Scala has an excellent REPL too. I often use it to test Java libraries without having to setup a full project. There is also the excellent 3rd-party REPL called Ammonite[1], which is maintained by Li Haoyi[2]. Not only is it a REPL, but it also provides a full-blown scripting interface in Scala!

[1]: http://www.lihaoyi.com/Ammonite/#Ammonite-REPL

[2]: https://github.com/lihaoyi