Design Java Swing-based user interfaces with Apple's Interface Builder

nib4j 1.0 is a simple but powerfull Java library that permits the use of
Apple's Interface Builder to design Swing-based user interfaces. It creates
Swing menus, frames and dialogs from Carbon nib files and provides a
complete separation of UI and application code. nib4j supports both absolute
and relative positioning/sizing, internationalization and more than 25 UI
controls, including real floating palette windows and Mac OS X 10.3 group
boxes. By using the included "nib4j Viewer" you can try out your UI without
writing any code and generate the necessary Java source to access the Swing
components. For non-commercial use nib4j is completely free.

More informations at:
http://www.nib4j.com