java.lang.ThreadGroup.activeCount() 方法返回活動線程在該線程組的數目的估計值。

聲明

以下是java.lang.ThreadGroup.activeCount()方法的聲明

public int activeCount()

參數

• NA

返回值

此方法返回此線程組和具有該線程組作為祖先的任何其它線程組活動線程的數目的估計值。

異常

• NA

例子

下麵的例子顯示java.lang.ThreadGroup.activeCount()方法的使用。

package com.yiibai;

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.");
   }
} 

讓我們來編譯和運行上麵的程序，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