Java Thread activeCount()方法

Thread类的activeCount()方法用于返回当前线程的线程组中活动线程的数量。返回的值只是一个估计值，因为当此方法遍历内部数据结构时，线程数可能会动态更改。

语法

public static int activeCount()

返回

它返回当前线程的线程组中活动线程的数量。

示例

public class JavaActiveCountExp extends Thread   
{  
    JavaActiveCountExp(String threadname, ThreadGroup tg)  
    {  
        super(tg, threadname);  
        start();  
    }  
    public void run()  
    {  
       System.out.println("running thread name is: "+Thread.currentThread().getName());    
    }  
    public static void main(String arg[])  
    {  
        // creating the thread group  
        ThreadGroup g1 = new ThreadGroup("parent thread group");  

        // creating a thread   
        JavaActiveCountExp t1 = new JavaActiveCountExp("Thread-1", g1);  
        // creating another thread   
        JavaActiveCountExp t2 = new JavaActiveCountExp("Thread-2", g1);  

        // checking the number of active thread  
        System.out.println("number of active thread: "+ g1.activeCount());  
    }  
}

执行上面示例代码，得到以下结果：

number of active thread: 2
running thread name is: Thread-1
running thread name is: Thread-2