PATTERNS: knit one, pearl one
In books like the racy The Struts Framework, you will often come across stuff like:
"The ActionServlet represents the Controller in the MVC design pattern. Additionally, the ActionServlet implements both the Front Controller and the Singleton pattern"
If you havn't a clue what this man is talking about, then you need to get into design patterns. Gamma et al describe them as:
"A design pattern systematically names, motivates, and explains a general design that addresses a recurring design problem in object-oriented systems. It describes the problem, the solution, when to apply the solution, and its consequences. It also gives implementation hints and examples. The solution is a general arrangement of objects and classes that solve the problem. The solution is customized and implemented to solve the problem in a particular context."
For a brilliant and very readable introduction to patterns i'd reccomend, Java Design Patterns - A Tutorial. Equally brilliant from a J2EE perspective are: Core J2EE patterns and Patterns of Enterprise Application Architecture.
If your feeling keen, you could attempt the seminal work: Design Patterns by the Gang of Four. This is a bit more hard work (all the examples are in C++) but rewarding in a slightly pervy computer-science-tanktop kind of way.
Finally, if you arrived here by mistake and are thinking "who this pompous git showing off about his dull computer books" perhaps you'd be better of with Brenda's crayon scribble pullover.