为什么join（）现在在这里工作？

Question

这是我的线程：

public class MyThread implements Runnable {
//Limits
int lowerLimit;
int upperLimit;
MyInteger result;

//Constructor
public MyThread(int lowerLimit, int upperLimit, MyInteger result){
    this.lowerLimit = lowerLimit;
    this.upperLimit = upperLimit;
    this.result = result;
}

@Override
public void run() {

    //Sums up the numbers in the given interval
    for(int i= lowerLimit; i <= upperLimit;i++){
        result.add(i);
    }
}

}

它得到一个上限和下限以及一个在所有线程上共享的结果。

这是我的测试类：

public class Sum {

public static long sumThreads(int numberThreads, int n) {

    Thread[] threads = new Thread[numberThreads];
    MyInteger result = new MyInteger(0);

    // Creates new threads and starts them
    for (int i = 0; i < numberThreads; i++) {
        threads[i] = new Thread(new MyThread(i * n / numberThreads + 1,
                (i + 1) * n / numberThreads, result));
        threads[i].start();
    }

    // Waits for all thread to continue with the return
    for (int i = 0; i < threads.length; i++) {
        try {
            threads[i].join();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    return result.getValue();
}

public static void main(String[] args) {
    System.out.println(sumThreads(10, 1000));
}

}

public MyInteger(int value) {
    this.value = value;
}

public long getValue() {
    return value;
}

public void setValue(int value) {
    this.value = value;
}

public void add(int summand){
    value += summand;
}

public void sub(int decr){
    value -= decr;
}

public void increase(){
    value++;
}

public void decrease(){
    value--;
}
}

Answer 1

您的联接代码看起来正确。我怀疑您的代码正在经历竞争危险:

关于争用条件的Wiki页面

当您有多个线程同时运行（所有线程都在修改共享资源）时，您需要确保它们在执行修改时具有独占访问权。

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