Java ThreadGroup activeCount()用法及代碼示例

ThreadGroup類activeCount()方法

• activeCount() 方法可在java.lang包。
• activeCount() 方法是一個靜態方法，它也可以通過類名訪問。
• activeCount() 方法用於返回當前線程線程組中的活動線程數。
• activeCount() 方法當沒有活動線程處於活動狀態時不會引發任何異常。

用法:

    static int activeCount();

參數：

• 此方法不接受任何參數。

返回值：

這個方法的返回類型是int，它返回線程組當前線程中的活動線程數。

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());
        }
    }
}

輸出

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