> you can swap it with Scala, Kotlin, Clojure, Haskell (Eta), Groovy, JRuby and others Only Scala and Kotlin are feasible alternatives to Java for building app

> you can swap it with Scala, Kotlin, Clojure, Haskell (Eta), Groovy, JRuby and others Only Scala and Kotlin are feasible alternatives to Java for building applications on the JVM or Android. The others in that list are limited by dynamic typing to scripting only or didn't see much adoption for building large systems, e.g. Apache Groovy for glue code and build scripts.