We have concluded our lessons on Object Oriented Programming. We learnt how we can use classes to organize and reuse our code in powerful ways, and we've started to see how classes and objects are used throughout Android.

We will continue to explore the Android SDK, but there is much more to Java's OOP model that you can learn if you are interested. While we have covered the basics that we need in Android, there are other features that can help you write more concise code.

A good jump off point is Oracle's tutorial articles: https://docs.oracle.com/javase/tutorial/java/index.html

We have touched on content in Object-Oriented Programming Concepts, Classes and Objects, Interfaces and Inheritance. After the course, I'd recommend going through this series to fill in the gaps in our Java knowledge. Having used what we know in practice, we can have a much better appreciation of the more advanced topics.