Class MersenneTwister
 All Implemented Interfaces:
Serializable
,RandomGenerator
Caveat: It is recommended to use one of WELL generators rather than the MersenneTwister generator (see this paper for more information).
This generator features an extremely long period (2^{19937}1) and 623dimensional equidistribution up to 32 bits accuracy. The home page for this generator is located at http://www.math.sci.hiroshimau.ac.jp/~mmat/MT/emt.html.
This generator is described in a paper by Makoto Matsumoto and Takuji Nishimura in 1998: Mersenne Twister: A 623Dimensionally Equidistributed Uniform PseudoRandom Number Generator, ACM Transactions on Modeling and Computer Simulation, Vol. 8, No. 1, January 1998, pp 330.
This class is mainly a Java port of the 20020126 version of the generator written in C by Makoto Matsumoto and Takuji Nishimura. Here is their original copyright:
Copyright (C) 1997  2002, Makoto Matsumoto and Takuji Nishimura, All rights reserved.
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
 Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
 Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
 The names of its contributors may not be used to endorse or promote products derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 See Also:

Constructor Summary
ConstructorDescriptionCreates a new random number generator.MersenneTwister
(int seed) Creates a new random number generator using a single int seed.MersenneTwister
(int[] seed) Creates a new random number generator using an int array seed.MersenneTwister
(long seed) Creates a new random number generator using a single long seed. 
Method Summary
Modifier and TypeMethodDescriptionprotected void
Clears the cache used by the default implementation ofRandomGenerator.nextGaussian()
.boolean
Returns the next pseudorandom, uniformly distributedboolean
value from this random number generator's sequence.void
nextBytes
(byte[] bytes) Generates random bytes and places them into a usersupplied byte array.void
nextBytes
(byte[] bytes, int start, int len) Generates random bytes and places them into a usersupplied byte array.double
Returns the next pseudorandom, uniformly distributeddouble
value between0.0
and1.0
from this random number generator's sequence.float
Returns the next pseudorandom, uniformly distributedfloat
value between0.0
and1.0
from this random number generator's sequence.double
Returns the next pseudorandom, Gaussian ("normally") distributeddouble
value with mean0.0
and standard deviation1.0
from this random number generator's sequence.int
nextInt()
Returns the next pseudorandom, uniformly distributedint
value from this random number generator's sequence.int
nextInt
(int n) Returns a pseudorandom, uniformly distributedint
value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence.long
nextLong()
Returns the next pseudorandom, uniformly distributedlong
value from this random number generator's sequence.long
nextLong
(long n) Returns a pseudorandom, uniformly distributedint
value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence.void
setSeed
(int seed) Reinitialize the generator as if just built with the given int seed.void
setSeed
(int[] seed) Reinitialize the generator as if just built with the given int array seed.void
setSeed
(long seed) Sets the seed of the underlying random number generator using along
seed.toString()

Constructor Details

MersenneTwister
public MersenneTwister()Creates a new random number generator.The instance is initialized using the current time plus the system identity hash code of this instance as the seed.

MersenneTwister
public MersenneTwister(int seed) Creates a new random number generator using a single int seed. Parameters:
seed
 the initial seed (32 bits integer)

MersenneTwister
public MersenneTwister(int[] seed) Creates a new random number generator using an int array seed. Parameters:
seed
 the initial seed (32 bits integers array), if null the seed of the generator will be related to the current time

MersenneTwister
public MersenneTwister(long seed) Creates a new random number generator using a single long seed. Parameters:
seed
 the initial seed (64 bits integer)


Method Details

setSeed
public void setSeed(int seed) Reinitialize the generator as if just built with the given int seed.The state of the generator is exactly the same as a new generator built with the same seed.
 Specified by:
setSeed
in interfaceRandomGenerator
 Parameters:
seed
 the initial seed (32 bits integer)

setSeed
public void setSeed(int[] seed) Reinitialize the generator as if just built with the given int array seed.The state of the generator is exactly the same as a new generator built with the same seed.
 Specified by:
setSeed
in interfaceRandomGenerator
 Parameters:
seed
 the initial seed (32 bits integers array), if null the seed of the generator will be the current system time plus the system identity hash code of this instance

nextInt
public int nextInt()Returns the next pseudorandom, uniformly distributedint
value from this random number generator's sequence.All 2^{32} possible
int
values should be produced with (approximately) equal probability. Specified by:
nextInt
in interfaceRandomGenerator
 Returns:
 the next pseudorandom, uniformly distributed
int
value from this random number generator's sequence

nextBoolean
public boolean nextBoolean()Returns the next pseudorandom, uniformly distributedboolean
value from this random number generator's sequence. Returns:
 the next pseudorandom, uniformly distributed
boolean
value from this random number generator's sequence

nextDouble
public double nextDouble()Returns the next pseudorandom, uniformly distributeddouble
value between0.0
and1.0
from this random number generator's sequence. Returns:
 the next pseudorandom, uniformly distributed
double
value between0.0
and1.0
from this random number generator's sequence

nextFloat
public float nextFloat()Returns the next pseudorandom, uniformly distributedfloat
value between0.0
and1.0
from this random number generator's sequence. Returns:
 the next pseudorandom, uniformly distributed
float
value between0.0
and1.0
from this random number generator's sequence

nextLong
public long nextLong()Returns the next pseudorandom, uniformly distributedlong
value from this random number generator's sequence. All 2^{64} possiblelong
values should be produced with (approximately) equal probability. Returns:
 the next pseudorandom, uniformly distributed
long
value from this random number generator's sequence

nextBytes
public void nextBytes(byte[] bytes) Generates random bytes and places them into a usersupplied byte array. The number of random bytes produced is equal to the length of the byte array. Parameters:
bytes
 the nonnull byte array in which to put the random bytes

nextBytes
public void nextBytes(byte[] bytes, int start, int len) Generates random bytes and places them into a usersupplied byte array. Parameters:
bytes
 the nonnull byte array in which to put the random bytesstart
 the starting index for inserting the generated bytes into the arraylen
 the number of bytes to generate

setSeed
public void setSeed(long seed) Sets the seed of the underlying random number generator using along
seed.Sequences of values generated starting with the same seeds should be identical.
 Specified by:
setSeed
in interfaceRandomGenerator
 Parameters:
seed
 the seed value

nextInt
Returns a pseudorandom, uniformly distributedint
value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence. Specified by:
nextInt
in interfaceRandomGenerator
 Parameters:
n
 the bound on the random number to be returned. Must be positive. Returns:
 a pseudorandom, uniformly distributed
int
value between 0 (inclusive) and n (exclusive).  Throws:
IllegalArgumentException
 if n is not positive.

nextLong
public long nextLong(long n) Returns a pseudorandom, uniformly distributedint
value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence. Specified by:
nextLong
in interfaceRandomGenerator
 Parameters:
n
 the bound on the random number to be returned. Must be positive. Returns:
 a pseudorandom, uniformly distributed
int
value between 0 (inclusive) and n (exclusive).

nextGaussian
public double nextGaussian()Returns the next pseudorandom, Gaussian ("normally") distributeddouble
value with mean0.0
and standard deviation1.0
from this random number generator's sequence. Specified by:
nextGaussian
in interfaceRandomGenerator
 Returns:
 the next pseudorandom, Gaussian ("normally") distributed
double
value with mean0.0
and standard deviation1.0
from this random number generator's sequence

clearCache
protected void clearCache()Clears the cache used by the default implementation ofRandomGenerator.nextGaussian()
. 
toString
