Re: Financial operation [Hibernate]
On Nov 21, 2:16 pm, Mark Thornton <mark.p.thorn...@ntl-spam-world.com>
wrote:
Mark Space wrote:
GG wrote:
1. Mapping to BigDecimal
Use this.
2. Maping to Double
Never double. Doubles are not accurate. Ten cents is 0.10 and that is
an infinite repeating number in binary. You will get very strange
effects when using this.
Never never use any sort of double when dealing with money.
I do it all the time and it works just fine. As the values I deal with
are estimated costs based on the expected time to complete an operation
(and other factors), the question of the rounding of the final result is
irrelevant. Doubles can also represent integers exactly up to 2^53, so
you can work in cents in the same way as you might with long. It will
work with your petrol (gasoline) prices too (with far more accuracy than
any known gas pump).
If you are doing accounts or tax returns and the like, then sure use
BigDecimal. Otherwise double can be a very appropriate choice.
The key realization here is that an estimate already has some
(possibly unknown) degree of error, and the additional error
introduced by using floating-point arithmetic is not going to matter
(much). Doubles are fine for estimates and predictions and other
error-ful calculations. On the other hand, tax calculations,
accounting, and other purely financial processes often have specific
precision requirements and rounding rules that must be obeyed; the
only way to reliably get that right is to use a decimal type.
Cheers,
Owen