Java Java.lang.ThreadGroup.activeCount()用法及代碼示例

描述

這個java.lang.ThreadGroup.activeCount() 方法返回此線程組中活動線程數的估計值。

聲明

以下是聲明java.lang.ThreadGroup.activeCount()方法

public int activeCount()

參數

NA

返回值

此方法返回此線程組中以及將此線程組作為祖先的任何其他線程組中活動線程數的估計值。

異常

NA

示例

下麵的例子展示了 java.lang.ThreadGroup.activeCount() 方法的用法。

package com.tutorialspoint;

import java.lang.*;

public class ThreadGroupDemo implements Runnable {
   public static void main(String[] args) {
      ThreadGroupDemo tg = new ThreadGroupDemo();
      tg.func();
   }

   public void func() {
      try {     
         // create a parent ThreadGroup
         ThreadGroup pGroup = new ThreadGroup("Parent ThreadGroup");
    
         // create a child ThreadGroup for parent ThreadGroup
         ThreadGroup cGroup = new ThreadGroup(pGroup, "Child ThreadGroup");

         // create a thread
         Thread t1 = new Thread(pGroup, this);
         System.out.println("Starting " + t1.getName() + "...");
         t1.start();
            
         // create another thread
         Thread t2 = new Thread(cGroup, this);
         System.out.println("Starting " + t2.getName() + "...");
         t2.start();
            
         // display the number of active threads 
         System.out.println("Active threads in \"" + pGroup.getName() 
            + "\" = " + pGroup.activeCount());

         // block until the other threads finish
         t1.join();
         t2.join();
      } catch (InterruptedException ex) {
         System.out.println(ex.toString());
      }
   }

   // implements run()
   public void run() {

      for(int i = 0;i<1000;i++) {
         i++;
      }
      System.out.println(Thread.currentThread().getName() + " finished executing.");
   }
}

讓我們編譯並運行上麵的程序，這將產生以下結果——

Starting Thread-0...
Starting Thread-1...
Active threads in "Parent ThreadGroup" = 2
Thread-0 finished executing.
Thread-1 finished executing.