Java ThreadGroup .uncaughtException (Thread t, Throwable e)

public void uncaughtException(Thread t,   Throwable e)

public class Main {
  public static void main(String[] args) {
    ThreadGroupDemo tg = new ThreadGroupDemo();
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  }
}

class ThreadGroupDemo implements Runnable {
  public ThreadGroupDemo() {
    MyThreadGroup pGroup = new MyThreadGroup("ParentThreadGroup");
    MyThreadGroup cGroup = new MyThreadGroup(pGroup, "ChildThreadGroup");

    Thread thr2 = new Thread(pGroup, this);
    System.out.println("Starting " + thr2.getName());

    thr2.start();

    // create third thread
    Thread thr3 = new Thread(cGroup, this);
    System.out.println("Starting " + thr3.getName());

    thr3.start();

    try {
      Thread.sleep(500);
    } catch (InterruptedException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }

    thr2.interrupt();
    thr3.interrupt();

  
  }

  public void run() {
    try {
      System.out.print(Thread.currentThread().getName());
      System.out.println(" executing...");

      while (true) {
        Thread.sleep(500);
      }
    } catch (InterruptedException e) {
      Thread currThread = Thread.currentThread();
      System.out.print(currThread.getName());
      System.out.println(" interrupted:" + e.toString());

      // rethrow the exception
      throw new RuntimeException(e.getMessage());
    }
  }
}

class MyThreadGroup extends ThreadGroup {

  MyThreadGroup(String n) {
    super(n);
  }

  MyThreadGroup(ThreadGroup parent, String n) {
    super(parent, n);
  }

  public void uncaughtException(Thread t, Throwable e) {
    System.out.println(t + " has unhandled exception:" + e);
  }
}