Java 线程挂起不起作用

Question

这是一个使用java线程的示例代码。问题是我无法暂停线程。

public class RunnableDemo implements Runnable {
   public Thread t;
   private String threadName;
   boolean suspended = false;
   RunnableDemo( String name){
       threadName = name;
       System.out.println("Creating " +  threadName );
   }
   public void run() {
      System.out.println("Running " +  threadName );
      try {
         while (true) {
            System.out.println("Thread: " + threadName + ", " + i);
            // Let the thread sleep for a while.
            Thread.sleep(300);
            synchronized(this) {
               while(suspended) {
                  wait();
               }
            }
        }
     } catch (InterruptedException e) {
         System.out.println("Thread " +  threadName + " interrupted.");
     }
     System.out.println("Thread " +  threadName + " exiting.");
   }
   public void start ()
   {
      System.out.println("Starting " +  threadName );
      if (t == null)
      {
         t = new Thread (this, threadName);
         t.start ();
      }
   }
   public void suspend() {
      suspended = true;
   }

下面的挂起函数不起作用:

RunnableDemo R1 = new RunnableDemo( "Thread-1");
R1.start();
R1.suspend();  // This line does not work and thread continues ...

事实上，当我调用 suspend() 时，线程看不到 suspended 的新值。有什么想法吗？

Answer 1

将suspended声明为volatile :

volatile boolean suspended = false;