What is a IncompatibleClassChangeError exception in Java?

Question

i am working on a small application and I am trying to use Hibernate Annotations to map my entities. I wanted to test if everything is alright when i got this exception :

Answer 1

Right, erickson has identified the issue correctly.

This is likely caused by having two conflicting versions of the same type definition in your classpath. For example, library-version2.jar defines some stuff, but you've also got library-version5.jar in your classpath.

At runtime, this results in the pain and suffering erickson describes.