Where can I find a set of Java test programs with injected errors?

Question

I need some fairly simple Java test programs with injected errors in order to test something I'm working on on them.

Edit: By "injected errors" I mean broken algorithms, errors that may cause the program to crash, and so on...

Edit2: I'm making something that tries to give some hints to the programmer about the cause of the error, so the programs should be fairly simple and contain known errors in them.

Answer 1

Maybe something like WebGoat? It is a java web app with security errors.

I'm not sure if those are the "injected errors" you are looking for.

Answer 2

I've broken a few of J2EE and Swing sample programs for a study that I did, I can share the sources if you need.