Clojure: working with a java.util.HashMap in an idiomatic Clojure fashion

Question

I have a java.util.HashMap object m (a return value from a call to Java code) and I\'d like to get a new map with an additional key-value pair.

Answer 1

Clojure makes the java Collections seq-able, so you can directly use the Clojure sequence functions on the java.util.HashMap.

But assoc expects a clojure.lang.Associative so you'll have to first convert the java.util.HashMap to that:

(assoc (zipmap (.keySet m) (.values m)) "key" "value")

Edit: simpler solution:

(assoc (into {} m) "key" "value")