Java中的ThreadGroup

Question

我目前正在学习Java中的线程基础知识，并且正在尝试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，但我和教程网站一样写了它。下面是我的代码，我得到不同的输出。

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(); 
    } 

} 

我越来越 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] 

---

输出应该是这样的：

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] 

我不能够理解为什么会这样呢？设置优先级可以帮助它吗？

Answer 1

即使拥有一定的优先级，您也无法预测线程的执行顺序。您无法控制调度。这是你的操作系统决定的。

一本好书，关于并发在Java中：Java concurrency in practice