The hardest part about programming for me is figuring out how to import the necessary library files for what I want to do. I'm trying to extend the interfaces described here: http://java.sun.com/docs/books/tutorial/collections/interfaces/index.html But xCode "cannot find symbol"! Is this not already built-in stuff? If not, how do I import it so that I can use it? I appreciate any help you can provide! Thanks!