Package api.util

Class RandomSelector<T>

java.lang.Object
api.util.RandomSelector<T>
Type Parameters:
T -
public final class RandomSelector<T> extends Object
A tool to randomly select elements from collections.

Example usages: 


 Random random = ...
 Map<String, Double> stringWeights = new Hash<>();
 stringWeights.put("a", 4d);
 stringWeights.put("b", 3d);
 stringWeights.put("c", 12d);
 stringWeights.put("d", 1d);

 RandomSelector<String> selector = RandomSelector.weighted(stringWeights.keySet(), s -> stringWeights.get(s));
 List<String> selection = new ArrayList<>();
 for (int i = 0; i < 10; i++) {
   selection.add(selector.next(random));
 }

  • Method Details

    • uniform

      public static <T> RandomSelector<T> uniform(Collection<T> elements) throws IllegalArgumentException
      Creates a new random selector based on a uniform distribution.

      A copy of elements is kept, so any modification to elements will not be reflected in returned values.

      Type Parameters:
      T -
      Parameters:
      elements -
      Returns:
      Throws:
      IllegalArgumentException - if elements is empty.

    • weighted

      public static <T> RandomSelector<T> weighted(Collection<T> elements, ToDoubleFunction<? super T> weighter) throws IllegalArgumentException
      Creates a random selector among elements where the elements have a weight defined by weighter.

      A copy of elements is kept, so any modification to elements will not be reflected in returned values.

      Type Parameters:
      T -
      Parameters:
      elements -
      weighter -
      Returns:
      Throws:
      IllegalArgumentException - if elements is empty or if weighter returns a negative value or 0.

    • next

      public T next(Random random)
      Returns the next element using random.
      Parameters:
      random -
      Returns:

    • stream

      public Stream<T> stream(Random random)
      Returns a stream of elements using random. The stream must use a terminal operation to become closed and free the resources it's been using.

      Even though this instance is thread-safe and for performance reasons, it is recommended to use a different stream per thread given that Random has performance drawbacks in multi-threaded environments.

      Parameters:
      random -
      Returns: