Class CollectionSampler<T>

java.lang.Object

org.apache.commons.rng.sampling.CollectionSampler<T>

Type Parameters:

T - Type of items in the collection.

All Implemented Interfaces:

ObjectSampler<T>, SharedStateObjectSampler<T>, SharedStateSampler<SharedStateObjectSampler<T>>

public class CollectionSampler<T>
extends Object
implements SharedStateObjectSampler<T>

Sampling from a Collection.

Sampling uses UniformRandomProvider.nextInt(int).

Since:

1.0

Field Summary

Fields

Modifier and Type	Field	Description
private final List<T>	items	Collection to be sampled from.
private final UniformRandomProvider	rng	RNG.

Constructor Summary

Constructors

Modifier	Constructor	Description
	CollectionSampler(UniformRandomProvider rng, Collection<T> collection)	Creates a sampler.
private	CollectionSampler(UniformRandomProvider rng, List<T> collection)

Method Summary

Modifier and Type	Method	Description
T	sample()	Picks one of the items from the collection passed to the constructor.
private static <T> List<T>	toList(Collection<T> collection)	Convert the collection to a list (shallow) copy.
CollectionSampler<T>	withUniformRandomProvider(UniformRandomProvider rng)	Create a new instance of the sampler with the same underlying state using the given uniform random provider as the source of randomness.

Methods inherited from class Object

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

Methods inherited from interface ObjectSampler

samples, samples

Field Details

items

private final List<T> items

Collection to be sampled from.

rng

private final UniformRandomProvider rng

RNG.

Constructor Details

CollectionSampler

public CollectionSampler(UniformRandomProvider rng,
 Collection<T> collection)

Creates a sampler.

Parameters:

rng - Generator of uniformly distributed random numbers.

collection - Collection to be sampled. A (shallow) copy will be stored in the created instance.

Throws:

IllegalArgumentException - if collection is empty.

CollectionSampler

private CollectionSampler(UniformRandomProvider rng,
 List<T> collection)

Parameters:

rng - Generator of uniformly distributed random numbers.

collection - Collection to be sampled.

Method Details

sample

public T sample()

Picks one of the items from the collection passed to the constructor.

Specified by:

sample in interface ObjectSampler<T>

Returns:

a random sample.

withUniformRandomProvider

public CollectionSampler<T> withUniformRandomProvider(UniformRandomProvider rng)

Create a new instance of the sampler with the same underlying state using the given uniform random provider as the source of randomness.

Specified by:

withUniformRandomProvider in interface SharedStateSampler<T>

Parameters:

rng - Generator of uniformly distributed random numbers.

Returns:

the sampler

Since:

1.3

toList

private static <T> List<T> toList(Collection<T> collection)

Convert the collection to a list (shallow) copy.

This method exists to raise an exception before invocation of the private constructor; this mitigates Finalizer attacks (see SpotBugs CT_CONSTRUCTOR_THROW).

Type Parameters:

T - Type of items in the collection.

Parameters:

collection - Collection.

Returns:

the list copy

Throws:

IllegalArgumentException - if collection is empty.