Screaming Penguin - Source Does Matter

Good intro to using the Generics system in JDK1.5+ at JavaPro today.
Short summation: Great feature, FUGLY syntax.
The whole thing really boils down to letting the compiler create Class specific versions of more generic classes without your having to code a wrapper that type checks. IE:

List<? extends Number> ref = new LinkedList<Integer>();

gives you a LinkedList that will only accept Integer class types.