Retrolambda, yet another kludge, instead of invokedynamic calls.
Kotlin exists because JetBrains wants your money, that is all.
> The next thing is also fairly straightforward: we expect Kotlin to drive the sales of IntelliJ IDEA. We’re working on a new language, but we do not plan to replace the entire ecosystem of libraries that have been built for the JVM. So you’re likely to keep using Spring and Hibernate, or other similar frameworks, in your projects built with Kotlin. And while the development tools for Kotlin itself are going to be free and open-source, the support for the enterprise development frameworks and tools will remain part of IntelliJ IDEA Ultimate, the commercial version of the IDE. And of course the framework support will be fully integrated with Kotlin.
https://blog.jetbrains.com/kotlin/2011/08/why-jetbrains-need...
Outside Android, I will care about Kotlin when KVM becomes an unavoidable reality, until then, it can party with Beanshell, jTCL, Jython, JRuby, Scala. Closjure, Groovy, Frege, and plenty of other ones,
https://en.m.wikipedia.org/wiki/List_of_JVM_languages