }

 }

只有当我在run()方法中放入wait()时,我才能捕获ThreadDeath错误,有没有人知道jvm如何处理stop()的细节？

    public static void main(String[] args) {
  final Object lock = new Object();
  try {
   Thread t = new Thread() {
    public synchronized void run() {
     try {
      synchronized (lock) {
       wait();
       long start = System.currentTimeMillis();
       for (int i = 0; i < 10000; i++)
        System.out.println("runing.." + i);
       System.out
         .println((System.currentTimeMillis() - start) / 1000);

      }

     } catch (Throwable ex) {
      System.out.println("Caught in run: " + ex);
      ex.printStackTrace();
     }
    }
   };

   t.start();
   // Give t time to get going...
   Thread.sleep(100);
   t.stop(); // EXPECT COMPILER WARNING
  } catch (Throwable t) {
   System.out.println("Caught in main: " + t);
   t.printStackTrace();
  }

 }

Answer 1

简单的答案是jvm没有可靠的方法来阻止线程.要停止或中断线程,目标线程需要通过进入某些可中断状态(例如sleep()或wait())进行协作.

由于这个原因,不推荐使用Thread.stop()方法(其中包括).有关详细信息,请参阅http://download.oracle.com/javase/1.4.2/docs/guide/misc/threadPrimitiveDeprecation.html.