I have posted the hundreds of megabytes of source code in the Java class libraries and reference VM implementation. Legally speaking you must be a Sun Community Source licensee to view these files. The link can be found on my home page under Code Resources. It is:
Java Development Kit Source Code
If you have not perused the source code before you will notice it has lots of interesting stuff in it like test routines, the full source to the reference compiler, make files so you can actually build all the binaries, the browser plug-in source, the javac compiler tool source (with Java code parser) and a lot of other neat stuff.