This week's book giveaway is in the Performance forum. We're giving away four copies of The Java Performance Companion and have Charlie Hunt, Monica Beckwith, Poonam Parhar, & Bengt Rutisson on-line! See this thread for details.
Good question. I'm a beginner as well but here's what I know.
floats were left out on j2me. Including them will cause the code to not compile. If you needed it for money values and it is very simple, you can use two integers, one for dollars and one for cents (or whatever currency is desired).