Installing Java 7 on Ubuntu

Open your terminal (Ctrl + Alt + T) , and run the following commands

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

This will keep your java 7 installation up to date.

To automatically set up the Java 7 environment variables JAVA_HOME and PATH:

sudo apt-get install oracle-java7-set-default