org.apache.commons.collections.map
public class MultiValueMap extends AbstractMapDecorator implements MultiMap
A MultiMap
is a Map with slightly different semantics.
Putting a value into the map will add the value to a Collection at that key.
Getting a value will return a Collection, holding all the values put to that key.
This implementation is a decorator, allowing any Map implementation to be used as the base.
In addition, this implementation allows the type of collection used
for the values to be controlled. By default, an ArrayList
is used, however a Class
to instantiate may be specified,
or a factory that returns a Collection
instance.
Note that MultiValueMap is not synchronized and is not thread-safe. If you wish to use this map from multiple threads concurrently, you must use appropriate synchronization. This class may throw exceptions when accessed by concurrent threads without synchronization.
Since: Commons Collections 3.2
Version: $Revision: 348007 $ $Date: 2005-11-21 22:52:57 +0000 (Mon, 21 Nov 2005) $
Constructor Summary | |
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MultiValueMap()
Creates a MultiValueMap based on a HashMap and
storing the multiple values in an ArrayList . | |
protected | MultiValueMap(Map map, Factory collectionFactory)
Creates a MultiValueMap which decorates the given map and
creates the value collections using the supplied collectionFactory .
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Method Summary | |
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void | clear()
Clear the map. |
boolean | containsValue(Object value)
Checks whether the map contains the value specified.
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boolean | containsValue(Object key, Object value)
Checks whether the collection at the specified key contains the value.
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protected Collection | createCollection(int size)
Creates a new instance of the map value Collection container
using the factory.
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static MultiValueMap | decorate(Map map)
Creates a map which wraps the given map and
maps keys to ArrayLists.
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static MultiValueMap | decorate(Map map, Class collectionClass)
Creates a map which decorates the given map and
maps keys to collections of type collectionClass .
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static MultiValueMap | decorate(Map map, Factory collectionFactory)
Creates a map which decorates the given map and
creates the value collections using the supplied collectionFactory .
|
Collection | getCollection(Object key)
Gets the collection mapped to the specified key.
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Iterator | iterator(Object key)
Gets an iterator for the collection mapped to the specified key.
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Object | put(Object key, Object value)
Adds the value to the collection associated with the specified key.
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void | putAll(Map map)
Override superclass to ensure that MultiMap instances are
correctly handled.
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boolean | putAll(Object key, Collection values)
Adds a collection of values to the collection associated with
the specified key.
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Object | remove(Object key, Object value)
Removes a specific value from map.
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int | size(Object key)
Gets the size of the collection mapped to the specified key.
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int | totalSize()
Gets the total size of the map by counting all the values.
|
Collection | values()
Gets a collection containing all the values in the map.
|
HashMap
and
storing the multiple values in an ArrayList
.map
and
creates the value collections using the supplied collectionFactory
.
Parameters: map the map to decorate collectionFactory the collection factory which must return a Collection instance
This checks all collections against all keys for the value, and thus could be slow.
Parameters: value the value to search for
Returns: true if the map contains the value
Parameters: value the value to search for
Returns: true if the map contains the value
This method can be overridden to perform your own processing instead of using the factory.
Parameters: size the collection size that is about to be added
Returns: the new collection
Parameters: map the map to wrap
map
and
maps keys to collections of type collectionClass
.
Parameters: map the map to wrap collectionClass the type of the collection class
map
and
creates the value collections using the supplied collectionFactory
.
Parameters: map the map to decorate collectionFactory the collection factory (must return a Collection object).
get(key)
.
Parameters: key the key to retrieve
Returns: the collection mapped to the key, null if no mapping
Parameters: key the key to get an iterator for
Returns: the iterator of the collection at the key, empty iterator if key not in map
Unlike a normal Map
the previous value is not replaced.
Instead the new value is added to the collection stored against the key.
Parameters: key the key to store against value the value to add to the collection at the key
Returns: the value added if the map changed and null if the map did not change
If you call this method with a normal map, each entry is
added using put(Object,Object)
.
If you call this method with a multi map, each entry is
added using putAll(Object,Collection)
.
Parameters: map the map to copy (either a normal or multi map)
Parameters: key the key to store against values the values to add to the collection at the key, null ignored
Returns: true if this map changed
The item is removed from the collection mapped to the specified key. Other values attached to that key are unaffected.
If the last value for a key is removed, null
will be returned
from a subsequant get(key)
.
Parameters: key the key to remove from value the value to remove
Returns: the value removed (which was passed in), null if nothing removed
Parameters: key the key to get size for
Returns: the size of the collection at the key, zero if key not in map
Returns: the total size of the map counting all values
This returns a collection containing the combination of values from all keys.
Returns: a collection view of the values contained in this map