Package stdlib

Class StdRandom

java.lang.Object

stdlib.StdRandom

public final class StdRandom
extends Object

Standard random. This class provides methods for generating random number from various distributions.

For additional documentation, see Section 2.2 of Introduction to Programming in Java: An Interdisciplinary Approach by Robert Sedgewick and Kevin Wayne.

Field Summary

Fields

Modifier and Type	Field	Description
private static Random	random
private static long	seed

Constructor Summary

Constructors

Modifier	Constructor	Description
private	StdRandom()

Method Summary

Modifier and Type	Method	Description
static boolean	bernoulli()	Return a boolean, which is true with probability .5, and false otherwise.
static boolean	bernoulli(double p)	Return a boolean, which is true with probability p, and false otherwise.
static double	cauchy()	Return a real number with a Cauchy distribution.
static int	discrete(double[] a)	Return a number from a discrete distribution: i with probability a[i].
static double	exp(double lambda)	Return a real number from an exponential distribution with rate lambda.
static double	gaussian()	Return a real number with a standard Gaussian distribution.
static double	gaussian(double mean, double stddev)	Return a real number from a gaussian distribution with given mean and stddev
static int	geometric(double p)	Return an integer with a geometric distribution with mean 1/p.
static long	getSeed()	Get the seed of the psedurandom number generator.
static void	main(String[] args)	Unit test.
static double	pareto(double alpha)	Return a real number with a Pareto distribution with parameter alpha.
static int	poisson(double lambda)	Return an integer with a Poisson distribution with mean lambda.
static double	random()	Return real number uniformly in [0, 1).
static void	setSeed(long s)	Set the seed of the psedurandom number generator.
static void	shuffle(double[] a)	Rearrange the elements of a double array in random order.
static void	shuffle(double[] a, int lo, int hi)	Rearrange the elements of the subarray a[lo..hi] in random order.
static void	shuffle(int[] a)	Rearrange the elements of an int array in random order.
static void	shuffle(int[] a, int lo, int hi)	Rearrange the elements of the subarray a[lo..hi] in random order.
static void	shuffle(Object[] a)	Rearrange the elements of an array in random order.
static void	shuffle(Object[] a, int lo, int hi)	Rearrange the elements of the subarray a[lo..hi] in random order.
static double	uniform()	Return real number uniformly in [0, 1).
static double	uniform(double a, double b)	Return real number uniformly in [a, b).
static int	uniform(int N)	Return an integer uniformly between 0 (inclusive) and N (exclusive).
static int	uniform(int a, int b)	Return int uniformly in [a, b).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

random

private static Random random

seed

private static long seed

Constructor Details

StdRandom

private StdRandom()

Method Details

setSeed

public static void setSeed(long s)

Set the seed of the psedurandom number generator.

getSeed

public static long getSeed()

Get the seed of the psedurandom number generator.

uniform

public static double uniform()

Return real number uniformly in [0, 1).

uniform

public static int uniform(int N)

Return an integer uniformly between 0 (inclusive) and N (exclusive).

random

public static double random()

Return real number uniformly in [0, 1).

uniform

public static int uniform(int a,
 int b)

Return int uniformly in [a, b).

uniform

public static double uniform(double a,
 double b)

Return real number uniformly in [a, b).

bernoulli

public static boolean bernoulli(double p)

Return a boolean, which is true with probability p, and false otherwise.

bernoulli

public static boolean bernoulli()

Return a boolean, which is true with probability .5, and false otherwise.

gaussian

public static double gaussian()

Return a real number with a standard Gaussian distribution.

gaussian

public static double gaussian(double mean,
 double stddev)

Return a real number from a gaussian distribution with given mean and stddev

geometric

public static int geometric(double p)

Return an integer with a geometric distribution with mean 1/p.

poisson

public static int poisson(double lambda)

Return an integer with a Poisson distribution with mean lambda.

pareto

public static double pareto(double alpha)

Return a real number with a Pareto distribution with parameter alpha.

cauchy

public static double cauchy()

Return a real number with a Cauchy distribution.

discrete

public static int discrete(double[] a)

Return a number from a discrete distribution: i with probability a[i]. Precondition: array entries are nonnegative and their sum (very nearly) equals 1.0.

exp

public static double exp(double lambda)

Return a real number from an exponential distribution with rate lambda.

shuffle

public static void shuffle(Object[] a)

Rearrange the elements of an array in random order.

shuffle

public static void shuffle(double[] a)

Rearrange the elements of a double array in random order.

shuffle

public static void shuffle(int[] a)

Rearrange the elements of an int array in random order.

shuffle

public static void shuffle(Object[] a,
 int lo,
 int hi)

Rearrange the elements of the subarray a[lo..hi] in random order.

shuffle

public static void shuffle(double[] a,
 int lo,
 int hi)

Rearrange the elements of the subarray a[lo..hi] in random order.

shuffle

public static void shuffle(int[] a,
 int lo,
 int hi)

Rearrange the elements of the subarray a[lo..hi] in random order.

main

public static void main(String[] args)

Unit test.