code: public static String normalise(String ensName) {
          try {
              return IDN.toASCII(ensName, IDN.USE_STD3_ASCII_RULES)
                      .toLowerCase();
          } catch (IllegalArgumentException e) {
              throw new EnsResolutionException("Invalid ENS name provided: " + ensName);
          }
      }
docs: Normalise ENS name as per the
  <a href="http://docs.ens.domains/en/latest/implementers.html#normalising-and-validating-names">specification</a>.
  
  @param ensName our user input ENS name
  @return normalised ens name
  @throws EnsResolutionException if the name cannot be normalised