Java Reference
In-Depth Information
7.257415615307994E306
7257415615307998967396728211129263114716991681296451376543577798900561843401706157852350749242617459511490991237838520776666022565442753025328900773207510902400430280058295603966612599658257104398558294257568966313439612262571094946806711205568880457193340212661452800000000000000000000000000000000000000000
1.5511210043330986E25
15511210043330985984000000
Thefirstthreevaluesrepresentthehighestfactorialsthatcanbereturnedbythe
int
-
based,
long
-based, and
double
-based
factorial()
methods. The fourth value
represents the
BigInteger
equivalent of the highest
double
factorial.
Noticethatthe
double
methodfailstoaccuratelyrepresent170!(!isthemathsym-
bol for factorial). Its precision is simply too small. Although the method attempts to
roundthesmallestdigit,roundingdoesnotalwayswork—thenumberendsin7994in-
stead of 7998. Rounding is only accurate up to argument 25.0, as the last two output
lines reveal.
Note
RSA encryption,
BigDecimal
, and factorial are practical examples of
BigInteger
's usefulness. However, you can also use
BigInteger
in unusual
ways.Forexample,myFebruary2006
JavaWorld
articletitled“TravelThroughTime
with Java” (
http://www.javaworld.com/javaworld/jw-02-2006/
jw-0213-funandgames.html
)
, a part of my Java Fun and Games series, used
BigInteger
to store an image as a very large integer. The idea was to experiment
with
BigInteger
methodstolookforimages(possiblybydiscoveringmathematical
patterns)ofpeopleandplacesthatexistedinthepast,willexistinthefuture,ormight
never exist. If this craziness appeals to you, check out my article.
EXERCISES
The following exercises are designed to test your understanding of Java's language
APIs:
1. A
prime number
is a positive integer greater than 1 that is evenly divisible
by 1 and itself. Create a
PrimeNumberTest
application that determines
ifitssolitaryintegerargumentisprimeornotprime,andoutputsasuitable
message. For example,
java PrimeNumberTest 289
should output
themessage
289 is not prime
.Asimplewaytocheckforprimality
is to loop from 2 through the square root of the integer argument, and use
the remainder operator in the loop to determine if the argument is divided
