code: public static CurrencyUnit ofCountry(String countryCode) {
          MoneyUtils.checkNotNull(countryCode, "Country code must not be null");
          CurrencyUnit currency = currenciesByCountry.get(countryCode);
          if (currency == null) {
              throw new IllegalCurrencyException("No currency found for country '" + countryCode + '\'');
          }
          return currency;
      }
docs: Obtains an instance of {@code CurrencyUnit} for the specified ISO-3166 country code.
  <p>
  Country codes should generally be in upper case.
  This method is case sensitive.
  
  @param countryCode  the country code, typically ISO-3166, not null
  @return the singleton instance, never null
  @throws IllegalCurrencyException if the currency is unknown