怎么调出并发不确定性的效果

Question

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();

        

        System.out.println("Hello from main Thread!");

        myThread.join();

    }

}

《七周七并发模型》

作者说结果可能是

结果可能一

Hello from main Thread!

Hello from new Thread!

结果可能二

Hello from new Thread!

Hello from main Thread!

为什么我的结果只有一。

Answer 1

可以用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();    }}

Answer 2

  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();    }        我把题主的yield()换成了sleep（），yield（）方法只能让同优先级的线程有执行的机会。可能是主线程比子线程优先级高