In Java terms, Kotlin classes are final by default. Default public members and default final classes could be interpreted as subtle encouragement to prefer composition over inheritance.

A Kotlin file can contain multiple/mix of class declarations, functions and other constructs like enum classes. This opens up a lot of possibilities not available in Java.

The appeal of Kotlin among Android developers is straightforward: It's a statically typed language -- similar to Scala, Gosu, Ceylon and Fantom -- which compiles to both JVM byte code and JavaScript.

Apache Spark has a Java API, which allows developers to use Kotlin to work with it, but JetBrains is working to add full support for Kotlin class and support for Kotlin in Spark’s shell.

JetBrains is planning “another step forward for the Kotlin ecosystem,” in the next release of the programming language. While Kotlin 1.4 is not expected to arrive until the spring of next year ...