How to Install OpenJDK 7 in Ubuntu 15.04 14.10 14.04 13.04 12.04

1)
Update Repo

#sudo apt-get update

2)
Install OpenJDK 7
#sudo apt-get install openjdk-7-jre-headless



3)
Check which JDK packages are installed
#sudo dpkg --list | grep -i jdk

4)

Install Plugin for Firefox

#sudo apt-get install icedtea-plugin

5)

Verify Firefox Plugin

http://www.java.com/en/download/testjava.jsp