I working on different web-services, and I always use WSDL First.
JAXB generates for a Type like:
<xsd:simpleType name="CurrencyFormatTyp">
<xsd:restriction base="xsd:decimal">
<xsd:totalDigits value="13"/>
<xsd:fractionDigits value="2"/>
<xsd:minInclusive value="0.01"/>
</xsd:restriction>
</xsd:simpleType>
a Java binding type BigDecimal
(as it's mentioned in JAXB specification).
When I then do some simple arithmetic operation with values of the type double
(which are stored in a database and mapped via hibernate to the type double) I run into trouble.
<ns5:charge>0.200000000000000011102230246251565404236316680908203125</ns5:charge>
<ns5:addcharge>0.0360000000000000042188474935755948536098003387451171875</ns5:addcharge>
<ns5:tax>0.047199999999999998900879205621095024980604648590087890625</ns5:tax>
<ns5:totalextax>0.2360000000000000153210777398271602578461170196533203125</ns5:totalextax>
What would be the right way?
BigDecimal
to double
)double
to Bigdecimal
and do all my arithmetic operations in one object type.
You don't ever want to use floating point formats (such as double
and float
in Java) for currency operations, because they have limited precision and have been designed to hold values that are somehow derived from measuring (in which case they aren't absolutely precise to begin with, in which case the limited precision is less of a problem).
What Every Computer Scientist Should Know About Floating-Point Arithmetic is the article on the topic. It's a bit heavy on math, but it really helps to understand that (Alternatively, the article linked to by Michael Borgwardt is much easier to understand and still demonstrates/explains the problem).
To avoid this kind of problems, make sure that you use BigDecimal
exclusively in your code and that all external storage/transfer points use fixed-point/arbitrary-precision values as well (i.e. your database shouldn't store floating point numbers either).
double
or float
for money amountsBigDecimal
instead, that's exactly what it's forIf you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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