Syntax error when passing Java static method to Clojure function args directly:
(filter Character/isUpperCase "aBcD")
Why does it want the wrapper then work?
(filter #(Character/isUpperCase %) "aBcD")
Because filter takes a Clojure function as first argument, and one or more collections as rest.
A Java method is not a Clojure function. Wrapping the method in an anonymous function makes it one.