defrecord-deftype-print-method.clj

(defprotocol Pair (a [_]) (b [_]))

(defmethod print-method user.Pair [o w]
  (.write w (str "#<Pair[" (.getName (class o)) "] " (a o) ", " (b o) ">")))

(deftype PairType [a b]
  Pair
  (a [_] a)
  (b [_] b))

(PairType. 1 2)
;=> #<Pair[user.PairType] 1, 2>

(defrecord PairRec [a b]
  Pair
  (a [_] a)
  (b [_] b))

(remove-method print-method PairRec)
(prefer-method print-method user.Pair clojure.lang.IPersistentMap)

(PairRec. 1 2)
;=> #<Pair[user.PairRec] 1, 2>