Kotlin. Its compatibility story with Java is great (although you obviously will lose some benefits such as guaranteed null-safety when interfacing with Java cod

Kotlin. Its compatibility story with Java is great (although you obviously will lose some benefits such as guaranteed null-safety when interfacing with Java code). It's multi-paradigm and supports FP well, as well as DSLs. You probably can't (or shouldn't) go as crazy with your types as in Haskell or Scala, but you do get more or less concise sum (sealed classes) and product (data classes) types, as well as generics. Plus, if you use IntelliJ, the tooling is great.