Question

 (ns scratch.fastflip
   (:gen-class
    :extends java.util.Random
    :implements clojure.lang.IFn))

 (defn -invoke [^java.util.Random this]
   (.next this 1))

Loading the file I get the warning:

 ;scratch.coin=> Reflection warning, /home/user/scratch/src/scratch/fastflip.clj:8 - call to next can't be resolved.
 #'scratch.fastflip/-invoke

Note I want to get rid of the warning via eliminating the reflection, not via setting warning mechanism to false.

Answer 1

If you’re on 1.3, this is probably because next takes an int, not a long, and 1 is an int. But are you sure next is what you want to call? If you’re doing coin-flipping, I would just use nextInt(2), as next looks like implementation internals.

Edit: Here’s syntax you can use to do what you want without a reflection warning.

(ns test-genclass.core
  (:gen-class
   :extends java.util.Random
   :implements [clojure.lang.IFn]
   :exposes-methods {next inner}))

(set! *warn-on-reflection* true)

(defn -invoke [^test_genclass.core this]
  (.inner this 1))

(defn -main [& args]
  ((test_genclass.core.)))