private void assertSameCurrencyAs(Money m) {
if (currency.equals(m.currency)) return;
throw new RuntimeException("Not same currency: " + currency + " <> " + m.currency);
}
public boolean equals(Money other) {
return currency.equals(other.currency) && (amount == other.amount);
}
boolean hasSameCurrencyAs(Money arg) {
return currency.equals(arg.currency);
}