Create integration example in Java

[pedropintosilva]

Potential mentors: @mcecchetti

Detailed description and rationale

Currently we have integration examples using different programming languages as you can see in this repository. And they are then linked to SDK docs. Nevertheless there are still many languages to go such as Java ;)

Code pointers

The goal here is to do something quite minimal in complexity so it can be a great start for anyone trying to do a new integration.

Thanks !