I've decided to write a small app in Groovy, but I plan to use Gtk/GNOME/Glade for the UI side of things.
So far, I've installed Glade (version 3) and libglade-java. It looks like libglade-java depends on libgnome-java, so I'm hoping Synaptic has pulled in all the needed dependencies to get up and running.
On Ubuntu, the jar files needed to start developing Gtk/GNOME apps live in /usr/share/java and need to get appended to the classpath. You also need to set LD_LIBRARY_PATH to include /usr/lib/jni as this is where the jni portion of the bindings live.
I just wrap all of this, plus the setting up of GROOVY_HOME and such like, into a bash script.
As I get on with the project, I'll post more