Package org.apache.commons.collections

Class MultiHashMap

java.lang.Object
java.util.AbstractMap<K,V>
java.util.HashMap
org.apache.commons.collections.MultiHashMap
All Implemented Interfaces:
Serializable, Cloneable, Map, MultiMap
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: 646777 $ $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:

  • Constructor Details

    • 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 Details

    • 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

    • removeMapping

      public Object removeMapping(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:
      removeMapping 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