Java Thread.activeCount() Method

// Java program to demonstrate the 
// Thread.activeCount() method
public class Geeks {
    public static void main(String[] args) {
      
        // Create and start threads
        Thread t1 = new Thread(() -> {
            try {
                Thread.sleep(100); 
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });
        t1.start();

        Thread t2 = new Thread(() -> {
            try {
                Thread.sleep(150); 
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });
        t2.start();

        // Get the number of active threads
        int activeThreads = Thread.activeCount();

        // Print the number of active threads
        System.out.println("Number of active threads: " 
                           + activeThreads);
    }
}

// Java Program to check the number of 
// active threads in a thread pool environment
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

class Geeks extends Thread {
    private String v;

    public Geeks(String v) {
        this.v = v;
    }

    public void run() {
        try {
            System.out.println(v + " is starting.");
            Thread.sleep(200); 
            System.out.println(v + " has finished.");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
      
        // Create a thread pool with 2 threads
        ExecutorService executor 
          = Executors.newFixedThreadPool(2); 

        // Print the initial thread count 
        System.out.println("Initial: " 
                           + Thread.activeCount()); 

        // Submit tasks to the thread pool
        executor.submit(new Geeks("Task 1"));
        executor.submit(new Geeks("Task 2"));

        // Shut down the executor service immediately
        executor.shutdown(); 

        // Print the final thread count 
        // after tasks complete
        System.out.println("Final: " 
                           + Thread.activeCount()); 
    }
}