Apache Commons Collections 4.4 · org.apache.commons.collections4.MultiValuedMap

Method Summary

Modifier and Type	Method and Description
public Map<K, Collection<V>>	Returns: a map view of the mappings in this multi-valued map 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.
public void	clear() Removes all of the mappings from this map (optional operation).
public boolean	Returns: true if this map contains a mapping for the specified key containsKey(Object key whose presence in this map is to be tested key) Returns `true` if this map contains a mapping for the specified key.
public boolean	Returns: true if the map contains the value containsMapping(Object the key to search for key, Object the value to search for value) Checks whether the map contains a mapping for the specified key and value.
public boolean	Returns: true if the map contains the value containsValue(Object the value to search for value) Checks whether the map contains at least one mapping for the specified value.
public Collection<Map.Entry<K, V>>	Returns: a set view of the mappings contained in this map entries() Returns a `Collection` view of the mappings contained in this multi-valued map.
public Collection<V>	Returns: the `Collection` of values, implementations should return an empty collection for no mapping get(K the key to retrieve key) Returns a view collection of the values associated with the specified key.
public boolean	Returns: `true` if this map contains no key-value mappings isEmpty() Returns `true` if this map contains no key-value mappings.
public MultiSet<K>	Returns: a multiset view of the keys contained in this map keys() Returns a `MultiSet` view of the keys contained in this multi-valued map.
public Set<K>	Returns: a set view of the keys contained in this map keySet() Returns a `Set` view of the keys contained in this multi-valued map.
public MapIterator<K, V>	Returns: a map iterator mapIterator() Obtains a `MapIterator` over this multi-valued map.
public boolean	Returns: true if the map changed as a result of this put operation, or false if the map already contained the key-value mapping and the collection type does not allow duplicate values, e.g. when using a Set put(K the key to store against key, V the value to add to the collection at the key value) Adds a key-value mapping to this multi-valued map.
public boolean	Returns: true if the map changed as a result of this operation putAll(K the key to store against key, Iterable<? extends V> the values to add to the collection at the key, may not be null values) Adds a mapping to the specified key for all values contained in the given Iterable.
public boolean	Returns: true if the map changed as a result of this operation putAll(Map<? extends K, ? extends V> mappings to be stored in this map, may not be null map) Copies all mappings from the specified map to this multi-valued map (optional operation).
public boolean	Returns: true if the map changed as a result of this operation putAll(MultiValuedMap<? extends K, ? extends V> mappings to be stored in this map, may not be null map) Copies all mappings from the specified map to this multi-valued map (optional operation).
public Collection<V>	Returns: the values that were removed remove(Object the key to remove values from key) Removes all values associated with the specified key.
public boolean	Returns: true if the mapping was removed, false otherwise removeMapping(Object the key to remove from key, Object the item to remove item) Removes a key-value mapping from the map.
public int	Returns: the total size of the map size() Gets the total size of the map.
public Collection<V>	Returns: a collection view of the values contained in this multi-valued map values() Gets a `Collection` view of all values contained in this multi-valued map.

Method Detail

asMap back to summary

asMap	back to summary
public 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. 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`. Returns:Map<K, Collection<V>> a map view of the mappings in this multi-valued map

public 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.

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.

Returns:Map<K, Collection<V>>: a map view of the mappings in this multi-valued map

clear	back to summary
public void clear() Removes all of the mappings from this map (optional operation). The map will be empty after this call returns. Exceptions UnsupportedOperationException: if the map is unmodifiable

clear

back to summary

public void clear()

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

The map will be empty after this call returns.

Exceptions

UnsupportedOperationException:: if the map is unmodifiable

containsKey back to summary

containsKey	back to summary
public boolean containsKey(Object key) 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.) Parameters key:Object key whose presence in this map is to be tested Returns:boolean true if this map contains a mapping for the specified key Exceptions NullPointerException: if the specified key is null and this map does not permit null keys (optional)

public boolean containsKey(Object key)

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.)

Parameters

key:Object: key whose presence in this map is to be tested

Returns:boolean

true if this map contains a mapping for the specified key

Exceptions

NullPointerException:: if the specified key is null and this map does not permit null keys (optional)

containsMapping	back to summary
public boolean containsMapping(Object key, Object value) Checks whether the map contains a mapping for the specified key and value. Parameters key:Object the key to search for value:Object the value to search for Returns:boolean true if the map contains the value

containsMapping

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public boolean containsMapping(Object key, Object value)

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

Parameters

key:Object: the key to search for
value:Object: the value to search for

Returns:boolean

true if the map contains the value

containsValue	back to summary
public boolean containsValue(Object value) Checks whether the map contains at least one mapping for the specified value. Parameters value:Object the value to search for Returns:boolean true if the map contains the value Exceptions NullPointerException: if the value is null and null values are not supported by the used collection types (optional)

containsValue

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public boolean containsValue(Object value)

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

Parameters

value:Object: the value to search for

Returns:boolean

true if the map contains the value

Exceptions

NullPointerException:: if the value is null and null values are not supported by the used collection types (optional)

entries back to summary

entries	back to summary
public Collection<Map.Entry<K, V>> entries() 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. Returns:Collection<Map.Entry<K, V>> a set view of the mappings contained in this map

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

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.

Returns:Collection<Map.Entry<K, V>>: a set view of the mappings contained in this map

get back to summary

get	back to summary
public Collection<V> get(K key) Returns a view collection of the values associated with the specified key. This method will return an empty collection if `containsKey(Object)` returns `false`. Changes to the returned collection will update the underlying `MultiValuedMap` and vice-versa. Parameters key:K the key to retrieve Returns:Collection<V> the `Collection` of values, implementations should return an empty collection for no mapping Exceptions NullPointerException: if the key is null and null keys are invalid (optional)

public Collection<V> get(K key)

Returns a view collection of the values associated with the specified key.

This method will return an empty collection if containsKey(Object) returns false. Changes to the returned collection will update the underlying MultiValuedMap and vice-versa.

Parameters

key:K: the key to retrieve

Returns:Collection<V>

the Collection of values, implementations should return an empty collection for no mapping

Exceptions

NullPointerException:: if the key is null and null keys are invalid (optional)

isEmpty back to summary

isEmpty	back to summary
public boolean isEmpty() Returns `true` if this map contains no key-value mappings. Returns:boolean `true` if this map contains no key-value mappings

public boolean isEmpty()

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

Returns:boolean: true if this map contains no key-value mappings

keys back to summary

keys	back to summary
public MultiSet<K> keys() Returns a `MultiSet` view of the keys contained in this multi-valued map. The `MultiSet#getCount(Object)` method of the returned multiset will give the same result a calling `get(Object).size()` for the same key. This multiset is backed by the map, so any changes in the map are reflected in the multiset. Returns:MultiSet<K> a multiset view of the keys contained in this map

public MultiSet<K> keys()

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

The MultiSet#getCount(Object) method of the returned multiset will give the same result a calling get(Object).size() for the same key.

This multiset is backed by the map, so any changes in the map are reflected in the multiset.

Returns:MultiSet<K>: a multiset view of the keys contained in this map

keySet back to summary

keySet	back to summary
public Set<K> keySet() 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. Returns:Set<K> a set view of the keys contained in this map

public Set<K> keySet()

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.

Returns:Set<K>: a set view of the keys contained in this map

mapIterator back to summary

mapIterator	back to summary
public MapIterator<K, V> mapIterator() 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. Returns:MapIterator<K, V> a map iterator

public MapIterator<K, V> mapIterator()

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.

Returns:MapIterator<K, V>: a map iterator

put back to summary

put	back to summary
public boolean put(K key, V value) Adds a key-value mapping to this multi-valued map. Unlike a normal `Map` the previous value is not replaced. Instead the new value is added to the collection stored against the key. Depending on the collection type used, duplicate key-value mappings may be allowed. The method will return `true` if the size of the multi-valued map has been increased because of this operation. Parameters key:K the key to store against value:V the value to add to the collection at the key Returns:boolean true if the map changed as a result of this put operation, or false if the map already contained the key-value mapping and the collection type does not allow duplicate values, e.g. when using a Set Exceptions UnsupportedOperationException: if the put operation is not supported by this multi-valued map, e.g. if it is unmodifiable NullPointerException: if the key or value is null and null is invalid (optional) IllegalArgumentException: if some aspect of the specified key or value prevents it from being stored in this multi-valued map

public boolean put(K key, V value)

Adds a key-value mapping to this multi-valued map.

Unlike a normal Map the previous value is not replaced. Instead the new value is added to the collection stored against the key. Depending on the collection type used, duplicate key-value mappings may be allowed.

The method will return true if the size of the multi-valued map has been increased because of this operation.

Parameters

key:K: the key to store against
value:V: the value to add to the collection at the key

Returns:boolean

true if the map changed as a result of this put operation, or false if the map already contained the key-value mapping and the collection type does not allow duplicate values, e.g. when using a Set

Exceptions

UnsupportedOperationException:: if the put operation is not supported by this multi-valued map, e.g. if it is unmodifiable
NullPointerException:: if the key or value is null and null is invalid (optional)
IllegalArgumentException:: if some aspect of the specified key or value prevents it from being stored in this multi-valued map

putAll	back to summary
public boolean putAll(K key, Iterable<? extends V> values) Adds a mapping to the specified key for all values contained in the given Iterable. Parameters key:K the key to store against values:Iterable<? extends V> the values to add to the collection at the key, may not be null Returns:boolean true if the map changed as a result of this operation Exceptions NullPointerException: if the specified iterable is null, or if this map does not permit null keys or values, and the specified key or values contain null (optional)

putAll

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

Adds a mapping to the specified key for all values contained in the given Iterable.

Parameters

key:K: the key to store against
values:Iterable<? extends V>: the values to add to the collection at the key, may not be null

Returns:boolean

true if the map changed as a result of this operation

Exceptions

NullPointerException:: if the specified iterable is null, or if this map does not permit null keys or values, and the specified key or values contain null (optional)

putAll back to summary

putAll	back to summary
public boolean putAll(Map<? extends K, ? extends V> map) Copies all mappings from the specified map to this multi-valued map (optional operation). 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. Parameters map:Map<? extends K, ? extends V> mappings to be stored in this map, may not be null Returns:boolean true if the map changed as a result of this operation Exceptions UnsupportedOperationException: if the `putAll` operation is not supported by this map NullPointerException: if the specified map is null, or if this map does not permit null keys or values, and the specified map contains null keys or values (optional) IllegalArgumentException: if some property of a key or value in the specified map prevents it from being stored in this map

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

Copies all mappings from the specified map to this multi-valued map (optional operation).

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.

Parameters

map:Map<? extends K, ? extends V>: mappings to be stored in this map, may not be null

Returns:boolean

true if the map changed as a result of this operation

Exceptions

UnsupportedOperationException:: if the putAll operation is not supported by this map
NullPointerException:: if the specified map is null, or if this map does not permit null keys or values, and the specified map contains null keys or values (optional)
IllegalArgumentException:: if some property of a key or value in the specified map prevents it from being stored in this map

putAll back to summary

putAll	back to summary
public boolean putAll(MultiValuedMap<? extends K, ? extends V> map) Copies all mappings from the specified map to this multi-valued map (optional operation). 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. Parameters map:MultiValuedMap<? extends K, ? extends V> mappings to be stored in this map, may not be null Returns:boolean true if the map changed as a result of this operation Exceptions UnsupportedOperationException: if the `putAll` operation is not supported by this map NullPointerException: if the specified map is null, or if this map does not permit null keys or values, and the specified map contains null keys or values (optional) IllegalArgumentException: if some property of a key or value in the specified map prevents it from being stored in this map

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

Copies all mappings from the specified map to this multi-valued map (optional operation).

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.

Parameters

map:MultiValuedMap<? extends K, ? extends V>: mappings to be stored in this map, may not be null

Returns:boolean

true if the map changed as a result of this operation

Exceptions

UnsupportedOperationException:: if the putAll operation is not supported by this map
NullPointerException:: if the specified map is null, or if this map does not permit null keys or values, and the specified map contains null keys or values (optional)
IllegalArgumentException:: if some property of a key or value in the specified map prevents it from being stored in this map

remove	back to summary
public Collection<V> remove(Object key) Removes all values associated with the specified key. The returned collection may be modifiable, but updates will not be propagated to this multi-valued map. In case no mapping was stored for the specified key, an empty, unmodifiable collection will be returned. Parameters key:Object the key to remove values from Returns:Collection<V> the values that were removed Exceptions UnsupportedOperationException: if the map is unmodifiable NullPointerException: if the key is null and null keys are invalid (optional)

remove

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public Collection<V> remove(Object key)

Removes all values associated with the specified key.

The returned collection may be modifiable, but updates will not be propagated to this multi-valued map. In case no mapping was stored for the specified key, an empty, unmodifiable collection will be returned.

Parameters

key:Object: the key to remove values from

Returns:Collection<V>

the values that were removed

Exceptions

UnsupportedOperationException:: if the map is unmodifiable
NullPointerException:: if the key is null and null keys are invalid (optional)

removeMapping back to summary

removeMapping	back to summary
public boolean removeMapping(Object key, Object item) Removes a key-value mapping from the 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, implementations typically return an empty collection from a subsequent `get(Object)`. Parameters key:Object the key to remove from item:Object the item to remove Returns:boolean true if the mapping was removed, false otherwise Exceptions UnsupportedOperationException: if the map is unmodifiable NullPointerException: if the key or value is null and null is invalid (optional)

public boolean removeMapping(Object key, Object item)

Removes a key-value mapping from the 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, implementations typically return an empty collection from a subsequent get(Object).

Parameters

key:Object: the key to remove from
item:Object: the item to remove

Returns:boolean

true if the mapping was removed, false otherwise

Exceptions

UnsupportedOperationException:: if the map is unmodifiable
NullPointerException:: if the key or value is null and null is invalid (optional)

size	back to summary
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. Returns:int the total size of the map

size

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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.

Returns:int: the total size of the map

values back to summary

values	back to summary
public Collection<V> values() Gets a `Collection` view of all values contained in this multi-valued map. Implementations typically return a collection containing the combination of values from all keys. Returns:Collection<V> a collection view of the values contained in this multi-valued map

public Collection<V> values()

Gets a Collection view of all values contained in this multi-valued map.

Implementations typically return a collection containing the combination of values from all keys.

Returns:Collection<V>: a collection view of the values contained in this multi-valued map

public Interface MultiValuedMap<K, V>

Method Summary

Method Detail