What is the purpose of annotations in Java? I have this fuzzy idea of them as somewhere in between a comment and actual code. Do they affect the program at run time?
To see some cool stuff you can do with Annotations, check out my JavaBean annotations and annotation processor.
They're great for generating code, adding extra validations during your build, and I've also been using them for an error message framework (not yet published -- need to clear with the bosses...).