如何在没有 IllegalMonitorStateException 的情况下在 Java 中使用等待和通知? [英] How to use wait and notify in Java without IllegalMonitorStateException?

问题描述

我有 2 个矩阵，我需要将它们相乘，然后打印每个单元格的结果.只要一个单元格准备好，我就需要打印它，但例如，即使 [2][0] 的结果首先准备好，我也需要在单元格 [2][0] 之前打印 [0][0] 单元格.所以我需要按订单打印.所以我的想法是让打印机线程等待，直到 multiplyThread 通知它正确的单元格已准备好打印，然后 printerThread 将打印单元格并返回等等等等..

I have 2 matrices and I need to multiply them and then print the results of each cell. As soon as one cell is ready I need to print it, but for example I need to print the [0][0] cell before cell [2][0] even if the result of [2][0] is ready first. So I need to print it by order. So my idea is to make the printer thread wait until the multiplyThread notifies it that the correct cell is ready to be printed and then the printerThread will print the cell and go back to waiting and so on..

所以我有一个做乘法的线程:

So I have this thread that does the multiplication:

public void run() 
{
    int countNumOfActions = 0; // How many multiplications have we done
    int maxActions = randomize(); // Maximum number of actions allowed

    for (int i = 0; i < size; i++)
    {       
        result[rowNum][colNum] = result[rowNum][colNum] + row[i] * col[i];
        countNumOfActions++;
        // Reached the number of allowed actions
        if (countNumOfActions >= maxActions)
        {
            countNumOfActions = 0;
            maxActions = randomize();
            yield();
        }   
    }
    isFinished[rowNum][colNum] = true;
    notify();
}

打印每个单元格结果的线程:

Thread that prints the result of each cell:

public void run()
{
    int j = 0; // Columns counter
    int i = 0; // Rows counter
    System.out.println("The result matrix of the multiplication is:");

    while (i < creator.getmThreads().length)
    {
        synchronized (this)
        {
            try 
            {
                this.wait();
            } 
            catch (InterruptedException e1) 
            {
            }
        }
        if (creator.getmThreads()[i][j].getIsFinished()[i][j] == true)
        {
            if (j < creator.getmThreads()[i].length)
            {
                System.out.print(creator.getResult()[i][j] + " ");
                j++;
            }
            else
            {
                System.out.println();
                j = 0;
                i++;
                System.out.print(creator.getResult()[i][j] + " ");
            }
        }
    }

现在它向我抛出这些异常:

Now it throws me these exceptions:

Exception in thread "Thread-9" java.lang.IllegalMonitorStateException
    at java.lang.Object.notify(Native Method)
    at multiplyThread.run(multiplyThread.java:49)
Exception in thread "Thread-6" Exception in thread "Thread-4" java.lang.IllegalMonitorStateException
    at java.lang.Object.notify(Native Method)
    at multiplyThread.run(multiplyThread.java:49)
java.lang.IllegalMonitorStateException
    at java.lang.Object.notify(Native Method)
    at multiplyThread.run(multiplyThread.java:49)
Exception in thread "Thread-5" java.lang.IllegalMonitorStateException
    at java.lang.Object.notify(Native Method)
    at multiplyThread.run(multiplyThread.java:49)
Exception in thread "Thread-8" java.lang.IllegalMonitorStateException
    at java.lang.Object.notify(Native Method)
    at multiplyThread.run(multiplyThread.java:49)
Exception in thread "Thread-7" java.lang.IllegalMonitorStateException
    at java.lang.Object.notify(Native Method)
    at multiplyThread.run(multiplyThread.java:49)
Exception in thread "Thread-11" java.lang.IllegalMonitorStateException
    at java.lang.Object.notify(Native Method)
    at multiplyThread.run(multiplyThread.java:49)
Exception in thread "Thread-10" java.lang.IllegalMonitorStateException
    at java.lang.Object.notify(Native Method)
    at multiplyThread.run(multiplyThread.java:49)
Exception in thread "Thread-12" java.lang.IllegalMonitorStateException
    at java.lang.Object.notify(Native Method)
    at multiplyThread.run(multiplyThread.java:49)

multiplyThread 中的第 49 行是notify()"..我想我需要以不同的方式使用同步，但我不确定如何使用.

line 49 in multiplyThread is the "notify()"..I think I need to use the synchronized differently but I am not sure how.

如果有人可以帮助此代码工作，我将不胜感激.

If anyone can help this code to work I will really appreciate it.

推荐答案

为了能够调用notify() 你需要在同一个对象上同步.

To be able to call notify() you need to synchronize on the same object.

synchronized (someObject) {
    someObject.wait();
}

/* different thread / object */
synchronized (someObject) {
    someObject.notify();
}

这篇关于如何在没有 IllegalMonitorStateException 的情况下在 Java 中使用等待和通知?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！