ThreadGroup.activeCount()方法在Java中不起作用

我正在学习多线程的概念,在这里我试图找到数组中活动线程的数量,但是 ThreadGroup.activeCount() 的方法>只会返回零值。

代码如下:

线程对象类:-

class th1 extends Thread
{
    public th1(String threadName,ThreadGroup tg1)
    {
        super(tg1,threadName);
    }

    @Override
    public void run() 
    {
        try {
            Thread.sleep(5000);
        } 
        catch (InterruptedException e) 
        {
            e.printStackTrace();
        }

        System.out.println(Thread.currentThread().getName() + " is running");
    }
}

主班:-

public class enumerate_demo 
{
    public static void main(String[] args) 
    {
        ThreadGroup tg1 = new ThreadGroup("group 1");

        Thread t1 = new Thread(new th1("t-1",tg1));
        t1.start();

        Thread t2 = new Thread(new th1("t-2",tg1));
        t2.start();

        Thread t3 = new Thread(new th1("t-3",tg1));
        t3.start();

        System.out.println("Number of active count :- " + tg1.activeCount());

        Thread[] group = new Thread[tg1.activeCount()];

        int count = tg1.enumerate(group);

        for (int i = 0; i < count; i++)
        {
            System.out.println("Thread " + group[i].getName());
        }
    }
}
powerbww 回答:ThreadGroup.activeCount()方法在Java中不起作用

问题在于,在创建实例th1类时,您将它们用作Runnable,而与Thread相对。而且那些包装线程不与任何ThreadGroup关联。声明变量,如下所示。

        Thread t1 = new th1("t-1",tg1);
        t1.start(); 
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