byte[] quad = textToNumericFormatV4(dottedQuad);
    if (quad == null) {
      return null;
    }
    String penultimate = Integer.toHexString(((quad[0] & 0xff) << 8) | (quad[1] & 0xff));
    String ultimate = Integer.toHexString(((quad[2] & 0xff) << 8) | (quad[3] & 0xff));
    return initialPart + penultimate + ":" + ultimate;
  }

  private static byte parseOctet(String ipString, int start, int end) {

    }
  }

  @J2ktIncompatible // hexadecimal doubles
  @GwtIncompatible // Doubles.tryParse
  public void testTryParseOfToHexStringIsOriginal() {
    for (double d : NUMBERS) {
      checkTryParse(d, Double.toHexString(d));
    }
  }

  @GwtIncompatible // Doubles.tryParse
  public void testTryParseNaN() {
    checkTryParse("NaN");
    checkTryParse("+NaN");
    checkTryParse("-NaN");
  }

      if (ch > Ascii.MAX) {
        throw new DecodingException("Unrecognized character: 0x" + Integer.toHexString(ch));
      }
      int result = decodabet[ch];
      if (result == -1) {
        if (ch <= 0x20 || ch == Ascii.MAX) {
          throw new DecodingException("Unrecognized character: 0x" + Integer.toHexString(ch));
        } else {
          throw new DecodingException("Unrecognized character: " + ch);
        }

     * character.</p>
     *
     * @param ch The character to convert.
     * @return An upper case hexadecimal <code>String</code>
     */
    protected static String hex(char ch) {
        return Integer.toHexString(ch).toUpperCase(Locale.ENGLISH);
    }

    /**
     * <p>Checks if the value is in the given array.</p>
     *
     * <p>The method returns <code>false</code> if a <code>null</code> array is passed in.</p>

     * character.</p>
     *
     * @param ch The character to convert.
     * @return An upper case hexadecimal <code>String</code>
     */
    protected static String hex(char ch) {
        return Integer.toHexString(ch).toUpperCase(Locale.ENGLISH);
    }

    /**
     * <p>Checks if the value is in the given array.</p>
     *
     * <p>The method returns <code>false</code> if a <code>null</code> array is passed in.</p>