Java ThreadGroup activeCount()用法及代码示例

ThreadGroup类activeCount()方法

• activeCount() 方法可在java.lang包。
• activeCount() 方法是一个静态方法，它也可以通过类名访问。
• activeCount() 方法用于返回当前线程线程组中的活动线程数。
• activeCount() 方法当没有活动线程处于活动状态时不会引发任何异常。

用法:

    static int activeCount();

参数：

• 此方法不接受任何参数。

返回值：

这个方法的返回类型是int，它返回线程组当前线程中的活动线程数。

例：

// Java program to demonstrate the example of 
// activeCount() method of ThreadGroup Class.

import java.lang.*;

class ActiveCount extends Thread {
    // Override run() of Thread class
    public void run() {
        String name = Thread.currentThread().getName();
        System.out.println(name + " " + "finish executing");
    }
}

public class Main {
    public static void main(String[] args) {
        ActiveCount ac = new ActiveCount();
        try {

            // We are creating an object of ThreadGroup class
            ThreadGroup tg1 = new ThreadGroup("ThreadGroup 1");
            ThreadGroup tg2 = new ThreadGroup("ThreadGroup 2");

            // We are creating an object of Thread class and 
            // we are assigning the ThreadGroup of both the thread

            Thread th1 = new Thread(tg1, ac, "First Thread");
            Thread th2 = new Thread(tg2, ac, "Second Thread");

            // Calling start() method with Thread class object 
            // of Thread class 

            th1.start();
            th2.start();

            // Here we are counting active thread in ThreadGroup

            System.out.print("Active thread in:" + tg1.getName() + "-");
            System.out.println(tg1.activeCount());

            System.out.print("Active thread in:" + tg2.getName() + "-");
            System.out.println(tg2.activeCount());


            th1.join();
            th2.join();

        } catch (Exception ex) {

            System.out.println(ex.getMessage());
        }
    }
}

输出

E:\Programs>javac Main.java
E:\Programs>java Main
Second Thread finish executing
Active thread in:ThreadGroup 1-1
Active thread in:ThreadGroup 2-0
First Thread finish executing