Install JDK from repository (oracle-java7-installer from this ppa is JDK)
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java7-installer
Set this version to be used by default
sudo update-java-alternatives -s java-7-oracle
Set up environment variables
sudo apt-get install oracle-java7-set-default