There may well be a very simple answer to this but having googled for an hour, I am resorting to asking here.
I am simply trying to install eclipse Indigo(3.7.2) on Ubun
I was with the same problem. Try doing that:
sudo apt-get update && sudo apt-get upgrade
sudo apt-get remove eclipse
sudo apt-get purge eclipse
rm -r ~/.eclipse
sudo apt-get install eclipse
I didn't need to remove all the locations which showed up on whereis eclipse, like Steve Beer said.
Besides, you can also try doing
sudo apt-get install --reinstall eclipse-jdt
if the previous commands don't work out.