Originally posted by Jignesh Patel: Put all the threads in thread group. In a while(true)loop continues check for threadgroup.activeCount()==0.
The activeCount() method is documented as being approximate, so it probably isn't a good one to use here. Instead, keep track of all the threads that you've fired off, then join() them all. Note that you can join() them in any order; you don't have to join() them in the same order that they finish.
Betty Rubble? Well, I would go with Betty... but I'd be thinking of Wilma.