Here is a simple guide to install Java in Ubuntu 11.04 Natty Narwhal via PPA. In Natty the previous versions of Java will be integrated into the Canonical Partner Repository by default. To date there are no Canonical Partner Repository available, so if you want to install Java on Ubuntu 11.04 Natty you have to go for other alternatives.
The best solution is to use this PPA for more further Java updates. To install Java in Ubuntu 11.04 Natty Narwhal, open a Terminal and type :
sudo apt-get install python-software-properties
sudo add-apt-repository ppa:ferramroberto/java
sudo apt-get update
sudo apt-get install sun-java6-jre sun-java6-plugin sun-java6-fonts
During the installation press ‘OK’ in the screen that appears within the Terminal (see the below screenshot). You can do so by navigating using the ‘Tab’ key and once ‘OK’ is highlighted in red, press ‘Enter’.