Mohamed, I'm not too familiar with RAD, but NetBeans is a great
Java IDE (though it supports a number of other development paradigms (Ruby, C/C++, etc.).
I could go on forever on the features and why I feel it is better than another IDE, but that would only ignite an "my IDE is better than your IDE" war which we've all seen too many times!
Start with browsing the NetBeans features :
http://www.netbeans.org/features/index.html ... and then try downloading NetBeans 6.1. Seeing/trying is believing.