Today one of the java.lang.* secrets disclosed itself to me (through a willing hand from the maven user list)

Runtime version inspection of packages (provided you have decent manifest.mf files, and do use maven if you don't)

1. http://java.sun.com/products/jdk/1.2/docs/guide/versioning/spec/VersioningSpecification.html#PackageVersioning

2. http://java.sun.com/j2se/1.4.1/docs/api/java/lang/Package.html

The more you investigate, the more you learn that there is soooo much more to learn... specially about the stuff you thought you already knew all there is to know about...