Java中的ThreadGroup

Question

目前，我正在学习Java中的线程基础知识，并试图编写一个简单的线程组程序。虽然我得到了不同类型的输出，但我写的和教程网站一样。下面是我的代码，我得到了不同的输出。

public class ThreadGroupDemo implements Runnable {

    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName());
        // get the name of the current thread.
    }

    public static void main(String[] args) {
        ThreadGroupDemo runnable = new ThreadGroupDemo();
        ThreadGroup tg1 = new ThreadGroup("Parent Group");
        // Creating thread Group.

        Thread t1 = new Thread(tg1, new ThreadGroupDemo(), "one");
        t1.start();
        t1.setPriority(Thread.MAX_PRIORITY);

        Thread t2 = new Thread(tg1, new ThreadGroupDemo(), "second");
        t2.start();
        t2.setPriority(Thread.NORM_PRIORITY);

        Thread t3 = new Thread(tg1, new ThreadGroupDemo(), "Three");
        t3.start();

        System.out.println("Thread Group name : " + tg1.getName());
        tg1.list();
    }

}

我得到输出:

Thread Group name : Parent Group
Three
java.lang.ThreadGroup[name=Parent Group,maxpri=10]
    second
one
Thread[one,10,Parent Group]
    Thread[second,5,Parent Group]
    Thread[Three,5,Parent Group]

产出应类似于：

one
two
three
Thread Group Name: Parent ThreadGroup
java.lang.ThreadGroup[name=Parent ThreadGroup,maxpri=10]
    Thread[one,5,Parent ThreadGroup]
    Thread[two,5,Parent ThreadGroup]
    Thread[three,5,Parent ThreadGroup] 

我不明白为什么会发生这种事？设定优先级能帮上忙吗？

Answer 1

即使在优先级级别上，也无法预测线程的执行顺序。你无法控制日程安排。是你的操作系统决定了。

一本关于Java并发性的好书：https://rads.stackoverflow.com/amzn/click/com/0321349601