It’s good to use it to track your resources.

int activeCount = Thread.activeCount();
System.out.println("total active = " + activeCount);
Thread[] threads = new Thread[activeCount];
Thread.enumerate(threads);

System.out.println("before");
for (int j=0; j<threads.length; j++) {
 System.out.println(threads[j].toString());
}

//run your classes
Benny benny = new Benny();

activeCount = Thread.activeCount();
System.out.println("total active = " + activeCount);

threads = new Thread[activeCount];
System.out.println("after");
Thread.enumerate(threads);
for (int i=0; i<threads.length; i++) {
 System.out.println(threads[i].toString());
}