Package org.apache.commons.rng.sampling

Class ListSampler

java.lang.Object
org.apache.commons.rng.sampling.ListSampler
public 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​(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​(UniformRandomProvider rng, java.util.List<T> list)
    Shuffles the entries of the given array.
    static <T> void shuffle​(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 Details

    • sample

      public static <T> java.util.List<T> sample​(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​(UniformRandomProvider rng, java.util.List<T> list)
      Shuffles the entries of the given array.
      Type Parameters:
      T - Type of the list items.
      Parameters:
      rng - Random number generator.
      list - List whose entries will be shuffled (in-place).
      See Also:
      shuffle(UniformRandomProvider,List,int,boolean)

    • shuffle

      public static <T> void shuffle​(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.