org.apache.commons.collections
public class MultiHashMap extends HashMap implements MultiMap
Deprecated: Class now available as MultiValueMap in map subpackage. This version is due to be removed in collections v4.0.
MultiHashMap
is the default implementation of the
MultiMap
interface.
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 uses an ArrayList
as the collection.
The internal storage list is made available without cloning via the
get(Object)
and entrySet()
methods.
The implementation returns null
when there are no values mapped to a key.
For example:
MultiMap mhm = new MultiHashMap(); mhm.put(key, "A"); mhm.put(key, "B"); mhm.put(key, "C"); List list = (List) mhm.get(key);
list
will be a list containing "A", "B", "C".
Since: Commons Collections 2.0
Version: $Revision: 372373 $ $Date: 2006-01-26 00:10:43 +0000 (Thu, 26 Jan 2006) $
Constructor Summary | |
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MultiHashMap()
Constructor. | |
MultiHashMap(int initialCapacity)
Constructor.
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MultiHashMap(int initialCapacity, float loadFactor)
Constructor.
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MultiHashMap(Map mapToCopy)
Constructor that copies the input map creating an independent copy.
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Method Summary | |
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void | clear()
Clear the map.
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Object | clone()
Clones the map creating an independent copy.
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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(Collection coll)
Creates a new instance of the map value Collection container.
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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 item)
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.
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Collection | values()
Gets a collection containing all the values in the map.
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Parameters: initialCapacity the initial map capacity
Parameters: initialCapacity the initial map capacity loadFactor the amount 0.0-1.0 at which to resize the map
This method performs different behaviour depending on whether the map specified is a MultiMap or not. If a MultiMap is specified, each internal collection is also cloned. If the specified map only implements Map, then the values are not cloned.
NOTE: From Commons Collections 3.1 this method correctly copies a MultiMap to form a truly independent new map. NOTE: From Commons Collections 3.2 this method delegates to the newly added putAll(Map) override method.
Parameters: mapToCopy a Map to copy
This clears each collection in the map, and so may be slow.
The clone will shallow clone the collections as well as the map.
Returns: the cloned map
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
Since: Commons Collections 3.1
This method can be overridden to use your own collection type.
Parameters: coll the collection to copy, may be null
Returns: the new collection
get(key)
.
Parameters: key the key to retrieve
Returns: the collection mapped to the key, null if no mapping
Since: Commons Collections 3.1
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
Since: Commons Collections 3.1
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
NOTE: Prior to version 3.2, putAll(map) did not work properly when passed a MultiMap.
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
Since: Commons Collections 3.1
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 item 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
Since: Commons Collections 3.1
Returns: the total size of the map counting all values
Since: Commons Collections 3.1
This returns a collection containing the combination of values from all keys.
Returns: a collection view of the values contained in this map