This is a regression from 3.3.

First, compile the attached source with jikes.
The problem isn't visible if you compile to .class with
"gcj -C", as gcj generates the wrong invokespecial call
for "super.dispose()".
(I'll also attach a .jar file containing the classes as
compiled with jikes).

Then compile FieldEditorPreferencePage.class with "gcj -c".
gcj generates a call to this method:

         U IPreferencePage.dispose()

However, this is an interface method, so this call is
clearly wrong.

gcj 3.3 emits a call to:

         U DialogPage.dispose()

This is still wrong, but less so -- at least it will work.
Really we should emit a call to PreferencePage.dispose().
(This is especially true for binary compatibility.)