In studying for the SCJP exam I stumbled upon this neat little link explaining a fundamental Java topic. The overriding of equals and hashcode. More speficially the title of the article is:
How to Write an Equality Method in Java (http://www.artima.com/lejava/articles/equality.html)
This is basic stuff but since the SCJP requires you to be a human Java compiler, rather than relying on a IDE like Eclipse, it's important to go over it.