If you need to install Oracle Java on Ubuntu 13.04 here is a way to do it. This guide will explain how to install Java (version 8, 7 or 6). You can install Java by adding the Webup8 Team Oracle Java (JDK) 6 / 7 / 8 Installer PPA.
Before you can install Java you need to remove OpenJDK (if installed), to remove it open a terminal window (press Ctrl+Alt+T) and copy+paste the following line>:
sudo apt-get purge openjdk*
To add the PPA copy+paste the following line:
sudo add-apt-repository ppa:webupd8team/java
Depending on the version you want install copy+paste one of the following lines:
sudo apt-get update && sudo apt-get install oracle-java8-installer
sudo apt-get update && sudo apt-get install oracle-java7-installer
sudo apt-get update && sudo apt-get install oracle-java6-installer
When installed close the terminal window.