Have you tried to put Try and Catch blocks around your code to see what the exception is?

That what you want to college for. Try to design the algorithm your self. Show that you have tried something your self than you might get some help.

People are not help you because what you asked is a easy question. Any one with a degree in CS should be able to done this.

Hey, If you have to real degrees in computer science is should be easy for you. So you should do your homework your self or you will never make it as a software engineer.