com.soundhelix.util

Class RandomUtils

java.lang.Object

com.soundhelix.util.RandomUtils

public final class RandomUtils
extends Object

Implements some static methods for random numbers. All methods need a random generator as a parameter.

Author:

Thomas Schuerger (thomas@schuerger.com)

Method Summary

Methods

Modifier and Type	Method and Description
static boolean	getBoolean(Random random, double probability) Returns a boolean being true with the given probability.
static double	getNormalDouble(Random random, double min, double max, double mean, double variance) Returns a normally distributed random double within min and max (both inclusive), having the specified mean and the specified variance.
static int	getNormalInteger(Random random, int min, int max, double mean, double variance) Returns a normally distributed random integer within min and max (both inclusive), having the specified mean and the specified variance.
static double	getPowerDouble(double value, double min, double max, double exponent) Converts the given random value (between 0 and 1) into a double with a power distribution of the given exponent between min (inclusive) and max (exclusive).
static double	getPowerDouble(Random random, double min, double max, double exponent) Returns a random double with a power distribution of the given exponent between min (inclusive) and max (exclusive).
static double	getUniformDouble(Random random, double min, double max) Returns a random double uniformly distributed within min (inclusive) and max (exclusive). max cannot be returned by this method, but even if it could, the probability for the random value being exactly max would be negligible (in the order of 2^-53).
static double	getUniformDouble(Random random, double min, double max, double step) Returns a random double uniformly distributed within min (inclusive) and max (exclusive), using a granularity of step.
static int	getUniformInteger(Random random, int min, int max, int step) Returns a random integer uniformly distributed within min and max (both inclusive), using a granularity of step.

Methods inherited from class java.lang.Object

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

Method Detail

getUniformInteger

public static int getUniformInteger(Random random,
                    int min,
                    int max,
                    int step)

Returns a random integer uniformly distributed within min and max (both inclusive), using a granularity of step. The granularity is based on min, i.e., only values of the form min+k*step (k = 0, 1, ..., upto a suitable maximum) can be returned.

Parameters:

random - the random generator

min - the minimum value (inclusive)

max - the maximum value (inclusive)

step - the step (must be >= 0)

Returns:

a uniformly distributed integer

getUniformDouble

public static double getUniformDouble(Random random,
                      double min,
                      double max)

Returns a random double uniformly distributed within min (inclusive) and max (exclusive). max cannot be returned by this method, but even if it could, the probability for the random value being exactly max would be negligible (in the order of 2^-53).

Parameters:

random - the random generator

min - the minimum value (inclusive)

max - the maximum value (exclusive)

Returns:

a uniformly distributed integer

getUniformDouble

public static double getUniformDouble(Random random,
                      double min,
                      double max,
                      double step)

Returns a random double uniformly distributed within min (inclusive) and max (exclusive), using a granularity of step. The granularity is based on min, i.e., only values of the form min+k*step (k = 0, 1, ..., upto a suitable maximum) can be returned.

Parameters:

random - the random generator

min - the minimum value (inclusive)

max - the maximum value (exclusive)

step - the step (must be >= 0)

Returns:

a uniformly distributed double

getNormalInteger

public static int getNormalInteger(Random random,
                   int min,
                   int max,
                   double mean,
                   double variance)

Returns a normally distributed random integer within min and max (both inclusive), having the specified mean and the specified variance. If the calculated random Gaussian does not fall into the specified interval between min and max, the process is repeated until it does.

Parameters:

random - the random generator

min - the minimum value (inclusive)

max - the maximum value (inclusive)

mean - the mean value

variance - the variance (square of the standard deviation)

Returns:

a normally distributed integer

getNormalDouble

public static double getNormalDouble(Random random,
                     double min,
                     double max,
                     double mean,
                     double variance)

Returns a normally distributed random double within min and max (both inclusive), having the specified mean and the specified variance. If the calculated random Gaussian does not fall into the specified interval between min and max, the process is repeated until it does.

Parameters:

random - the random generator

min - the minimum value (inclusive)

max - the maximum value (inclusive)

mean - the mean value

variance - the variance (square of the standard deviation)

Returns:

a normally distributed double

getPowerDouble

public static double getPowerDouble(Random random,
                    double min,
                    double max,
                    double exponent)

Returns a random double with a power distribution of the given exponent between min (inclusive) and max (exclusive). A negative exponent will swap the minimum and maximum.

Parameters:

random - the random generator

min - the minimum value (inclusive)

max - the maximum value (exclusive)

exponent - the exponent (1 = linear, 2 = quadratic, 3 = cubic, -1 = reverse linear, etc.)

Returns:

the random double

getPowerDouble

public static double getPowerDouble(double value,
                    double min,
                    double max,
                    double exponent)

Converts the given random value (between 0 and 1) into a double with a power distribution of the given exponent between min (inclusive) and max (exclusive). A negative exponent will swap the minimum and maximum.

Parameters:

value - the random value (between 0 and 1)

min - the minimum value (inclusive)

max - the maximum value (exclusive)

exponent - the exponent (1 = linear, 2 = quadratic, 3 = cubic, -1 = reverse linear, etc.)

Returns:

the random double

getBoolean

public static boolean getBoolean(Random random,
                 double probability)

Returns a boolean being true with the given probability.

Parameters:

random - the random generator

probability - the probability (between 0 and 1)

Returns:

a boolean being true with the given probability