Program/Source Code:

The source code to destroy a thread group is given below. The given program is compiled and executed successfully.

// Java program to destroy a thread group

class MyThread extends Thread {
  MyThread(String threadname, ThreadGroup tg) {
    super(tg, threadname);
    start();
  }
  public void run() {
    try {
      Thread.sleep(100);
      System.out.println(Thread.currentThread().getName() + " is finshed");
    } catch (Exception e) {
      System.out.println(e);
    }
  }
}

public class Main {
  public static void main(String[] args) {
    try {
      ThreadGroup group = new ThreadGroup("Parent thread");

      MyThread t1 = new MyThread("Child Thread1", group);
      System.out.println(t1.getName() + " is started");

      MyThread t2 = new MyThread("Child Thread2", group);
      System.out.println(t2.getName() + " is started");

      t1.join();
      t2.join();

      group.destroy();
      System.out.println(group.getName() + " destroyed");

    } catch (Exception e) {
      System.out.println(e);
    }
  }
}

Output:

Total active threads: 3
Child Thread2 is running
Child Thread1 is running
Child Thread3 is running

Explanation:

In the above program, we created two classes MyThread and Main. We created MyThread class by extending the Thread class.

The Main class contains a main() method. The main() method is the entry point for the program. Here, we created an object of ThreadGroup class and added the child thread into the thread group. After that, we destroyed the thread group using destroy() method.