class MultipleCurrencyAmount implements ImmutableBean,
    Iterable<CurrencyAmount>, Serializable {

  public double getAmount(final Currency currency) {
    CurrencyAmount currencyAmount = getCurrencyAmount(currency);
    if (currencyAmount == null) {
      throw new IllegalArgumentException("Do not have an amount with currency " + currency);
    }
    return currencyAmount.getAmount();
  }

  private  MultipleCurrencyAmount(ImmutableSortedMap<Currency, CurrencyAmount> currencyAmountMap);
  private  MultipleCurrencyAmount(
      SortedMap<Currency, CurrencyAmount> currencyAmountMap);

}