docs: public String asHex() throws IOException {
          byte[] bytes = asByteArray();
          char[] hex = new char[bytes.length * 2];
          for ( int j = 0; j < bytes.length; j++ ) {
              int v = bytes[j] & 0xFF;
              hex[j * 2] = HEX_ARRAY[v >>> 4];
              hex[j * 2 + 1] = HEX_ARRAY[v & 0x0F];
          }
          return new String(hex);
      }