I haven't taken a detailed look at J2SE 1.5 and was sniffing around for some sources. If you haven't yet, check out the article J2SE 1.5 in a Nutshell by Calvin Austin. It is a great overview of J2SE 1.5, complete with code snippets in the appropriate places. Calvin is the is the Specification Lead for the Java 2 Standard Edition 1.5 and also an editor for Java Developer's Journal.
A good overview diagram for J2SE 1.5 can be found at Sun's site.