org.apache.commons.collections4.collection

Class IndexedCollection<K,C>

java.lang.Object

org.apache.commons.collections4.collection.AbstractCollectionDecorator<C>

org.apache.commons.collections4.collection.IndexedCollection<K,C>

Type Parameters:

K - the type of object in the index.

C - the type of object in the collection.

All Implemented Interfaces:

Serializable, Iterable<C>, Collection<C>

public class IndexedCollection<K,C>
extends AbstractCollectionDecorator<C>

An IndexedCollection is a Map-like view onto a Collection. It accepts a keyTransformer to define how the keys are converted from the values.

Modifications made to this decorator modify the index as well as the decorated Collection. However, modifications to the underlying Collection will not update the index and it will get out of sync.

If modification of the decorated Collection is unavoidable, then a call to reindex() will update the index to the current contents of the Collection.

Since:

4.0

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
IndexedCollection(Collection<C> coll, Transformer<C,K> keyTransformer, MultiMap<K,C> map, boolean uniqueIndex) Create a IndexedCollection.

Method Summary

Modifier and Type	Method and Description
boolean	add(C object)
boolean	addAll(Collection<? extends C> coll)
void	clear()
boolean	contains(Object object)
boolean	containsAll(Collection<?> coll)
C	get(K key) Get the element associated with the given key.
static <K,C> IndexedCollection<K,C>	nonUniqueIndexedCollection(Collection<C> coll, Transformer<C,K> keyTransformer) Create an IndexedCollection for a non-unique index.
void	reindex() Clears the index and re-indexes the entire decorated Collection.
boolean	remove(Object object)
boolean	removeAll(Collection<?> coll)
boolean	retainAll(Collection<?> coll)
static <K,C> IndexedCollection<K,C>	uniqueIndexedCollection(Collection<C> coll, Transformer<C,K> keyTransformer) Create an IndexedCollection for a unique index.
Collection<C>	values(K key) Get all elements associated with the given key.

Methods inherited from class org.apache.commons.collections4.collection.AbstractCollectionDecorator

decorated, isEmpty, iterator, setCollection, size, toArray, toArray, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Collection

equals, hashCode, parallelStream, removeIf, spliterator, stream

Methods inherited from interface java.lang.Iterable

forEach

Constructor Detail

IndexedCollection

public IndexedCollection(Collection<C> coll,
                         Transformer<C,K> keyTransformer,
                         MultiMap<K,C> map,
                         boolean uniqueIndex)

Create a IndexedCollection.

Parameters:

coll - decorated Collection

keyTransformer - Transformer for generating index keys

map - map to use as index

uniqueIndex - if the index shall enforce uniqueness of index keys

Method Detail

uniqueIndexedCollection

public static <K,C> IndexedCollection<K,C> uniqueIndexedCollection(Collection<C> coll,
                                                                   Transformer<C,K> keyTransformer)

Create an IndexedCollection for a unique index.

If an element is added, which maps to an existing key, an IllegalArgumentException will be thrown.

Type Parameters:

K - the index object type.

C - the collection type.

Parameters:

coll - the decorated Collection.

keyTransformer - the Transformer for generating index keys.

Returns:

the created IndexedCollection.

nonUniqueIndexedCollection

public static <K,C> IndexedCollection<K,C> nonUniqueIndexedCollection(Collection<C> coll,
                                                                      Transformer<C,K> keyTransformer)

Create an IndexedCollection for a non-unique index.

Type Parameters:

K - the index object type.

C - the collection type.

Parameters:

coll - the decorated Collection.

keyTransformer - the Transformer for generating index keys.

Returns:

the created IndexedCollection.

add

public boolean add(C object)

Specified by:

add in interface Collection<C>

Overrides:

add in class AbstractCollectionDecorator<C>

Throws:

IllegalArgumentException - if the object maps to an existing key and the index enforces a uniqueness constraint

addAll

public boolean addAll(Collection<? extends C> coll)

Specified by:

addAll in interface Collection<C>

Overrides:

addAll in class AbstractCollectionDecorator<C>

clear

public void clear()

Specified by:

clear in interface Collection<C>

Overrides:

clear in class AbstractCollectionDecorator<C>

contains

public boolean contains(Object object)

Note: uses the index for fast lookup

Specified by:

contains in interface Collection<C>

Overrides:

contains in class AbstractCollectionDecorator<C>

containsAll

public boolean containsAll(Collection<?> coll)

Note: uses the index for fast lookup

Specified by:

containsAll in interface Collection<C>

Overrides:

containsAll in class AbstractCollectionDecorator<C>

get

public C get(K key)

Get the element associated with the given key.

In case of a non-unique index, this method will return the first value associated with the given key. To retrieve all elements associated with a key, use values(Object).

Parameters:

key - key to look up

Returns:

element found

See Also:

values(Object)

values

public Collection<C> values(K key)

Get all elements associated with the given key.

Parameters:

key - key to look up

Returns:

a collection of elements found, or null if contains(key) == false

reindex

public void reindex()

Clears the index and re-indexes the entire decorated Collection.

remove

public boolean remove(Object object)

Specified by:

remove in interface Collection<C>

Overrides:

remove in class AbstractCollectionDecorator<C>

removeAll

public boolean removeAll(Collection<?> coll)

Specified by:

removeAll in interface Collection<C>

Overrides:

removeAll in class AbstractCollectionDecorator<C>

retainAll

public boolean retainAll(Collection<?> coll)

Specified by:

retainAll in interface Collection<C>

Overrides:

retainAll in class AbstractCollectionDecorator<C>