jaggregate
Class Collections

java.lang.Object
  jaggregate.Collections

public class Collections
extends Object

Methods that should be on Collection, but aren't for reasons of type safety or generics restrictions.

Version:

$Id: Collections.java,v 1.9 2008/10/03 19:01:23 pholser Exp $

Author:

Paul Holser

Method Summary

static <T,E extends T> T[]	toArray(Collection<E> collection, Class<T> componentType) Answers an array with the same elements as the given collection, with the same size as the collection, and a component type of the given class.
static <E,V> Dictionary<E,V>	toDictionary(Collection<E> elements, UnaryFunctor<? super E,? extends V> mapper) Answers a dictionary whose keys are the elements of the given collection and whose values are the results of applying the given mapper to the associated element from the collection.
static <E,V> IdentityDictionary<E,V>	toIdentityDictionary(Collection<E> elements, UnaryFunctor<? super E,? extends V> mapper) Answers a dictionary whose keys are the elements of the given collection and whose values are the results of applying the given mapper to the associated element from the collection.

Methods inherited from class java.lang.Object

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

Method Detail

toArray

public static <T,E extends T> T[] toArray(Collection<E> collection,
                                          Class<T> componentType)

Answers an array with the same elements as the given collection, with the same size as the collection, and a component type of the given class.

If collection maintains an ordering for its elements, the order of those elements will be preserved in the result.

Type Parameters:

T - the component type of the array to be created

E - the type of the elements in the collection to convert

Parameters:

collection - the collection to make an array from

componentType - the desired type of the result array's components

Returns:

an array of collection's elements

Throws:

NullPointerException - if either collection or componentType is null

IllegalArgumentException - if componentType is Void.TYPE

See Also:

Collection.toArray(), Creating an array from a generic Java collection

toDictionary

public static <E,V> Dictionary<E,V> toDictionary(Collection<E> elements,
                                                 UnaryFunctor<? super E,? extends V> mapper)

Answers a dictionary whose keys are the elements of the given collection and whose values are the results of applying the given mapper to the associated element from the collection.

elements are traversed in the order specified by Collection.forEachDo(UnaryFunctor).

This method would be on Collection if it weren't for these bugs.

Type Parameters:

E - the type of elements in the given collection

V - the types of the values in the resultant dictionary

Parameters:

elements - a collection

mapper - a function to apply to each element of elements

Returns:

a mapping from elements to mapped values

Throws:

NullPointerException - if either elements or mapper is null

toIdentityDictionary

public static <E,V> IdentityDictionary<E,V> toIdentityDictionary(Collection<E> elements,
                                                                 UnaryFunctor<? super E,? extends V> mapper)

Answers a dictionary whose keys are the elements of the given collection and whose values are the results of applying the given mapper to the associated element from the collection.

elements are traversed in the order specified by Collection.forEachDo(UnaryFunctor).

This method would be on Collection if it weren't for these bugs.

Type Parameters:

E - the type of elements in the given collection

V - the types of the values in the resultant dictionary

Parameters:

elements - a collection

mapper - a function to apply to each element of elements

Returns:

a mapping from elements to mapped values

Throws:

NullPointerException - if either elements or mapper is null