my_file_utils.clj

(ns my-file-utils
  (:import java.io.File))

;; Java methods cannot be used as Clojure functions,
;; so you have to wrap them in functions.

;; anonymous function, map, and filter version
(defn list-files [d]
  (map (fn [f] (.getName f))
       (filter (fn [f] (.isDirectory f))
               (.listFiles d))))

;; anonymous function shorthand
(defn list-files [d]
  (map #(.getName %))
       (filter #(.isDirectory %)
               (.listFiles d))))

;; version using "threading" macros
(defn list-files
  (->> (.listFiles d)
       (filter #(.isDirectory %))
       (map #(.getName %))))

;; list comprehension version
(defn list-files [d]
  (for [f (.listFiles d)
        :when (.isDirectory f)]
    (.getName f)))

;; Usage: (prn (list-files (File. "/home/mcrittenden/Downloads")))