java - 在 Java 中使用 Thread.yield()

Question

我有以下类(class):

package net.adjava.multithreading;

public class MyResource {

    private int a;



    public int getA() {
        return a;
    }

    public void setA(int a) {
        this.a = a;
    }

}

---

package net.adjava.multithreading;

public class Thread1 extends Thread {
    MyResource m;

    public Thread1(MyResource m) {
        super();
        this.m = m;
    }

    @Override
    public void run() {
        System.out.println("Current Thread name1 :"
                + Thread.currentThread().getName());

        for (int i = 0; i < 10000; i++) {
            m.setA(i);
            System.out.println("Set method sets the value of a as: " + i);
            System.out.println("Current Thread name1 :"
                    + Thread.currentThread().getName());

            Thread.yield();

        }
    }
}

---

package net.adjava.multithreading;

public class Thread2 extends Thread {

    MyResource m;
    public Thread2(MyResource m) {
        super();
        this.m = m;
    }
    @Override
    public void run() {
        System.out.println("Current Thread name2 :" + Thread.currentThread().getName());

        for (int i = 0; i < 100; i++) {

            System.out.println(" value of a as per getter method is :"
                    + m.getA());
            System.out.println("Current Thread name2 :" + Thread.currentThread().getName());


        }
        System.out.println("waiting for thread to end");

    }

}

---

package net.adjava.multithreading;

public class ThreadExecutionPoint {

    public static void main(String args[])
    {
        System.out.println("Current Thread name main :" + Thread.currentThread().getName());

        MyResource m = new MyResource();
        Thread1 th1 = new Thread1(m);
        Thread2 th2 = new Thread2(m);
        th1.start();
        th2.start();

    }
}

我试图通过上述类来理解 yield() 的用途。在尝试这个例子之前，我对 yield() 的全部了解是它会暂停调用它的线程。所以为了测试它，我使用了 Thread1 类中的 yield 方法。所以基本上根据我的理解，thread1 应该执行 for 循环一次，然后应该暂停并等待其他线程完成。但输出显示不同的结果。输出显示首先执行 thread1，然后执行 thread2。有人可以纠正我所缺少的吗？或者我对 yield() 的理解有问题。

Answer 1

文档指出这与yield 方法有关:

Causes the currently executing thread object to temporarily pause and allow other threads to execute.

即使认为可能会发生这种情况，也无法保证将被选择进行处理的线程不是同一线程。

由于几乎所有协调线程，请不要依赖它，因为无法保证您期望的功能。