markdown Clojure中Java类的漂亮打印方法。在REPL中有用。

Posted 2021-05-06

(defn print-methods
  "For a class 'x', print the methods (ordered by their name) in
   the following fashion:
   
   <methodName>(<parameters if any>) -> <return value>"
  [x]
  (let [meth-seq    (-> x class .getMethods seq)
        ordered-seq (sort-by #(.getName %) meth-seq)
        params      (fn [m] 
                      (let [ptypes (.getParameterTypes m)]
                        (if (= 0 (count ptypes))
                          ""
                          (clojure.string/join ", "
                            (for [x ptypes]
                              (.getName x))))))]
    (printf "class %s\n-----------\n" (-> x class .getName))
    (doseq [m ordered-seq]
      (printf "%s(%s) -> %s\n" (.getName m) (params m) (.getReturnType m)))))

The function `print-methods` is intended to be used inside a REPL. Just copy and paste it to your REPL and enjoy:

```clojure
main=> ; paste print-methods
main=> (print-methods 1)
class java.lang.Long
-----------
bitCount(long) -> int
byteValue() -> byte
compare(long, long) -> int
;...
```