code: private static void encode(char c, StringBuilder b)
     {
        b.append("_x");
        String hex = Integer.toHexString(c);
        b.append(PADDING, 0, 4 - hex.length());
        b.append(hex);
        b.append("_");
     }
docs: Encodes the character <code>c</code> as a String in the following form:
  <code>"_x" + hex value of c + "_"</code>. Where the hex value has four digits if the character
  with possibly leading zeros. <br> Example: ' ' (the space character) is encoded to: _x0020_
  
  @param c
  the character to encode
  @param b
  the encoded character is appended to <code>StringBuilder</code> <code>b</code>.