Few years ago I passed SCJP (Sun Certified Java Programmer) certification and, during the preparation for the test, compiled a short, 18 pages, document containing some key facts required for passing the test successfully. I "accidently" found it in my archives and decided to share it, here is the link.
The document is a collection of various facts, gathered from various books/articles as well as code examples written by me while experimenting. It doesn't always clarify each topic with great details, but this wasn't the purpose of the document. So, if you struggle with a topic and want to know more, I always recommend to consult JLS (Java Language Specification).
You are more than welcome to use it and I will be happy to know if it helped you to pass the test (or at least you find it useful) ;)