public final class HashMultimap<K,V> extends Object
Multimap using hash tables.
The multimap does not store duplicate key-value pairs. Adding a new key-value pair equal to an existing key-value pair has no effect.
Keys and values may be null. All optional multimap methods are supported, and all returned views are modifiable.
This class is not threadsafe when any concurrent operations update the
multimap. Concurrent read operations will work correctly. To allow concurrent
update operations, wrap your multimap with a call to Multimaps#synchronizedSetMultimap.
| Modifier and Type | Method and Description |
|---|---|
Map<K,Collection<V>> |
asMap()
Returns a view of this multimap as a
Map from each distinct key
to the nonempty collection of that key's associated values. |
void |
clear()
Removes all key-value pairs from the multimap, leaving it empty.
|
boolean |
containsEntry(Object key,
Object value)
Returns
true if this multimap contains at least one key-value pair
with the key key and the value value. |
boolean |
containsKey(Object key)
Returns
true if this multimap contains at least one key-value pair
with the key key. |
boolean |
containsValue(Object value)
Returns
true if this multimap contains at least one key-value pair
with the value value. |
static <K,V> HashMultimap<K,V> |
create()
Creates a new, empty
HashMultimap with the default initial
capacities. |
Set<Map.Entry<K,V>> |
entries()
Returns a view collection of all key-value pairs contained in this
multimap, as
Map.Entry instances. |
boolean |
equals(Object object)
Compares the specified object to this multimap for equality.
|
Set<V> |
get(K key)
Returns a view collection of the values associated with
key in this
multimap, if any. |
int |
hashCode()
Returns the hash code for this multimap.
|
Set<K> |
keySet()
Returns a view collection of all distinct keys contained in this
multimap.
|
boolean |
put(K key,
V value)
Stores a key-value pair in the multimap.
|
boolean |
putAll(K key,
Iterable<? extends V> values)
Stores a key-value pair in this multimap for each of
values, all
using the same key, key. |
boolean |
remove(Object key,
Object value)
Removes a single key-value pair with the key
key and the value
value from this multimap, if such exists. |
Set<V> |
removeAll(Object key)
Removes all values associated with the key
key. |
int |
size()
Returns the number of key-value pairs in this multimap.
|
String |
toString()
Returns a string representation of the multimap, generated by calling
toString on the map returned by Multimap.asMap(). |
Collection<V> |
values()
Returns a view collection containing the value from each key-value
pair contained in this multimap, without collapsing duplicates (so
values().size() == size()). |
clone, finalize, getClass, notify, notifyAll, wait, wait, waitclear, containsEntry, containsKey, containsValue, hashCode, keySet, putAll, remove, size, valuespublic static <K,V> HashMultimap<K,V> create()
HashMultimap with the default initial
capacities.public Set<V> get(K key)
key in this
multimap, if any. Note that when containsKey(key) is false, this
returns an empty collection, not null.
Changes to the returned collection will update the underlying multimap, and vice versa.
The returned collection is not serializable.
Because a SetMultimap has unique values for a given key, this
method returns a Set, instead of the Collection specified
in the Multimap interface.
public Set<Map.Entry<K,V>> entries()
Map.Entry instances.
Changes to the returned collection or the entries it contains will update the underlying multimap, and vice versa. However, adding to the returned collection is not possible.
The iterator generated by the returned collection traverses the values for one key, followed by the values of a second key, and so on.
Each entry is an immutable snapshot of a key-value mapping in the multimap, taken at the time the entry is returned by a method call to the collection or its iterator.
Because a SetMultimap has unique values for a given key, this
method returns a Set, instead of the Collection specified
in the Multimap interface.
public Set<V> removeAll(Object key)
key.
Once this method returns, key will not be mapped to any values,
so it will not appear in Multimap.keySet(), Multimap.asMap(), or any other
views.
The returned collection is immutable.
Because a SetMultimap has unique values for a given key, this
method returns a Set, instead of the Collection specified
in the Multimap interface.
public Map<K,Collection<V>> asMap()
Map from each distinct key
to the nonempty 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 multimap; 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 multimap, and vice versa. The map does not
support put or putAll, nor do its entries support setValue.
Though the method signature doesn't say so explicitly, the returned map
has Set values.
public boolean equals(Object object)
Two SetMultimap instances are equal if, for each key, they
contain the same values. Equality does not depend on the ordering of keys
or values.
public int size()
Multimap
Note: this method does not return the number of distinct
keys in the multimap, which is given by keySet().size() or
asMap().size(). See the opening section of the Multimap
class documentation for clarification.
public boolean containsKey(Object key)
Multimaptrue if this multimap contains at least one key-value pair
with the key key.containsKey in interface Multimap<K,V>public void clear()
Multimappublic Collection<V> values()
values().size() == size()).
Changes to the returned collection will update the underlying multimap, and vice versa. However, adding to the returned collection is not possible.
The iterator generated by the returned collection traverses the values for one key, followed by the values of a second key, and so on.
public boolean containsValue(Object value)
Multimaptrue if this multimap contains at least one key-value pair
with the value value.containsValue in interface Multimap<K,V>public boolean containsEntry(Object key, Object value)
Multimaptrue if this multimap contains at least one key-value pair
with the key key and the value value.containsEntry in interface Multimap<K,V>public boolean remove(Object key, Object value)
Multimapkey and the value
value from this multimap, if such exists. If multiple key-value
pairs in the multimap fit this description, which one is removed is
unspecified.public boolean putAll(K key, Iterable<? extends V> values)
Multimapvalues, all
using the same key, key. Equivalent to (but expected to be more
efficient than):
<p>
for (V value : values) {
put(key, value);
}
In particular, this is a no-op if values is empty.
public Set<K> keySet()
Multimap
Changes to the returned set will update the underlying multimap, and vice versa. However, adding to the returned set is not possible.
public int hashCode()
The hash code of a multimap is defined as the hash code of the map view,
as returned by Multimap.asMap().
public String toString()
toString on the map returned by Multimap.asMap().Copyright © 2007-2024, Oracle and/or its affiliates. All Rights Reserved. Use is subject to license terms.