code: private void getPath(String uri, StringBuilder builder) {
          if (pattern.length() == 0) {
              return;
          }
          String hash = getHash(uri);
          int hashPos = 0;
          for (int i = 0; i < pattern.length(); i++) {
              char c = pattern.charAt(i);
              if (c == '#') {
                  builder.append(hash.charAt(hashPos++));
              } else {
                  builder.append(c);
              }
          }
          builder.append('/');
      }
docs: gets the path based on the hash of the uri, or "" if the pattern is empty