make j.u.Collections print-readably (pr, prn) like their Clojure variants, print* and *print-dup* behavior unchanged

Author: richhickey

src/clj/clojure/core_print.clj

@@ -87,13 +87,16 @@
   (print-args o w)
   (.write w ")"))
 
-(defmethod print-method Object [o, ^Writer w]
+(defn- print-object [o, ^Writer w]
   (.write w "#<")
   (.write w (.getSimpleName (class o)))
   (.write w " ")
   (.write w (str o))
   (.write w ">"))
 
+(defmethod print-method Object [o, ^Writer w]
+  (print-object o w))
+
 (defmethod print-method clojure.lang.Keyword [o, ^Writer w]
   (.write w (str o)))
 
@@ -214,6 +217,40 @@
   (print-map m print-dup w)
   (.write w ")"))
 
+;; java.util
+(prefer-method print-method clojure.lang.IPersistentCollection java.util.Collection)
+(prefer-method print-method clojure.lang.IPersistentCollection java.util.RandomAccess)
+(prefer-method print-method java.util.RandomAccess java.util.List)
+(prefer-method print-method clojure.lang.IPersistentCollection java.util.Map)
+
+(defmethod print-method java.util.List [c, ^Writer w]
+  (if *print-readably*
+    (do
+      (print-meta c w)
+      (print-sequential "(" pr-on " " ")" c w))
+    (print-object c w)))
+
+(defmethod print-method java.util.RandomAccess [v, ^Writer w]
+  (if *print-readably*
+    (do
+      (print-meta v w)
+      (print-sequential "[" pr-on " " "]" v w))
+    (print-object v w)))
+
+(defmethod print-method java.util.Map [m, ^Writer w]
+  (if *print-readably*
+    (do
+      (print-meta m w)
+      (print-map m pr-on w))
+    (print-object m w)))
+
+(defmethod print-method java.util.Set [s, ^Writer w]
+  (if *print-readably*
+    (do
+      (print-meta s w)
+      (print-sequential "#{" pr-on " " "}" (seq s) w))
+    (print-object s w)))
+
 ;; Records
 
 (defmethod print-method clojure.lang.IRecord [r, ^Writer w]
@@ -241,7 +278,7 @@
   (print-meta s w)
   (print-sequential "#{" pr-on " " "}" (seq s) w))
 
-(def ^{:tag String 
+(def ^{:tag String
        :doc "Returns name string for char or nil if none"
        :added "1.0"} 
  char-name-string