Java Reference
In-Depth Information
• Because
StrictMath
cannot utilize platform-specific features such as an
extended-precision math coprocessor, an implementation of
StrictMath
might be less efficient than an implementation of
Math
.
Forthemostpart,
Math
'smethodscalltheir
StrictMath
counterparts.Twoexcep-
tions are
toDegrees()
and
toRadians()
. Although these methods have identic-
alcodebodiesinbothclasses,
StrictMath
'simplementationsincludereservedword
strictfp
in the method headers:
public static strictfp double toDegrees(double angrad)
public static strictfp double toRadians(double angdeg)
Wikipedia's“strictfp”entry(
http://en.wikipedia.org/wiki/Strictfp
)
mentionsthat
strictfp
restrictsfloating-pointcalculationstoensureportability.This
reservedwordaccomplishesportabilityinthecontextofintermediatefloating-pointrep-
resentationsandoverflows/underflows(generatingavaluetoolargeorsmalltofitarep-
resentation).
Note
The previously cited “strictfp” article states that
Math
contains
public
static strictfp double abs(double);
andother
strictfp
methods.If
youcheckoutthisclass'ssourcecodeunderJava7,youwillnotfind
strictfp
any-
where in the source code. However, many
Math
methods (such as
sin()
) call their
StrictMath
counterparts,whichareimplementedinaplatform-specificlibrary,and
the library's method implementations are strict.
Without
strictfp
,anintermediatecalculationisnotlimitedtotheIEEE75432-bit
and64-bitfloating-pointrepresentationsthatJavasupports.Instead,thecalculationcan
takeadvantageofalargerrepresentation(perhaps128bits)onaplatformthatsupports
this representation.
Anintermediatecalculationthatoverflows/underflowswhenitsvalueisrepresented
in32/64bitsmightnotoverflow/underflowwhenitsvalueisrepresentedinmorebits.
Becauseofthisdiscrepancy,portabilityiscompromised.
strictfp
levelstheplaying
field by requiring all platforms to use 32/64 bits for intermediate calculations.
When applied to a method,
strictfp
ensures that all floating-point calculations
performed in that method are in strict compliance. However,
strictfp
can be used
inaclassheaderdeclaration(asin
public strictfp class FourierTrans-
form
) to ensure that all floating-point calculations performed in that class are strict.
Note
Math
and
StrictMath
are declared
final
so that they cannot be exten-
ded.Also,theydeclare private empty noargument constructors sothat theycannot be
