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## org.apache.commons.collections
Class MultiHashMap

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

All Implemented Interfaces:
  java.io.Serializable, java.lang.Cloneable, java.util.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 java.util.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: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (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 interface java.util.Map
`java.util.Map.Entry`

Constructor Summary
`MultiHashMap()` Deprecated. Constructor.
`MultiHashMap(int initialCapacity)` Deprecated. Constructor.
`MultiHashMap(int initialCapacity, float loadFactor)` Deprecated. Constructor.
`MultiHashMap(java.util.Map mapToCopy)` Deprecated. Constructor that copies the input map creating an independent copy.

Method Summary
`void` | `clear()` Deprecated. Clear the map.
`java.lang.Object` | `clone()` Deprecated. Clones the map creating an independent copy.
`boolean` | `containsValue(java.lang.Object value)` Deprecated. Checks whether the map contains the value specified.
`boolean` | `containsValue(java.lang.Object key, java.lang.Object value)` Deprecated. Checks whether the collection at the specified key contains the value.
`protected java.util.Collection` | `createCollection(java.util.Collection coll)` Deprecated. Creates a new instance of the map value Collection container.
`java.util.Collection` | `getCollection(java.lang.Object key)` Deprecated. Gets the collection mapped to the specified key.
`java.util.Iterator` | `iterator(java.lang.Object key)` Deprecated. Gets an iterator for the collection mapped to the specified key.
`java.lang.Object` | `put(java.lang.Object key, java.lang.Object value)` Deprecated. Adds the value to the collection associated with the specified key.
`void` | `putAll(java.util.Map map)` Deprecated. Override superclass to ensure that MultiMap instances are correctly handled.
`boolean` | `putAll(java.lang.Object key, java.util.Collection values)` Deprecated. Adds a collection of values to the collection associated with the specified key.
`java.lang.Object` | `remove(java.lang.Object key, java.lang.Object item)` Deprecated. Removes a specific value from map.
`int` | `size(java.lang.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.
`java.util.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(java.util.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 java.util.Collection getCollection(java.lang.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(java.lang.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 java.util.Iterator iterator(java.lang.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 java.lang.Object put(java.lang.Object key,
                                java.lang.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 `java.util.Map`
  Specified by:
    `put` in interface `MultiMap`
  Overrides:
    `put` in class `java.util.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(java.util.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 `java.util.Map`
  Overrides:
    `putAll` in class `java.util.HashMap`
  Parameters:
    `map` - the map to copy (either a normal or multi map)

### putAll

    public boolean putAll(java.lang.Object key,
                          java.util.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(java.lang.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 `java.util.Map`
  Specified by:
    `containsValue` in interface `MultiMap`
  Overrides:
    `containsValue` in class `java.util.HashMap`
  Parameters:
    `value` - the value to search for
  Returns:
    true if the map contains the value

### containsValue

    public boolean containsValue(java.lang.Object key,
                                 java.lang.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 java.lang.Object remove(java.lang.Object key,
                                   java.lang.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 `java.util.Map`
  Overrides:
    `clear` in class `java.util.HashMap`

### values

    public java.util.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 `java.util.Map`
  Specified by:
    `values` in interface `MultiMap`
  Overrides:
    `values` in class `java.util.HashMap`
  Returns:
    a collection view of the values contained in this map

### clone

    public java.lang.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 `java.util.HashMap`
  Returns:
    the cloned map

### createCollection

    protected java.util.Collection createCollection(java.util.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

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