org.planx.msd.util
Class NullDiscriminator<T>

java.lang.Object
  org.planx.msd.util.AbstractDiscriminator<T>
      org.planx.msd.util.NullDiscriminator<T>

All Implemented Interfaces:

Discriminator<T>

public class NullDiscriminator<T>
extends AbstractDiscriminator<T>

A Discriminator capable of discriminating a multiset of values into an equivalence class containing null elements and one or more equivalence classes containing the non-null elements as discriminated by another discriminator. The intention is to be able to extend discriminators that do not allow null input values to allow such values.

Author:

Thomas Ambus

Constructor Summary

NullDiscriminator(Discriminator<T> d)
Constructs a new NullDiscriminator wrapping the specified discriminator, thereby extending the wrapped discriminator to allow null values.

Method Summary

<U,S> Collection<List<S>>

discriminate(List<? extends U> values, Extractor<U,? extends T,S> e) Discriminates a List of values using an Extractor, and returns a Collection of Lists, each representing an equivalence class containing elements from values that are equivalent.

Methods inherited from class org.planx.msd.util.AbstractDiscriminator

discriminate

Methods inherited from class java.lang.Object

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

Constructor Detail

NullDiscriminator

public NullDiscriminator(Discriminator<T> d)

Constructs a new NullDiscriminator wrapping the specified discriminator, thereby extending the wrapped discriminator to allow null values.

Method Detail

discriminate

public <U,S> Collection<List<S>> discriminate(List<? extends U> values,
                                              Extractor<U,? extends T,S> e)

Description copied from interface: Discriminator

Discriminates a List of values using an Extractor, and returns a Collection of Lists, each representing an equivalence class containing elements from values that are equivalent. The Extractor performs the task of extracting two kinds of objects from the input values: The label which is the object equivalence is defined upon, and the value which is the object that will be returned. That is, the label determines which equivalence class the value goes into.

The Collection of Lists returned should be considered unmodifiable (though, in some cases they might actually be modifiable, but this behaviour should not be relied upon).

Specified by:

discriminate in interface Discriminator<T>

Specified by:

discriminate in class AbstractDiscriminator<T>