Install Oracle JRE from oracle.com, where you can find the latest JRE to be installed. Download the binaries from http://cassandra.apache.org/download/. You have the choice of installing a Ubuntu or tar package from the site. DataStax has an installation package, which is distributed at http://www.datastax.com/download.
Follow the instructions and get it installed; once installed, you will find the following files in the respective locations:
It is advisable to ...