Java - 无法通知等待线程？

Question

System.out.println("Thread state: " + threads[i].getState());
threads[i].notify();

产生以下输出:

Thread state: WAITING
Exception in thread "Thread-1" java.lang.IllegalMonitorStateException
at java.lang.Object.notify(Native Method)
at MyPakc.An.run(An.java:49)
at java.lang.Thread.run(Thread.java:679)

这是怎么回事？为什么我无法通知 hibernate 线程？

编辑:threads[]类的代码:

package Part2;

import java.util.List;
import javax.swing.JPanel;



class BThread extends Thread{
    private boolean completedThisIter = false;

    @Override
    public synchronized void run() {
        while (true) {
            completedThisIter = false;
            doStuff()
            System.out.println("Completed iter");
            completedThisIter = true;
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public boolean getCompletedThisIter() {
        return completedThisIter;
    }
}

编辑:这是调用此函数的代码

public synchronized void run(){
// OTHER STUFF
    for (int iter = 0; iter < 1212; ++iter){
        System.out.println("Iter " + iter);
        lastAssignedBallIndex = -1;
        for (int i = 0; i < numThreads; i++) {
            //System.out.println("Num " + numThreads + "  " + i);
            //ballThreads[i] = new BallThread(ballList.subList(lastAssignedBallIndex+1,lastAssignedBallIndex+numBallsPerThread),
            //        ballPanel);
            //lastAssignedBallIndex += numBallsPerThread;
            System.out.println("State " + ballThreads[i].getState());
            if (ballThreads[i].getState() == Thread.State.NEW) {
                ballThreads[i].start();
            } else { //if (ballThreads[i].getState() == Thread.State.BLOCKED) {
                System.out.println("Thread state: " + ballThreads[i].getState());
                ballThreads[i].notify();
            }
        }
        //try{
            for (int i = 0; i < numThreads; i++) {
                while (!ballThreads[i].getCompletedThisIter()) {
                    System.out.println("iter:" + iter + " ball:" + i + "  " + ballThreads[i].getCompletedThisIter());
                    //wait(); // TODO elliminate polling here
                }
            }
            System.out.println("Joined");
        //}
       // catch(InterruptedException ie){ie.printStackTrace();}


        ballPanel.repaint();
        notifyAll();
        try{
            Thread.sleep(2);
        }
        catch (InterruptedException ie){}
    }
}

Answer 1

您正在打印 ballThreads[i] 的状态，然后通知 threads[i]。不确定这是否是预期的行为，但当您不拥有对象的监视器时，不允许您通知线程。您确定要在 threads[i] 对象的 synchronized() block 内调用此函数吗？

<小时/>

编辑:

Yes, the method that this code is taken out of is synchronized

编辑问题后，同步位于方法上，而不是对象的监视器上，您需要将代码放在如下所示的 block 中:

synchronized(threads[i]) {
    // some stuff
    threads[i].notify();
}

这里重要的一点(与方法声明中的 synchronized 关键字相反)是在对象上同步，然后在该 block 内调用 notify() 在对象上。示例:

public void run()
{
    synchronized(myObject) {
        // do some stuff
        myObject.notify();
    }
}

或

public void run()
{
    synchronized(thread1) {
        // do some stuff
        thread1.notify();
    }
}

或

public void run()
{
    synchronized(syncObject) {
        // do some stuff
        syncObject.notify();
    }
}

看到图案了吗？更多信息请点击:http://docs.oracle.com/javase/tutorial/essential/concurrency/locksync.html