Eclipse installation in ubuntu 12.04 is very simple . you can install eclipse using “software center” but you may not get the latest version, better download the latest version and install manually . Here we can see how to install eclipse in ubuntu manually .

Installing eclipse in ubuntu 12.04

Step 1 » Before installing eclipse you need to install java , you can either install JRE or JDK .
krizna@leela:~$ sudo apt-get install openjdk-7-jre
[or]
If you are going to use eclipse for java development, then you can install JDK
krizna@leela:~$ sudo apt-get install openjdk-7-jdk
Step 2 » Download the latest eclipse package from here http://www.eclipse.org/downloads/?osType=linux
Step 3 » move the package to the /opt directory
krizna@leela:~$ sudo mv eclipse-SDK-4.2.2-linux-gtk.tar.gz /opt/
Step 4 » Unzip the package by typing the below command
krizna@leela:~$ cd /opt
krizna@leela /opt:~$ sudo tar -xvf eclipse-SDK-4.2.2-linux-gtk.tar.gz
Step 5 » Create a new desktop file eclipse.desktop in /usr/share/applications/ and add the below lines .

[Desktop Entry]
Name=Eclipse 
Type=Application
Exec=/opt/eclipse/eclipse
Terminal=false
Icon=/opt/eclipse/icon.xpm
Comment=Integrated Development Environment
NoDisplay=false
Categories=Development;IDE
Name[en]=eclipse.desktop

Step 6 » Now goto /usr/share/applications and find eclipse.desktop file for launching eclipse , you can drag this file to the launcher.

good luck