AbstractMultiValuedMap (Apache Commons Collections 4.4 API)

java.lang.Object
- org.apache.commons.collections4.multimap.AbstractMultiValuedMap<K,V>

Type Parameters:

K - the type of the keys in this map

V - the type of the values in this map

All Implemented Interfaces:

MultiValuedMap<K,V>

Direct Known Subclasses:

AbstractListValuedMap, AbstractSetValuedMap
```
public abstract class AbstractMultiValuedMap<K,V>
extends 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

Constructor Summary

Constructors
Modifier	Constructor and Description
`protected`	`AbstractMultiValuedMap()` Constructor needed for subclass serialisation.
`protected`	`AbstractMultiValuedMap(Map<K,? extends Collection<V>> map)` Constructor that wraps (not copies).

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`Map<K,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(Object key)` Returns `true` if this map contains a mapping for the specified key.
`boolean`	`containsMapping(Object key, Object value)` Checks whether the map contains a mapping for the specified key and value.
`boolean`	`containsValue(Object value)` Checks whether the map contains at least one mapping for the specified value.
`protected abstract Collection<V>`	`createCollection()`
`protected void`	`doReadObject(ObjectInputStream in)` Read the map in using a custom routine.
`protected void`	`doWriteObject(ObjectOutputStream out)` Write the map out using a custom routine.
`Collection<Map.Entry<K,V>>`	`entries()` Returns a `Collection` view of the mappings contained in this multi-valued map.
`boolean`	`equals(Object obj)`
`Collection<V>`	`get(K key)` Gets the collection of values associated with the specified key.
`protected Map<K,? extends Collection<V>>`	`getMap()` Gets the map being wrapped.
`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.
`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, Iterable<? extends V> values)` Adds Iterable values to the collection associated with the specified key.
`boolean`	`putAll(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.
`Collection<V>`	`remove(Object key)` Removes all values associated with the specified key.
`boolean`	`removeMapping(Object key, Object value)` Removes a specific key/value mapping from the multi-valued map.
`protected void`	`setMap(Map<K,? extends Collection<V>> map)` Sets the map being wrapped.
`int`	`size()` Gets the total size of the map.
`String`	`toString()`
`Collection<V>`	`values()` Gets a collection containing all the values in the map.

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

- Constructor Detail
  - AbstractMultiValuedMap
```
protected AbstractMultiValuedMap()
```
    Constructor needed for subclass serialisation.
  - AbstractMultiValuedMap
```
protected AbstractMultiValuedMap(Map<K,? extends Collection<V>> map)
```
    Constructor that wraps (not copies).
    
    Parameters:
    
    map - the map to wrap, must not be null
    
    Throws:
    
    NullPointerException - if the map is null
- Method Detail
  - getMap
```
protected Map<K,? extends Collection<V>> getMap()
```
    Gets the map being wrapped.
    
    Returns:
    
    the wrapped map
  - setMap
```
protected void setMap(Map<K,? extends Collection<V>> map)
```
    Sets the map being wrapped.
    NOTE: this method should only be used during deserialization
    
    Parameters:
    
    map - the map to wrap
  - createCollection
```
protected abstract Collection<V> createCollection()
```
  - containsKey
```
public boolean containsKey(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(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(Object key,
                               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 Collection<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 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 Collection<V> remove(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(Object key,
                             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 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 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(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:
    
    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:
    
    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 Map<K,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,
                      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:
    
    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(Object obj)
```
    Overrides:
    
    equals in class Object
  - hashCode
```
public int hashCode()
```
    Overrides:
    
    hashCode in class Object
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object
  - doWriteObject
```
protected void doWriteObject(ObjectOutputStream out)
                      throws IOException
```
    Write the map out using a custom routine.
    
    Parameters:
    
    out - the output stream
    
    Throws:
    
    IOException - any of the usual I/O related exceptions
  - doReadObject
```
protected void doReadObject(ObjectInputStream in)
                     throws IOException,
                            ClassNotFoundException
```
    Read the map in using a custom routine.
    
    Parameters:
    
    in - the input stream
    
    Throws:
    
    IOException - any of the usual I/O related exceptions
    
    ClassNotFoundException - if the stream contains an object which class can not be loaded
    
    ClassCastException - if the stream does not contain the correct objects

Class AbstractMultiValuedMap<K,V>

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

AbstractMultiValuedMap

AbstractMultiValuedMap

Method Detail

getMap

setMap

createCollection

containsKey

containsValue

containsMapping

entries

get

remove

removeMapping

isEmpty

keySet

size

values

clear

put

putAll

putAll

keys

asMap

putAll

mapIterator

equals

hashCode

toString

doWriteObject

doReadObject