thread group enumeration

gistfile1.java

package testthread;

import java.util.concurrent.CountDownLatch;

public class Main {

    
    public static void main(String[] args) throws InterruptedException {
        
        final int size = 3;
        final CountDownLatch latch = new CountDownLatch(1);
        
        Thread t = new Thread(new Runnable() {
            
            @Override
            public void run() {
                try {
                    latch.countDown();
                    Thread.sleep(1000*1000);
                } catch (InterruptedException e) {

                }
            }
            
            
        });
        t.setDaemon(true);
        t.start();
        latch.await();
        ThreadGroup group = Thread.currentThread().getThreadGroup();
        System.out.println(group.activeCount());
        Thread[] threads = new Thread[size];
        int enumerate = group.enumerate(threads);
        System.out.println(enumerate);
        System.out.println(threads.length);
      }
    
     //size=0
     //2
     //0
     //0
    
    //size=1
    //2
    //1
    //1
    
  //size=2
    //2
    //2
    //2
    
  //size=3
    //2
    //2
    //3
}