Question

import java.math.BigInteger;

class Numbers {

    final static int NUMBER = 2;
    final static int POWER = 4;

    static long msecs;
    static BigInteger result;
    static Boolean done = false;

    public static void main(String[] args) {

        BigInteger number = BigInteger.valueOf(NUMBER);
        result = number;

        //Boolean done = false;

        Runnable pow = () -> {
            System.out.println(number + " pow " + POWER + " = " + number.pow(POWER));

            synchronized (done) {
                done = true;
                done.notifyAll();
            }
        };

        Runnable sum = () -> {
            for(int i = 2; i<POWER; i=i*i) {
                result = result.multiply(result);
            }

            System.out.println(number + " sum " + POWER + " = " + result);

            synchronized (done) {
                done = true;
                done.notifyAll();
            }
        };

        Runnable time = () -> {
            for(msecs = 0; true; msecs++) {
                try {
                    Thread.sleep(1);
                } catch(InterruptedException e) {
                    //nic
                }
            }
        };

        Thread timet = new Thread(time);
        Thread sumt = new Thread(sum);
        Thread powt = new Thread(pow);

        timet.start();
        powt.start();

        synchronized (done) {
            while(!done) {
                try {
                    done.wait();
                } catch (InterruptedException e) {
                    //nic
                }
            }
        }

        timet.interrupt();
        powt.interrupt();

        System.out.println("Pow time " + msecs + " msecs.");
        done = false;

        timet.start();
        sumt.start();

        try {
            synchronized (done) {
                while (!done) {
                    done.wait();
                }
            }
        } catch (InterruptedException e) {
            //nic
        }


        timet.interrupt();
        sumt.interrupt();

        System.out.println("Sum time " + msecs + " msecs.");

    }
}

我想检查这两种方法之间的时差，但done.notifyAll()不断抛出IllegalMonitorStateException。

Answer 1

问题出在这里：

image_params

由于您要为synchronized (done) { done = true;//<---problem done.notifyAll(); }分配新值，这意味着您正在done上执行notifyAll，但您的同步块正在使用Boolean.TRUE的监视器。由于Boolean.FALSE要求线程拥有执行它的对象的监视器，因此它会抛出notifyAll。

因此，请勿更改同步对象的值。同时避免在可用于所有类（公共常量/文字）的对象上进行同步，因为您冒着其他人会有相同想法的风险，并且还会在同步中使用它们，这可能会让您感到痛苦。

锁只能从类中属于它们才能访问。以Jon Skeet（What is the difference between synchronized on lockObject and using this as the lock?）为例，并在您自己的同步

IllegalMonitorStateException

Answer 2

我想我知道发生了什么......如果您阅读了Object的关于Object.notifyAll（）的文档

IllegalArgumentException - if the value of timeout is negative. IllegalMonitorStateException - if the current thread is not the owner of the object's monitor. InterruptedException - if any thread interrupted the current thread before or while the current thread was waiting for a notification. The interrupted status of the current thread is cleared when this exception is thrown.

因此，我认为你需要一个新的Object作为锁来访问你的完成。例如：a private final Object doneLock = new Object()。您现在可以在Done上进行同步，而不是在doneLock上进行同步。我应该是最终的，因为锁需要是私人的和最终的，所以他们无法在外面访问。

例如，

synchronize(doneLock) {
    done = true;
    doneLock.notifyAll();
}

NotifyAll，IllegalMonitorStateException

2 个答案: