I don't personally program in Java, but since I use Cassandra, Java is a requirement on my system.

The OpenJdk works, but it is presented as having problems when running Cassandra. Having run in a problem (see http://stackoverflow.com/questions/11182637/data-in-cassandra-not... on Stack Overflow,) I thought I would finally give a chance to Oracle and install their version to see whether that was the culprit.

I was really thinking that the OpenJdk was working fine because I have two other systems working just fine, but those two systems have Ubuntu 12.10 opposed to version 12.04 in my case.

Anyway, it was very easy to install Java and I did not have to make any changes to the existing installation (And thus the different things running Java could continue as is.)

The commands look like this:

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

That's it! It will automatically change the alternatives to that new version of Java. Once installed you can test with java -version to see that it tells you java version "1.7.0_11" (or whatever version you're installing.)

Source: http://www.webupd8.org/2012/01/install-oracle-java-jdk-7-in-ubuntu-via.html

Source: http://www.webupd8.org/2012/09/install-oracle-java-8-in-ubuntu-via-ppa.html