Watch this video to learn how to install Eclipse Luna or any version of Eclipse on Ubuntu 14.04 LTS or any recent versions of Ubuntu.
Download eclipse tar.gz file. Eg: eclipse-jee-luna-SR1a-linux-gtk.tar.gz
Extract the package in same place
open nautilus as root
copy eclipse from Downloads to /opt/ and rename the folder as eclipse-luna.
it will look like /opt/eclipse-luna
open gedit as root from terminal