A powerful suite of tools for Java developers by Oracle. It has enterprise features like EJB support which I haven't used much. The Java IDE looks very similar to JBuilder, especially the layout managers editing in the GUI designer. The performance is a little bit slow but it is quite stable. Anyway JBuilder is a better choice to me if only Java application development is concerned.
The latest JDeveloper version is 10g, can be obtained free here
if you are a registered OTN member (free).