code: static String removeExtraneousSlashes(String s) {
      int lastNonSlash = NON_SLASH_MATCHER.lastIndexIn(s);
      if (lastNonSlash != -1) {
        s = s.substring(0, lastNonSlash + 1);
      }
  
      return SLASH_MATCHER.collapseFrom(s, '/');
    }
docs: Removes extra slashes from a path.  Leading slash is preserved, trailing
  slash is stripped, and any runs of more than one slash in the middle is
  replaced by a single slash.