code: private static void printCodePointAsTwoHexDigits(Appendable out, int c)
          throws IOException
      {
          String s = Integer.toHexString(c);
          out.append("\\x");
          if (s.length() < 2) {
              out.append(ZERO_PADDING[2-s.length()]);
          }
          out.append(s);
      }
docs: Generates a two-digit hex escape sequence,
  {@code "\x}<i>{@code HH}</i>{@code "},
  using lower-case for alphabetics.