It seems as though I can save some user preferences using java.util.prefs.Preferences. The preferences are tied to the specific classes -- I get a Preferences instance by passing a class Object to some static method, e.g. Preferences.userNodeForPackage.
However, what happens if I delete my class and never use it anymore? What happens to the stored data? Is it just going to leak memory in my harddrive? Is there some nice way I can browse through my current Preferences data?