java.math
Class BigInteger
- Comparable<T>, Serializable
Written using on-line Java Platform 1.2 API Specification, as well
as "The Java Class Libraries", 2nd edition (Addison-Wesley, 1998) and
"Applied Cryptography, Second Edition" by Bruce Schneier (Wiley, 1996).
Based primarily on IntNum.java BitOps.java by Per Bothner (per@bothner.com)
(found in Kawa 1.6.62).
clone , equals , extends Object> getClass , finalize , hashCode , notify , notifyAll , toString , wait , wait , wait |
ONE
public static final BigInteger ONE
The constant one as a BigInteger.
TEN
public static final BigInteger TEN
The constant ten as a BigInteger.
ZERO
public static final BigInteger ZERO
The constant zero as a BigInteger.
BigInteger
public BigInteger(int signum,
byte[] magnitude)
bitCount
public int bitCount()
Count one bits in a BigInteger.
If argument is negative, count zero bits instead.
bitLength
public int bitLength()
Calculates ceiling(log2(this <320 ? -this : this+1))
See Common Lisp: the Language, 2nd ed, p. 361.
equals
public boolean equals(Object obj)
Determine whether this Object is semantically equal
to another Object.
There are some fairly strict requirements on this
method which subclasses must follow:
- It must be transitive. If
a.equals(b)
and
b.equals(c)
, then a.equals(c)
must be true as well. - It must be symmetric.
a.equals(b)
and
b.equals(a)
must have the same value. - It must be reflexive.
a.equals(a)
must
always be true. - It must be consistent. Whichever value a.equals(b)
returns on the first invocation must be the value
returned on all later invocations.
a.equals(null)
must be false.- It must be consistent with hashCode(). That is,
a.equals(b)
must imply
a.hashCode() == b.hashCode()
.
The reverse is not true; two objects that are not
equal may have the same hashcode, but that has
the potential to harm hashing performance.
This is typically overridden to throw a
ClassCastException
if the argument is not comparable to the class performing
the comparison, but that is not a requirement. It is legal
for
a.equals(b)
to be true even though
a.getClass() != b.getClass()
. Also, it
is typical to never cause a
NullPointerException
.
In general, the Collections API (
java.util
) use the
equals
method rather than the
==
operator to compare objects. However,
IdentityHashMap
is an exception to this rule, for its own good reasons.
The default implementation returns
this == o
.
- equals in interface Object
obj
- the Object to compare to
- whether this Object is semantically equal to another
hashCode
public int hashCode()
Get a value that represents this Object, as uniquely as
possible within the confines of an int.
There are some requirements on this method which
subclasses must follow:
- Semantic equality implies identical hashcodes. In other
words, if
a.equals(b)
is true, then
a.hashCode() == b.hashCode()
must be as well.
However, the reverse is not necessarily true, and two
objects may have the same hashcode without being equal. - It must be consistent. Whichever value o.hashCode()
returns on the first invocation must be the value
returned on all later invocations as long as the object
exists. Notice, however, that the result of hashCode may
change between separate executions of a Virtual Machine,
because it is not invoked on the same object.
Notice that since
hashCode
is used in
Hashtable
and other hashing classes,
a poor implementation will degrade the performance of hashing
(so don't blindly implement it as returning a constant!). Also,
if calculating the hash is time-consuming, a class may consider
caching the results.
The default implementation returns
System.identityHashCode(this)
- hashCode in interface Object
- the hash code for this Object
isProbablePrime
public boolean isProbablePrime(int certainty)
Returns true
if this BigInteger is probably prime,
false
if it's definitely composite. If certainty
is <= 0
, true
is returned.
certainty
- a measure of the uncertainty that the caller is willing
to tolerate: if the call returns true
the probability that
this BigInteger is prime exceeds (1 - 1/2certainty)
.
The execution time of this method is proportional to the value of this
parameter.
true
if this BigInteger is probably prime,
false
if it's definitely composite.
not
public BigInteger not()
Return the logical (bit-wise) negation of a BigInteger.
pow
public BigInteger pow(int exponent)
Calculate the integral power of a BigInteger.
exponent
- the exponent (must be non-negative)
probablePrime
public static BigInteger probablePrime(int bitLength,
Random rnd)
Return a BigInteger that is bitLength bits long with a
probability <322^-100 of being composite.
bitLength
- length in bits of resulting numberrnd
- random number generator to use
testBit
public boolean testBit(int n)
toString
public String toString()
Convert this Object to a human-readable String.
There are no limits placed on how long this String
should be or what it should contain. We suggest you
make it as intuitive as possible to be able to place
it into
System.out.println()
and such.
It is typical, but not required, to ensure that this method
never completes abruptly with a
RuntimeException
.
This method will be called when performing string
concatenation with this object. If the result is
null
, string concatenation will instead
use
"null"
.
The default implementation returns
getClass().getName() + "@" +
Integer.toHexString(hashCode())
.
- toString in interface Object
- the String representing this Object, which may be null
valueOf
public static BigInteger valueOf(long val)
Return a (possibly-shared) BigInteger with a given long value.
java.math.BigInteger -- Arbitary precision integers
Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2005, 2006, 2007, 2010
Free Software Foundation, Inc.
This file is part of GNU Classpath.
GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
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02110-1301 USA.
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