code: public void readHex() {
          if (pos < s.length()
              && ((s.charAt(pos) >= '0' && s.charAt(pos) <= '9')
                  || (s.charAt(pos) >= 'A' && s.charAt(pos) <= 'F')
                  || (s.charAt(pos) >= 'a' && s.charAt(pos) <= 'f'))) {
              pos++;
          } else {
              throw new JSONParseException(s, pos);
          }
      }
docs: Read the current character, making sure that it is a hexidecimal character.
  
  @throws JSONParseException if the current character is not a hexidecimal character