To get started with Kotlin, download the Android Studio 3.0 preview, open one of your existing Java files, and then choose “Convert Java File to Kotlin File” in the Code menu.

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.

That’s important because if you want to target Android O, create an Instant App, start developing with Kotlin, or use the latest Android app performance tools, you’ll need Android Studio 3.0.

Kotlin offers big advantages over Java for JVM and Android development, and plays nicely with Java in the same projects.

This is what libraries in Android Studio are for. They simply extend the capabilities of Java/Kotlin/the Android SDK by letting you use classes and methods built by other users.