Currently, Swing has a machinery to deal with GTK library in the following file (but not restricted by):
AWT may pick those functionality to deal with GTK API in a particular way:
1) to read GTK properties to get closer to GNOME (mouse timings is one of them)
2) to invoke GTK functions supporting desktop integration with mail agent, browser, etc.
3) to simplify possible implementation of bundles splitting for Java kernel on unix.