code: protected final void registerCurrency(String currencyCode, int numericCurrencyCode, int decimalPlaces) {
          CurrencyUnit.registerCurrency(currencyCode, numericCurrencyCode, decimalPlaces, true);
      }
docs: Registers a currency allowing it to be used.
  <p>
  This method is called by {@link #registerCurrencies()} to perform the
  actual creation of a currency.
  
  @param currencyCode  the currency code, not null
  @param numericCurrencyCode  the numeric currency code, -1 if none
  @param decimalPlaces  the number of decimal places that the currency
  normally has, from 0 to 3, or -1 for a pseudo-currency