Yes, you can use JBuilder for Mac OS X.
There are some things that you have to do though.
I don´t quite remember what it all is, but I think there is some info on the Borland page.
There should also be a how to do on
http://www.pepsan.com/macosx/java.html
I have installed JBuilder, and it seems to work quite well.
except of the annoying thing that you cannot enter these brackets with the option-key. (I mean these: {} ), so you can´t really use JBuilder.
But you can use Project Builder for doing some Java, it is quite nice, but what really is missing is the contextual help of JBuilder...