线程问题－主程序线程为什么不执行

[xingxingliang]

代码和输出结果如下， 问题是
Child #1 joined.
Child #2 joined.
Child #3 joined.
这三个主程序的语句为什么在最后执行？ 当其它线程sleep的时候，主程序还不能执行吗？
为什么？ 谢谢！

using System;
using System.Threading;

class MyThread
{
public int count;
public Thread thrd;

public MyThread(string name)
{
count = 0;
thrd = new Thread(run);
thrd.Name = name;
thrd.Start();
}

void run()
{
Console.WriteLine(thrd.Name + " starting.");

do
{
Thread.Sleep(1000);
Console.WriteLine("In " + thrd.Name +
", count is " + count);
count++;
} while (count < 5);

Console.WriteLine(thrd.Name + " terminating.");
}
}

class MainClass
{
public static void Main()
{
Console.WriteLine("Main thread starting.");

MyThread mt1 = new MyThread("Child #1");
MyThread mt2 = new MyThread("Child #2");
MyThread mt3 = new MyThread("Child #3");

mt1.thrd.Join();
Console.WriteLine("Child #1 joined.");

mt2.thrd.Join();
Console.WriteLine("Child #2 joined.");

mt3.thrd.Join();
Console.WriteLine("Child #3 joined.");

Console.WriteLine("Main thread ending.");

Console.ReadLine();
}
}



这是输出结果：
Main thread starting.
Child #1 starting.
Child #2 starting.
Child #3 starting.
In Child #2, count is 0
In Child #1, count is 0
In Child #3, count is 0
In Child #2, count is 1
In Child #1, count is 1
In Child #3, count is 1
In Child #2, count is 2
In Child #1, count is 2
In Child #3, count is 2
In Child #2, count is 3
In Child #1, count is 3
In Child #3, count is 3
In Child #2, count is 4
Child #2 terminating.
In Child #1, count is 4
Child #1 terminating.
In Child #3, count is 4
Child #3 terminating.
Child #1 joined.
Child #2 joined.
Child #3 joined.
Main thread ending.

[luobocheng]

join 阻塞住主线程的执行了，直到该线程结束，你如果在join函数里加参数
join（0）,那么就会按你设想的先执行完下面的
Child #1 joined.
Child #2 joined.
Child #3 joined.
再执行
In Child #2, count is 0
In Child #1, count is 0
In Child #3, count is 0
In Child #2, count is 1
In Child #1, count is 1
In Child #3, count is 1
In Child #2, count is 2
In Child #1, count is 2
In Child #3, count is 2
In Child #2, count is 3
In Child #1, count is 3
In Child #3, count is 3
In Child #2, count is 4
Child #2 terminating.
In Child #1, count is 4
Child #1 terminating.
In Child #3, count is 4
Child #3 terminating.

[ouc_ajax]

Thread类的Join()方法能够将两个交替执行的线程合并为顺序执行的线程。比如在线程B中调用了线程A的Join()方法，线程A将插入线程B之前，直到线程A执行完毕后，才会继续执行线程B。

当子线程sleep的时候父类线程是可以执行的！但是上边你把mt1.thrd.Join(); 以为着子线程先结束后主线程再执行，因此主线程肯定等待mt1执行完成。

[michaelnami]

关系到线程就不是顺序执行了 有一个线程调度机制

[Thr21ough]

up~

[xingxingliang]

哦， 他们这个join是对于主线程而言的， 所以主线程要等待他们结束。 犯了一个错误， 我以为只是对于当前线程的join, 实际这个语句的当前线程就是主线程, thanks!!!