2017-05-18 Kotlin on Android. Now official 2017-05-18 Kotlin and Android
Kotlin is expressive, concise, extensible, powerful, and a joy to read and write. Best of all, it's interoperable with our existing Android languages and runtime. 它强大而简洁，兼容现有的开发语言和 runtime。
Kotlin works side by side with Java and C++ on Android. So you can keep your existing code, continue to use the various Android libraries, and incrementally add Kotlin code to your project. Kotlin is a drop-in replacement you can use bi-directionally. 可以在项目中同时使用 Kotlin 和 Java 进行开发，因为可以互相调用。
IDE support: Starting with Android Studio 3.0, tooling support for Kotlin is bundled directly into Android Studio. Kotlin 的工具包会内置到 AS3.0
- developer.android.com Get Started with Kotlin on Android & FAQ
- kotlinlang.org Tutorials & FAQ