The GitHub API for Java Library is an object oriented library, with classes that correspond to GitHub's domain model. This library is authored by Kohsuke Kawaguchi and other contributors and more details can be found on their documentation site.
The Nexmo SMS API is a service that allows you to send and receive SMS messages anywhere in the world. Nexmo provides REST APIs, but it's easier to use their official Java SDK. This tutorial covers how to send and receive SMS messages with the SDK so that you can use them in your applications.