查询线程加入

Question

我很困惑在线程中的uisng连接方法可以有人请解释我已经读过父线程将等待其子线程,直到子完成其操作

我有一个父线程,如下所示:

public class join implements Runnable {

    public void run() {

        System.out.println("Hi");

    }

    public static void main(String[] args) throws Exception {
        join j1 = new join();
        Thread parent = new Thread(j1);

        child c = new child();

        Thread child = new Thread(c);

        parent.start();
        child.start();
        parent.join();

    }
}

儿童线程:

    public class child implements Runnable {


            public void run() {
                    try {
                        Thread.currentThread().sleep(100000);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                            System.out.println("i m child");

            }


}

执行此操作后,输出为

你好

我的孩子

根据我的理解,它应该是相反的顺序

我的孩子

你好

如果我错了,请纠正我

Answer 1

我已经读过Parent Thread会等待它的子Thread

不,不是真的,

这个说法:

parent.join();

将阻塞当前线程(执行该线程的线程join)直到parent完成.

实际上它根本不会影响执行parent.

我将用一个例子来澄清:

class Test {
    public static void main(String[] args) throws InterruptedException {
        Thread t = new Thread() { public void run() {
            System.out.println("t: going to sleep");
            try { sleep(1000); } catch (InterruptedException e) { }
            System.out.println("t: woke up...");
        }};

        System.out.println("main: Starting thread...");
        t.start();

        Thread.sleep(500);
        System.out.println("main: sshhhh, t is sleeping...");

        System.out.println("main: I'll wait for him to wake up..");
        t.join();

        System.out.println("main: Good morning t!");
    }
}

输出(左边的时间):

   0 ms: main: Starting thread...
   0 ms: t: going to sleep
 500 ms: main: sshhhh, t is sleeping...
 500 ms: main: I'll wait for him to wake up..
1000 ms: t: woke up...
1000 ms: main: Good morning t!