notifyAll（）方法上的java.lang.IllegalMonitorStateException

Question

在oracle網站的Java教程之后，我仍在學習Threads。

關於wait（）和notifyAll（），我已經寫了一些代碼。 我的預期輸出是將run（）中的消息打印10次，並在guardedJoy(GuardedBlock guardedBlock)方法中將“ joy”設置為false時，在guardedJoy(GuardedBlock guardedBlock)方法中顯示“ Fun stopFun StopFun Thread停止”消息。

這是我的代碼。

public class GuardedBlock {

private boolean joy = true;

public synchronized void guardedJoy(GuardedBlock guardedBlock) {

    System.out.println(Thread.currentThread().getName() + " Guard Joy method started");
    while (guardedBlock.joy) {
        try {
            System.out.println(Thread.currentThread().getName() + " Going to waiting state");
            guardedBlock.wait();
        } catch (InterruptedException ex) {
        }
    }
    System.out.println("Fun stopped by StopFun Thread");
}

private static class StopFun implements Runnable {

    private GuardedBlock guardedBlock;

    public StopFun(GuardedBlock guardedBlock) {
        this.guardedBlock = guardedBlock;
    }

    @Override
    public void run() {

        for (int x = 0; x < 100; x++) {
            try {
                Thread.sleep(500);
                System.out.println("Allowing fun since its only " + x + " times - " + Thread.currentThread().getName());

                if (x == 10) {
                    guardedBlock.joy = false;
                    guardedBlock.notifyAll();
                    break;
                }
            } catch (InterruptedException ex) {
            }
        }
    }
}

public static void main(String[] args) {

    GuardedBlock guardedBlock = new GuardedBlock();

    StopFun sf = new StopFun(guardedBlock);
    Thread stopFun = new Thread(sf);
    stopFun.start();

    guardedBlock.guardedJoy(guardedBlock);
    }
}

run方法中的代碼可以正常運行，但之后會引發類似這樣的異常。

Exception in thread "Thread-0" java.lang.IllegalMonitorStateException
    at java.lang.Object.notifyAll(Native Method)
    at Synchronization.GuardedBlock$StopFun.run(GuardedBlock.java:38)
    at java.lang.Thread.run(Thread.java:748)

我通過對夫婦的喜歡的網站的問題和答案去這個和這個 ，但無法弄清楚究竟我做錯了。 幫助非常有價值。

謝謝。

Answer 1

必須在synchronized塊中調用wait()和notify() / notifyAll() 。

synchronized (guardedBlock) {
    guardedBlock.notifyAll();
}

等等。