Some regex implementations allow for comments in the string; if your does not, you can probably make it work with concatenation, like:

  String pattern = "^https+" // match the protocol at the beginning
                 + "([a-zA-Z])+" // match the machine name
                 + ...

Honestly, I use regular expressions because, even in such format expanded with comments, I haven't seen anything more readable after you get used to regex operators. I guess the closest would be the alternative format in CL-PPCRE. For instance:

  CL-USER> (cl-ppcre:parse-string "\\b\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\b")
  (:SEQUENCE :WORD-BOUNDARY (:GREEDY-REPETITION 1 3 :DIGIT-CLASS) #\.
   (:GREEDY-REPETITION 1 3 :DIGIT-CLASS) #\.
   (:GREEDY-REPETITION 1 3 :DIGIT-CLASS) #\.
   (:GREEDY-REPETITION 1 3 :DIGIT-CLASS) :WORD-BOUNDARY)

But then, any such form can get mouthful:

  CL-USER> (cl-ppcre:parse-string "((\\b[0-9]+)?\\.)?\\b[0-9]+([eE][-+]?[0-9]+)?\\b")
  (:SEQUENCE
   (:GREEDY-REPETITION 0 1
    (:REGISTER
     (:SEQUENCE
      (:GREEDY-REPETITION 0 1
       (:REGISTER
        (:SEQUENCE :WORD-BOUNDARY
         (:GREEDY-REPETITION 1 NIL (:CHAR-CLASS (:RANGE #\0 #\9))))))
      #\.)))
   :WORD-BOUNDARY
   (:GREEDY-REPETITION 1 NIL (:CHAR-CLASS (:RANGE #\0 #\9)))
   (:GREEDY-REPETITION 0 1
    (:REGISTER
     (:SEQUENCE (:CHAR-CLASS #\e #\E)
      (:GREEDY-REPETITION 0 1 (:CHAR-CLASS #\- #\+))
      (:GREEDY-REPETITION 1 NIL (:CHAR-CLASS (:RANGE #\0 #\9))))))
   :WORD-BOUNDARY)