Since Gradle 3, Kotlin is the preferred language for writing build scripts and addins, rather than just Apache Groovy. If you use Kotlin instead of Java for you

Since Gradle 3, Kotlin is the preferred language for writing build scripts and addins, rather than just Apache Groovy. If you use Kotlin instead of Java for your Android coding, you can use the same language for writing your build scripts as you do for your system code.