docs: private static String percentEncode(char c, String characterEncoding)
      {
          String app = null;
          if (c > (char)((short)0x007F))
          {
              //percent encode in the proper encoding to be consistent
              app = percentEncodeNonUsAsciiCharacter(c, characterEncoding);
          }
          else
          {
              //percent encode US-ASCII char (0x00-0x7F range)
              app = "%" + HEX_CHARSET.charAt( ((c >> 0x4) % 0x10)) +HEX_CHARSET.charAt(c % 0x10);
          }
          return app;
      }