```clojure
(ns caesium.util
  "Internal utilities.

  This ns is not considered public API, and may break without semver
  major version increments."
  (:import (java.util Arrays)
           (org.apache.commons.codec.binary Hex)))

(defn unhexify
  [^String s]
  (.decode (Hex.) (.getBytes s)))

(defn hexify
  [b]
  (Hex/encodeHexString b))

(defn n->bytes
  "Turns n into a byte array of length len."
  [len n]
  (let [unpadded (.toByteArray (biginteger n))
        bytelen (alength unpadded)
        output (byte-array len)]
    (System/arraycopy unpadded 0 output (- len bytelen) bytelen)
    output))
```

Fix a reflection warning on a static method argument type
user
```clojure
(ns caesium.util
  "Internal utilities.

  This ns is not considered public API, and may break without semver
  major version increments."
  (:import (java.util Arrays)
           (org.apache.commons.codec.binary Hex)))

(defn unhexify
  [^String s]
  (.decode (Hex.) (.getBytes s)))

(defn hexify
  [^bytes b]
  (Hex/encodeHexString b))

(defn n->bytes
  "Turns n into a byte array of length len."
  [len n]
  (let [unpadded (.toByteArray (biginteger n))
        bytelen (alength unpadded)
        output (byte-array len)]
    (System/arraycopy unpadded 0 output (- len bytelen) bytelen)
    output))
```
assistant