We need Java in order to have Cassandra running since Cassandra 2.0 and later require Java 7 or later. And we need Cassandra in order to run Kong.
So lets start installing Java 8 (the newest one)
First we add a repository to our build in order to manage the Java 8 package, since that is not normally supported by Ubuntu.
sudo add-apt-repository ppa:webupd8team/java