Apache projects... Perhaps someone at Jakarta already has an idea for a common Preferences library? (AFAICT not)
It's common enough that everybody invents its own solution, as expected. Avalon provides for XML configuration files, there are classes mapping XML structures conveniently to objects, which can be passed to Avalon components. That's one of the more amenable features of Avalon. There's also jakarta commons configuration, which uses property files (IIRC, may well be wrong). Other approaches include using commons digester or betwixt for reading XML, using a handcrafted XML reader as 0.20.5 does, or using JNDI like J2EE.
No shortage of ideas at all :-)