How to install Oracle Java 1.7 and 1.8 on Ubuntu 14.04?

Install Java version 1.7

Install Java version 1.8

via PPA:

sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java7-installer
sudo apt-get install oracle-java8-installer

Set Java 1.7 as default version:
sudo update-java-alternatives -s java-7-oracle

To set environmental variables to Java 7, install:
sudo apt-get install oracle-java7-set-default