org.apache.commons.collections4.multimap

Class AbstractMultiValuedMap<K,V>

java.lang.Object

org.apache.commons.collections4.multimap.AbstractMultiValuedMap<K,V>

All Implemented Interfaces:

MultiValuedMap<K,V>

Direct Known Subclasses:

AbstractListValuedMap, AbstractSetValuedMap

public abstract class AbstractMultiValuedMap<K,V>
extends java.lang.Object
implements MultiValuedMap<K,V>

Abstract implementation of the MultiValuedMap interface to simplify the creation of subclass implementations.

Subclasses specify a Map implementation to use as the internal storage.

Since:

4.1

Method Summary

Modifier and Type	Method and Description
java.util.Map<K,java.util.Collection<V>>	asMap() Returns a view of this multi-valued map as a Map from each distinct key to the non-empty collection of that key's associated values.
void	clear() Removes all of the mappings from this map (optional operation).
boolean	containsKey(java.lang.Object key) Returns true if this map contains a mapping for the specified key.
boolean	containsMapping(java.lang.Object key, java.lang.Object value) Checks whether the map contains a mapping for the specified key and value.
boolean	containsValue(java.lang.Object value) Checks whether the map contains at least one mapping for the specified value.
java.util.Collection<java.util.Map.Entry<K,V>>	entries() Returns a Collection view of the mappings contained in this multi-valued map.
boolean	equals(java.lang.Object obj)
java.util.Collection<V>	get(K key) Gets the collection of values associated with the specified key.
int	hashCode()
boolean	isEmpty() Returns true if this map contains no key-value mappings.
MultiSet<K>	keys() Returns a MultiSet view of the key mapping contained in this map.
java.util.Set<K>	keySet() Returns a Set view of the keys contained in this multi-valued map.
MapIterator<K,V>	mapIterator() Obtains a MapIterator over this multi-valued map.
boolean	put(K key, V value) Adds the value to the collection associated with the specified key.
boolean	putAll(K key, java.lang.Iterable<? extends V> values) Adds Iterable values to the collection associated with the specified key.
boolean	putAll(java.util.Map<? extends K,? extends V> map) Copies all of the mappings from the specified map to this map.
boolean	putAll(MultiValuedMap<? extends K,? extends V> map) Copies all of the mappings from the specified MultiValuedMap to this map.
java.util.Collection<V>	remove(java.lang.Object key) Removes all values associated with the specified key.
boolean	removeMapping(java.lang.Object key, java.lang.Object value) Removes a specific key/value mapping from the multi-valued map.
int	size() Gets the total size of the map.
java.lang.String	toString()
java.util.Collection<V>	values() Gets a collection containing all the values in the map.

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Method Detail

containsKey

public boolean containsKey(java.lang.Object key)

Description copied from interface: MultiValuedMap

Returns true if this map contains a mapping for the specified key. More formally, returns true if and only if this map contains a mapping for a key k such that (key==null ? k==null : key.equals(k)). (There can be at most one such mapping.)

Specified by:

containsKey in interface MultiValuedMap<K,V>

Parameters:

key - key whose presence in this map is to be tested

Returns:

true if this map contains a mapping for the specified key

containsValue

public boolean containsValue(java.lang.Object value)

Description copied from interface: MultiValuedMap

Checks whether the map contains at least one mapping for the specified value.

Specified by:

containsValue in interface MultiValuedMap<K,V>

Parameters:

value - the value to search for

Returns:

true if the map contains the value

containsMapping

public boolean containsMapping(java.lang.Object key,
                               java.lang.Object value)

Description copied from interface: MultiValuedMap

Checks whether the map contains a mapping for the specified key and value.

Specified by:

containsMapping in interface MultiValuedMap<K,V>

Parameters:

key - the key to search for

value - the value to search for

Returns:

true if the map contains the value

entries

public java.util.Collection<java.util.Map.Entry<K,V>> entries()

Description copied from interface: MultiValuedMap

Returns a Collection view of the mappings contained in this multi-valued map.

The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa.

Specified by:

entries in interface MultiValuedMap<K,V>

Returns:

a set view of the mappings contained in this map

get

public java.util.Collection<V> get(K key)

Gets the collection of values associated with the specified key. This would return an empty collection in case the mapping is not present

Specified by:

get in interface MultiValuedMap<K,V>

Parameters:

key - the key to retrieve

Returns:

the Collection of values, will return an empty Collection for no mapping

remove

public java.util.Collection<V> remove(java.lang.Object key)

Removes all values associated with the specified key.

A subsequent get(Object) would return an empty collection.

Specified by:

remove in interface MultiValuedMap<K,V>

Parameters:

key - the key to remove values from

Returns:

the Collection of values removed, will return an empty, unmodifiable collection for no mapping found

removeMapping

public boolean removeMapping(java.lang.Object key,
                             java.lang.Object value)

Removes a specific key/value mapping from the multi-valued map.

The value 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, an empty collection would be returned from a subsequent get(Object).

Specified by:

removeMapping in interface MultiValuedMap<K,V>

Parameters:

key - the key to remove from

value - the value to remove

Returns:

true if the mapping was removed, false otherwise

isEmpty

public boolean isEmpty()

Description copied from interface: MultiValuedMap

Returns true if this map contains no key-value mappings.

Specified by:

isEmpty in interface MultiValuedMap<K,V>

Returns:

true if this map contains no key-value mappings

keySet

public java.util.Set<K> keySet()

Description copied from interface: MultiValuedMap

Returns a Set view of the keys contained in this multi-valued map.

The set is backed by the map, so changes to the map are reflected in the set, and vice-versa.

If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation), the result of the iteration is undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Specified by:

keySet in interface MultiValuedMap<K,V>

Returns:

a set view of the keys contained in this map

size

public int size()

Gets the total size of the map.

Implementations would return the total size of the map which is the count of the values from all keys.

This implementation does not cache the total size of the multi-valued map, but rather calculates it by iterating over the entries of the underlying map.

Specified by:

size in interface MultiValuedMap<K,V>

Returns:

the total size of the map

values

public java.util.Collection<V> values()

Gets a collection containing all the values in the map.

Returns a collection containing all the values from all keys.

Specified by:

values in interface MultiValuedMap<K,V>

Returns:

a collection view of the values contained in this map

clear

public void clear()

Description copied from interface: MultiValuedMap

Removes all of the mappings from this map (optional operation).

The map will be empty after this call returns.

Specified by:

clear in interface MultiValuedMap<K,V>

put

public boolean put(K key,
                   V value)

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 MultiValuedMap<K,V>

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 boolean putAll(java.util.Map<? extends K,? extends V> map)

Copies all of the mappings from the specified map to this map. The effect of this call is equivalent to that of calling put(k, v) on this map once for each mapping from key k to value v in the specified map. The behavior of this operation is undefined if the specified map is modified while the operation is in progress.

Specified by:

putAll in interface MultiValuedMap<K,V>

Parameters:

map - mappings to be stored in this map, may not be null

Returns:

true if the map changed as a result of this operation

Throws:

java.lang.NullPointerException - if map is null

putAll

public boolean putAll(MultiValuedMap<? extends K,? extends V> map)

Copies all of the mappings from the specified MultiValuedMap to this map. The effect of this call is equivalent to that of calling put(k, v) on this map once for each mapping from key k to value v in the specified map. The behavior of this operation is undefined if the specified map is modified while the operation is in progress.

Specified by:

putAll in interface MultiValuedMap<K,V>

Parameters:

map - mappings to be stored in this map, may not be null

Returns:

true if the map changed as a result of this operation

Throws:

java.lang.NullPointerException - if map is null

keys

public MultiSet<K> keys()

Returns a MultiSet view of the key mapping contained in this map.

Returns a MultiSet of keys with its values count as the count of the MultiSet. This multiset is backed by the map, so any changes in the map is reflected here. Any method which modifies this multiset like add, remove, Iterator.remove() etc throws UnsupportedOperationException.

Specified by:

keys in interface MultiValuedMap<K,V>

Returns:

a bag view of the key mapping contained in this map

asMap

public java.util.Map<K,java.util.Collection<V>> asMap()

Description copied from interface: MultiValuedMap

Returns a view of this multi-valued map as a Map from each distinct key to the non-empty collection of that key's associated values.

Note that this.asMap().get(k) is equivalent to this.get(k) only when k is a key contained in the multi-valued map; otherwise it returns null as opposed to an empty collection.

Changes to the returned map or the collections that serve as its values will update the underlying multi-valued map, and vice versa. The map does not support put or putAll, nor do its entries support setValue.

Specified by:

asMap in interface MultiValuedMap<K,V>

Returns:

a map view of the mappings in this multi-valued map

putAll

public boolean putAll(K key,
                      java.lang.Iterable<? extends V> values)

Adds Iterable values to the collection associated with the specified key.

Specified by:

putAll in interface MultiValuedMap<K,V>

Parameters:

key - the key to store against

values - the values to add to the collection at the key, may not be null

Returns:

true if this map changed

Throws:

java.lang.NullPointerException - if values is null

mapIterator

public MapIterator<K,V> mapIterator()

Description copied from interface: MultiValuedMap

Obtains a MapIterator over this multi-valued map.

A map iterator is an efficient way of iterating over maps. There is no need to access the entries collection or use Map.Entry objects.

Specified by:

mapIterator in interface MultiValuedMap<K,V>

Returns:

a map iterator

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object