May I suggest Kawa (https://www.gnu.org/software/kawa) if you're open to Lisp-style syntax (Kawa is a Scheme dialect)? Kawa has great Java interoperability, Java-like performance (with the help of optional type declarations), a nice REPL, full documentation, maturity (continuous development since 1996), and many neat features. It doesn't require special tools or workflow. (I do suggest using the git version, as it is overdue for a release.)