If your hardcoded values are just simple key-value pairs, you should look at java.util.Properties. It's a lot simpler than xml, easier to use, and mind-numbingly trivial to implement.
If you are working with Java and the data you are storing or retrieving from disk is modeled as a key value pair (which it sounds like it is in your case), then I really can't imagine a better solution.
I have used properties files for simple configuration of small packages in a bigger project, and as a more global configuration for a whole project, and I have never had problems with it.
Of course this has the huge benefit of not requiring any 3rd party libraries to utilize.
