Java Reference
In-Depth Information
B
IG
N
UMBERS
Although Java does not define a primitive data type similar to COBOL's familiar
packed decimal, Java defines two classes that are similar. These support math functions
for numbers of arbitrary (and user-defined) precision. When you use these classes in-
stead of the primitive float and double intrinsic data types, there is no requirement to
work around the precision problems of traditional floating-point arithmetic. The
Big-
Integer
class supports arbitrary precision integer arithmetic, and
BigDecimal
supports
arbitrary precision arithmetic with scale (that is, decimal positions). With Java 1.5,
BigDecimal
also supports fixed precision floating-point computation.
Both
BigInteger
and
BigDecimal
have constructors with a
String
as a parame-
ter. This is often how a
BigNumber
is initialized:
BigInteger customerNumber =
new BigInteger ("123456789012345678901234567890");
BigDecimal currencyValue =
new BigDecimal ("4.567890123456789012345");
BigDecimal customerOrder =
new BigDecimal (customerNumber, 10);
In the example,
currencyValue
will have a scale attribute (that is, the number
of digits to the right of the decimal) of 11.
customerOrder
would contain the nu-
meric value in
customerNumber
, with a scale of 10. You can also use the static
method
valueOf()
to set a
BigNumber
to a value:
BigInteger currencyValue = BigInteger.valueOf(123);
BigDecimal currencyValue = BigDecimal.valueOf(123, scale);s
These classes do come with a cost, however. Math functions using these classes
are considerably slower than math functions that use the primitive data types. An-
other inconvenience: You have to use the math functions the classes provide rather
than the native Java operators (+, -, *, /, and so forth).
