Passing a Clojure function as java.util.Function

Question

As in topic, I'd like to use a Java method taking a Function as an argument and provide it with a Clojure function, be it anonymous or a regular one. Anyone has any idea how to do that?

Answer 1

Terje's accepted answer is absolutely correct. But you can make it a little easier to use with a first-order function:

(defn ^java.util.function.Function as-function [f]
  (reify java.util.function.Function
    (apply [this arg] (f arg))))

or a macro:

(defmacro jfn [& args]
  `(as-function (fn ~@args)))

Answer 2

java.util.function.Function is an interface.
You need to implement the abstract method apply(T t).
Something like this should do it:

(defn hello [name]
  (str "Hello, " name "!"))

(defn my-function[]
  (reify 
    java.util.function.Function
    (apply [this arg]
      (hello arg))))

;; then do (my-function) where you need to pass in a Function