Touring Language APIs - Beginning Java 7 - page 420

Note BigInteger also declares several bit-oriented methods, such as BigIn-
teger and (BigInteger val) , BigInteger flipBit(int n) , and
BigInteger shiftLeft(int n) .Thesemethodsareusefulforwhenyouneed
to perform low-level bit manipulation.
Thebestwaytogetcomfortablewith BigInteger istotryitout. Listing4-33 uses
this class in a factorial() method comparison context.
Listing 4-33. Comparing factorial() methods
import java.math.BigInteger;
class FactComp