There is a site with lots of helpful answers for java programmers:
I went ahead and tried http://enthuware.com/ product and it is really good for 10$.
Initially I wasn't going to buy any software figuring I know java really well but the test questions are really specific for things that are often times not commonly used or common knowledge. Suffice to say, I am extremely happy I bought a practice test because I scored 50% on the first practice test and it is a long way up to 75%.
It would have been incredibly embarrassing for my company to pay for the certification 300$ and find out the hard way I that I wasn't prepared.
I wouldn't buy just any practice tests because they are not equal and some are complete scams. You need to do your research and find ones that other people have used.
P.S. : thanks to using that software i passed with a 93%, otherwise i definitely would have failed.