Android Studio will walk you through adding Kotlin dependencies into your project and convert the code to functionally equivalent Kotlin code.

What are extension functions? Kotlin’s extension functions provide you with a way of “adding” methods to a class, without having to inherit from that class or use any type of design pattern.

Google's Android Studio 3.0 dev environment has just become available in the stable channel, with built-in support for Kotlin and Java 8.