reduce-kv.clj

(reduce (fn [m [k v]] (assoc m k v)) {} (doto (java.util.HashMap.) (.put "a" 1) (.put "b" 2)))
; => {"a" 1, "b" 2}

(reduce-kv (fn [m k v] (assoc m k v)) {} (doto (java.util.HashMap.) (.put "a" 1) (.put "b" 2)))
; #<IllegalArgumentException java.lang.IllegalArgumentException: No implementation of method: :kv-reduce of protocol: #'clojure.core.protocols/IKVReduce found for class: java.util.HashMap> 

(into {} (doto (java.util.HashMap.) (.put "a" 1) (.put "b" 2)))
; => {"b" 2, "a" 1}