Well you should definitely use the new collections  (i.e. HashMap,
ArrayList, etc.) in favor of the old ones (i.e. Hashtable, Vector). The
type of collection  you use depends on whether you want a list of things
(then you'd use ArrayList, LinkedList or something similar) or a map
which maps keys to values (in which case you'd probably use HashMap).
HashMap stores keys in any order but there are also variations which
provide sorting by natural order. Additionally there are utility
methods in Collections which help with this as well.

Try java.sun.com/docs/books/tutorial/collections/ for more
information.