Historically, Java has been the only officially-supported language for Android development. That changed last year, when Kotlin support was announced at Google I/O. Even though Kotlin still uses the Java Virtual Machine and can interact with Java code, there are some key changes that make some tasks significantly easier.

Google has continued to improve Kotlin support since then, most recently with the Android KTX library for Android Studio. As part of Android P, apps written in Kotlin will be faster, particularly when it comes to loops. Google is also working with JetBrains (the developers of Kotlin) to optimize compiled code, but that's not necessarily dependent on Android P.