java - 怎么调出并发不确定性的效果

Question

{代码...} 《七周七并发模型》 作者说结果可能是 结果可能一 {代码...} 结果可能二 {代码...} 为什么我的结果只有一。

天蓬老师 · Answer

You can use sleep:

class HelloWorld {
    public static void main(String[] args) throws InterruptedException {
        Thread myThread = new Thread() {
            public void run(){
                System.out.println("Hello from new Thread!");
            }
        };
        
        myThread.start();
        Thread.yield();
        Thread.sleep(100);
        System.out.println("Hello from main Thread!");
        myThread.join();
    }
}

伊谢尔伦 · Answer

  public static void main(String[] args) throws InterruptedException {
        Thread myThread = new Thread(){
            public void run(){
                try {
                    Thread.sleep(500);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Hello from new Thread!");
            }
        };
        
        myThread.start();
        Thread.sleep(500);
        
        System.out.println("Hello from main Thread!");
        myThread.join();
    }

I replaced the yield() in the question with sleep(). The yield() method can only give threads with the same priority a chance to execute. It may be that the main thread has a higher priority than the child thread