Comment 12 for bug 1000272

wuuuuiiieeeeh, this finally solved the problem for me too!

Exactly those two packages libswt-gtk-3.5-jni and libswt-gtk-3.5-java were on my system with this "versionbump" suffix and /etc/alternatives/swt.jar pointed to /usr/lib/java/swt-gtk-3.5.1.jar

After removing them, complete removal of all eclipse packages and the ~/.eclipse folder Synaptic first refused to reinstall eclipse because of missing dependencies - aaaha!
Needed to refresh/reload the package informations then everything worked!