Java ThreadGroup activeCount() method

The activeCount() method of ThreadGroup class is used to return the number of active threads in the current thread's thread group. The returned value is only an estimate because the number of threads may change dynamically while this method traverses internal data structures.

Syntax

Return

It returns the number of active threads in the current thread's thread group.

Example

class NewThread extends Thread 
{
    NewThread(String threadname, ThreadGroup tg)
    {
        super(tg, threadname);
    }
    public void run()
    {
        for (int i = 0; i < 10; i++) 
        {
            try
            {
                Thread.sleep(10);
            }
            catch (InterruptedException ex) 
            {
              System.out.println(Thread.currentThread().getName() + " interrupted");
            }
        }
        System.out.println(Thread.currentThread().getName() + " completed executing");
    }
} 
public class ThreadGroupActiveCountExp
{
    public static void main(String arg[])
    {
        // creating the thread group
        ThreadGroup tg1 = new ThreadGroup("parent thread group");

        // creating the threads
        NewThread t1 = new NewThread("Thread-1", tg1);
        NewThread t2 = new NewThread("Thread-2", tg1);
        NewThread t3 = new NewThread("Thread-3", tg1);
        
        // this will call the run() method
        t1.start();
        t2.start();
        t3.start();

        // checking the number of active thread
        System.out.println("Number of active thread: "+ tg1.activeCount());
    }
}

Test it Now

Output:

Number of active thread: 3
Thread-1 completed executing
Thread-2 completed executing
Thread-3 completed executing

Next TopicThreadGroup in Java

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