I missed mostly three things:
1. simple data definition. Clojure has EDN, python has nice syntax as well, and javascript has json.
2. pretty print
3. succinct function definition/execution, and standard array of functional tooling (map, filter, reduce, etc)
Maybe the 3rd thing did get better with Java 8?
Both IDEA and Eclipse have had a REPL for a decade, not sure what exactly you were missing(?).