Inconsistency between #compareTo an isXxx comparison methods

[marschall]

Judging from the RI the contract of MonetaryAmount#compareTo seems to be to first compare by currency code (not by currency, even though CurrencyUnit is Comparable) before comparing by numeric value. However all the convenience comparison methods #isGreaterThan, #isGreaterThanOrEqualTo, #isLessThan, #isLessThanOrEqualTo, #isEqualTo are specified to throw MonetaryException if the currency code (not the currency) is different.

This leads to the following behavior:

FastMoney money = FastMoney.of(BigDecimal.valueOf(2L), CHF);

assertTrue(money.compareTo(FastMoney.of(BigDecimal.valueOf(1L), EUR)) < 0); // passes

assertTrue(money.isLessThan(FastMoney.of(BigDecimal.valueOf(1L), EUR))); // throws MonetaryException

This may be an issue with the RI and not the API, as the API gives no guidance on how #compareTo should be implemented. However the API requires that #equals considers the currency unit and that best practices are that a.equals(b) implies a.compareTo(b) == 0 .

[stokito]

A good point. Comparator can be used for example to sort some amounts in table. And that’s ok to compare amounts with different currencies. So it shouldn’t throw any exceptions for different currencies but instead it should compare by a currency firts.