Package org.apache.commons.rng.sampling

Class ListSampler

java.lang.Object

org.apache.commons.rng.sampling.ListSampler

public final class ListSampler
extends java.lang.Object

Sampling from a List.

This class also contains utilities for shuffling a List in-place.

Since:

1.0

Method Summary

Modifier and Type	Method	Description
static <T> java.util.List<T>	sample(org.apache.commons.rng.UniformRandomProvider rng, java.util.List<T> collection, int k)	Generates a list of size k whose entries are selected randomly, without repetition, from the items in the given collection.
static <T> void	shuffle(org.apache.commons.rng.UniformRandomProvider rng, java.util.List<T> list)	Shuffles the entries of the given array, using the Fisher-Yates algorithm.
static <T> void	shuffle(org.apache.commons.rng.UniformRandomProvider rng, java.util.List<T> list, int start, boolean towardHead)	Shuffles the entries of the given array, using the Fisher-Yates algorithm.

Methods inherited from class java.lang.Object

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

Method Detail

sample

public static <T> java.util.List<T> sample(org.apache.commons.rng.UniformRandomProvider rng,
                                           java.util.List<T> collection,
                                           int k)

Generates a list of size k whose entries are selected randomly, without repetition, from the items in the given collection.

Sampling is without replacement; but if the source collection contains identical objects, the sample may include repeats.

Sampling uses UniformRandomProvider.nextInt(int).

Type Parameters:

T - Type of the list items.

Parameters:

rng - Generator of uniformly distributed random numbers.

collection - List to be sampled from.

k - Size of the returned sample.

Returns:

a shuffled sample from the source collection.

Throws:

java.lang.IllegalArgumentException - if k <= 0 or k > collection.size().

shuffle

public static <T> void shuffle(org.apache.commons.rng.UniformRandomProvider rng,
                               java.util.List<T> list)

Shuffles the entries of the given array, using the Fisher-Yates algorithm.

Sampling uses UniformRandomProvider.nextInt(int).

Type Parameters:

T - Type of the list items.

Parameters:

rng - Random number generator.

list - List whose entries will be shuffled (in-place).

shuffle

public static <T> void shuffle(org.apache.commons.rng.UniformRandomProvider rng,
                               java.util.List<T> list,
                               int start,
                               boolean towardHead)

Shuffles the entries of the given array, using the Fisher-Yates algorithm.

The start and pos parameters select which part of the array is randomized and which is left untouched.

Sampling uses UniformRandomProvider.nextInt(int).

Type Parameters:

T - Type of the list items.

Parameters:

rng - Random number generator.

list - List whose entries will be shuffled (in-place).

start - Index at which shuffling begins.

towardHead - Shuffling is performed for index positions between start and either the end (if false) or the beginning (if true) of the array.