efficient clojure line counting

linecounting.clj

(import '(java.io InputStreamReader FileInputStream BufferedReader))
(import '(java.util.zip GZIPInputStream))

(defn gz-line-counter [^String file-name]
  (let [^BufferedReader reader (BufferedReader. (InputStreamReader. (GZIPInputStream. (FileInputStream. file-name))))]
    (try
      (loop [i 0]
        (if (.readLine reader)
          (recur (inc i))
          i))
      (finally
        (.close reader)))))