MultiHashMap (Apache Commons Collections 3.2.2 API)

java.lang.Object
- java.util.AbstractMap
- - java.util.HashMap
  - - org.apache.commons.collections.MultiHashMap

All Implemented Interfaces:

Serializable, Cloneable, Map, MultiMap

Deprecated.
Class now available as MultiValueMap in map subpackage. This version is due to be removed in collections v4.0.
```
public class MultiHashMap
extends HashMap
implements MultiMap
```
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: 972404 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $

Author:

Christopher Berry, James Strachan, Steve Downey, Stephen Colebourne, Julien Buret, Serhiy Yevtushenko, Robert Ribnitz

See Also:
Serialized Form

Nested Class Summary
- Nested classes/interfaces inherited from class java.util.AbstractMap
  AbstractMap.SimpleEntry, AbstractMap.SimpleImmutableEntry
- Nested classes/interfaces inherited from interface java.util.Map
  Map.Entry

Constructor Summary

Constructors
Constructor and Description
`MultiHashMap()` Deprecated. Constructor.
`MultiHashMap(int initialCapacity)` Deprecated. Constructor.
`MultiHashMap(int initialCapacity, float loadFactor)` Deprecated. Constructor.
`MultiHashMap(Map mapToCopy)` Deprecated. Constructor that copies the input map creating an independent copy.

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`clear()` Deprecated. Clear the map.
`Object`	`clone()` Deprecated. Clones the map creating an independent copy.
`boolean`	`containsValue(Object value)` Deprecated. Checks whether the map contains the value specified.
`boolean`	`containsValue(Object key, Object value)` Deprecated. Checks whether the collection at the specified key contains the value.
`protected Collection`	`createCollection(Collection coll)` Deprecated. Creates a new instance of the map value Collection container.
`Collection`	`getCollection(Object key)` Deprecated. Gets the collection mapped to the specified key.
`Iterator`	`iterator(Object key)` Deprecated. Gets an iterator for the collection mapped to the specified key.
`Object`	`put(Object key, Object value)` Deprecated. Adds the value to the collection associated with the specified key.
`void`	`putAll(Map map)` Deprecated. Override superclass to ensure that MultiMap instances are correctly handled.
`boolean`	`putAll(Object key, Collection values)` Deprecated. Adds a collection of values to the collection associated with the specified key.
`Object`	`remove(Object key, Object item)` Deprecated. Removes a specific value from map.
`int`	`size(Object key)` Deprecated. Gets the size of the collection mapped to the specified key.
`int`	`totalSize()` Deprecated. Gets the total size of the map by counting all the values.
`Collection`	`values()` Deprecated. Gets a collection containing all the values in the map.

Methods inherited from class java.util.HashMap
containsKey, entrySet, get, isEmpty, keySet, remove, size

Methods inherited from class java.util.AbstractMap
equals, hashCode, toString

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

Methods inherited from interface org.apache.commons.collections.MultiMap
get, remove, size

Methods inherited from interface java.util.Map
containsKey, entrySet, equals, hashCode, isEmpty, keySet

- Constructor Detail
  - MultiHashMap
```
public MultiHashMap()
```
    Deprecated.
    
    Constructor.
  - MultiHashMap
```
public MultiHashMap(int initialCapacity)
```
    Deprecated.
    
    Constructor.
    
    Parameters:
    initialCapacity - the initial map capacity
  - MultiHashMap
```
public MultiHashMap(int initialCapacity,
            float loadFactor)
```
    Deprecated.
    
    Constructor.
    
    Parameters:
    initialCapacity - the initial map capacity
    loadFactor - the amount 0.0-1.0 at which to resize the map
  - MultiHashMap
```
public MultiHashMap(Map mapToCopy)
```
    Deprecated.
    
    Constructor that copies the input map creating an independent copy.
    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
- Method Detail
  - totalSize
```
public int totalSize()
```
    Deprecated.
    
    Gets the total size of the map by counting all the values.
    
    Returns:
    the total size of the map counting all values
    Since:
    
    Commons Collections 3.1
  - getCollection
```
public Collection getCollection(Object key)
```
    Deprecated.
    
    Gets the collection mapped to the specified key. This method is a convenience method to typecast the result of get(key).
    
    Parameters:
    key - the key to retrieve
    
    Returns:
    the collection mapped to the key, null if no mapping
    Since:
    
    Commons Collections 3.1
  - size
```
public int size(Object key)
```
    Deprecated.
    
    Gets the size of the collection mapped to the specified key.
    
    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
  - iterator
```
public Iterator iterator(Object key)
```
    Deprecated.
    
    Gets an iterator for the collection mapped to the specified key.
    
    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
  - put
```
public Object put(Object key,
         Object value)
```
    Deprecated.
    
    Adds the value to the collection associated with the specified key.
    Unlike a normal Map the previous value is not replaced. Instead the new value is added to the collection stored against the key.
    
    Specified by:
    
    put in interface Map
    
    Specified by:
    
    put in interface MultiMap
    
    Overrides:
    
    put in class HashMap
    
    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
  - putAll
```
public void putAll(Map map)
```
    Deprecated.
    
    Override superclass to ensure that MultiMap instances are correctly handled.
    NOTE: Prior to version 3.2, putAll(map) did not work properly when passed a MultiMap.
    
    Specified by:
    
    putAll in interface Map
    
    Overrides:
    
    putAll in class HashMap
    
    Parameters:
    map - the map to copy (either a normal or multi map)
  - putAll
```
public boolean putAll(Object key,
             Collection values)
```
    Deprecated.
    
    Adds a collection of values to the collection associated with the specified key.
    
    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
  - containsValue
```
public boolean containsValue(Object value)
```
    Deprecated.
    
    Checks whether the map contains the value specified.
    This checks all collections against all keys for the value, and thus could be slow.
    
    Specified by:
    
    containsValue in interface Map
    
    Specified by:
    
    containsValue in interface MultiMap
    
    Overrides:
    
    containsValue in class HashMap
    
    Parameters:
    value - the value to search for
    
    Returns:
    true if the map contains the value
  - containsValue
```
public boolean containsValue(Object key,
                    Object value)
```
    Deprecated.
    
    Checks whether the collection at the specified key contains the value.
    
    Parameters:
    value - the value to search for
    
    Returns:
    true if the map contains the value
    Since:
    
    Commons Collections 3.1
  - remove
```
public Object remove(Object key,
            Object item)
```
    Deprecated.
    
    Removes a specific value from map.
    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).
    
    Specified by:
    
    remove in interface MultiMap
    
    Parameters:
    key - the key to remove from
    item - the value to remove
    
    Returns:
    the value removed (which was passed in), null if nothing removed
  - clear
```
public void clear()
```
    Deprecated.
    
    Clear the map.
    This clears each collection in the map, and so may be slow.
    
    Specified by:
    
    clear in interface Map
    
    Overrides:
    
    clear in class HashMap
  - values
```
public Collection values()
```
    Deprecated.
    
    Gets a collection containing all the values in the map.
    This returns a collection containing the combination of values from all keys.
    
    Specified by:
    
    values in interface Map
    
    Specified by:
    
    values in interface MultiMap
    
    Overrides:
    
    values in class HashMap
    
    Returns:
    a collection view of the values contained in this map
  - clone
```
public Object clone()
```
    Deprecated.
    
    Clones the map creating an independent copy.
    The clone will shallow clone the collections as well as the map.
    
    Overrides:
    
    clone in class HashMap
    
    Returns:
    the cloned map
  - createCollection
```
protected Collection createCollection(Collection coll)
```
    Deprecated.
    
    Creates a new instance of the map value Collection container.
    This method can be overridden to use your own collection type.
    
    Parameters:
    coll - the collection to copy, may be null
    
    Returns:
    the new collection

Class MultiHashMap

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

Nested classes/interfaces inherited from interface java.util.Map

Constructor Summary

Method Summary

Methods inherited from class java.util.HashMap

Methods inherited from class java.util.AbstractMap

Methods inherited from class java.lang.Object

Methods inherited from interface org.apache.commons.collections.MultiMap

Methods inherited from interface java.util.Map

Constructor Detail

MultiHashMap

MultiHashMap

MultiHashMap

MultiHashMap

Method Detail

totalSize

getCollection

size

iterator

put

putAll

putAll

containsValue

containsValue

remove

clear

values

clone

createCollection