Surprising behavior w/ Clojure vs Java data structures

sessions.clj

user=> (-> {} (assoc [1 2] "vec") (assoc (java.util.ArrayList. [1 2]) "alist"))
{[1 2] "alist"}
user=> (-> #{} (conj [1 2]) (conj (java.util.ArrayList. [1 2])))
#{[1 2]}
user=> *clojure-version*
{:major 1, :minor 5, :incremental 1, :qualifier nil}

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user> (-> {} (assoc [1 2] "vec") (assoc (java.util.ArrayList. [1 2]) "alist"))
{[1 2] "alist"}
user> (-> #{} (conj [1 2]) (conj (java.util.ArrayList. [1 2])))
#{[1 2] [1 2]}
user> *clojure-version*
{:major 1, :minor 6, :incremental 0, :qualifier nil}