IndexedCollection (Apache Commons Collections 4.0 API)

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

Version:

$Id: IndexedCollection.html 972421 2015-11-14 20:00:04Z tn $

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

Methods
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, equals, hashCode, isEmpty, iterator, setCollection, size, toArray, toArray, toString

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- 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>

Class IndexedCollection<K,C>

Constructor Summary

Method Summary

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

Methods inherited from class java.lang.Object

Constructor Detail

IndexedCollection

Method Detail

uniqueIndexedCollection

nonUniqueIndexedCollection

add

addAll

clear

contains

containsAll

get

values

reindex

remove

removeAll

retainAll