@GwtCompatible(serializable=true, emulated=true) 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(com.google.common.collect.SetMultimap<K, V>).
| 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(@Nullable Object key,
@Nullable Object value)
Returns
true if this multimap contains at least one key-value pair with the key key and the value value. |
boolean |
containsKey(@Nullable Object key)
Returns
true if this multimap contains at least one key-value pair with the key key. |
boolean |
containsValue(@Nullable 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. |
static <K,V> HashMultimap<K,V> |
create(int expectedKeys,
int expectedValuesPerKey)
Constructs an empty
HashMultimap with enough capacity to hold the specified numbers of
keys and values without rehashing. |
static <K,V> HashMultimap<K,V> |
create(Multimap<? extends K,? extends V> multimap)
Constructs a
HashMultimap with the same mappings as the specified multimap. |
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(@Nullable Object object)
Compares the specified object to this multimap for equality.
|
void |
forEach(BiConsumer<? super K,? super V> action)
Performs the given action for all key-value pairs contained in this multimap.
|
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.
|
boolean |
isEmpty()
Returns
true if this multimap contains no key-value pairs. |
Multiset<K> |
keys()
Returns a view collection containing the key from each key-value pair in this multimap,
without collapsing duplicates.
|
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 |
putAll(Multimap<? extends K,? extends V> multimap)
Stores all key-value pairs of
multimap in this multimap, in the order returned by
multimap.entries(). |
boolean |
remove(@Nullable Object key,
@Nullable 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(@Nullable Object key)
Removes all values associated with the key
key. |
Set<V> |
replaceValues(K key,
Iterable<? extends V> values)
Stores a collection of values with the same key, replacing any existing values for that 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, forEach, hashCode, isEmpty, keys, keySet, putAll, putAll, remove, size, valuespublic static <K,V> HashMultimap<K,V> create()
HashMultimap with the default initial capacities.
This method will soon be deprecated in favor of MultimapBuilder.hashKeys().hashSetValues().build().
public static <K,V> HashMultimap<K,V> create(int expectedKeys, int expectedValuesPerKey)
HashMultimap with enough capacity to hold the specified numbers of
keys and values without rehashing.
This method will soon be deprecated in favor of MultimapBuilder.hashKeys(expectedKeys).hashSetValues(expectedValuesPerKey).build().
expectedKeys - the expected number of distinct keysexpectedValuesPerKey - the expected average number of values per keyIllegalArgumentException - if expectedKeys or expectedValuesPerKey is
negativepublic static <K,V> HashMultimap<K,V> create(Multimap<? extends K,? extends V> multimap)
HashMultimap with the same mappings as the specified multimap. If a
key-value mapping appears multiple times in the input multimap, it only appears once in the
constructed multimap.
This method will soon be deprecated in favor of MultimapBuilder.hashKeys().hashSetValues().build(multimap).
multimap - the multimap whose contents are copied to this multimappublic 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.
get in interface Multimap<K,V>get in interface SetMultimap<K,V>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.
entries in interface Multimap<K,V>entries in interface SetMultimap<K,V>@CanIgnoreReturnValue public Set<V> removeAll(@Nullable 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.
removeAll in interface Multimap<K,V>removeAll in interface SetMultimap<K,V>@CanIgnoreReturnValue public Set<V> replaceValues(K key, Iterable<? extends V> values)
If values is empty, this is equivalent to removeAll(key).
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.
Any duplicates in values will be stored in the multimap once.
replaceValues in interface Multimap<K,V>replaceValues in interface SetMultimap<K,V>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.
asMap in interface Multimap<K,V>asMap in interface SetMultimap<K,V>@CanIgnoreReturnValue public boolean put(K key, V value)
public boolean equals(@Nullable 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.
equals in interface Multimap<K,V>equals in interface SetMultimap<K,V>object - the reference object with which to compare.true if this object is the same as the obj
argument; false otherwise.Object.hashCode(),
HashMappublic int size()
MultimapNote: 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(@Nullable 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 void forEach(BiConsumer<? super K,? super V> action)
MultimapMultimap implementation, actions will be performed in the order of
iteration of Multimap.entries(). Exceptions thrown by the action are relayed to the caller.
To loop over all keys and their associated value collections, write Multimaps.asMap(multimap).forEach((key, valueCollection) -> action()).
public boolean isEmpty()
Multimaptrue if this multimap contains no key-value pairs. Equivalent to size()
== 0, but can in some cases be more efficient.public boolean containsValue(@Nullable 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(@Nullable Object key, @Nullable 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>@CanIgnoreReturnValue public boolean remove(@Nullable Object key, @Nullable 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.@CanIgnoreReturnValue 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):
for (V value : values) {
put(key, value);
}
In particular, this is a no-op if values is empty.
@CanIgnoreReturnValue public boolean putAll(Multimap<? extends K,? extends V> multimap)
Multimapmultimap in this multimap, in the order returned by
multimap.entries().public Set<K> keySet()
MultimapChanges to the returned set will update the underlying multimap, and vice versa. However, adding to the returned set is not possible.
public Multiset<K> keys()
Multimapkeys().count(k) == get(k).size() for all k.
Changes to the returned multiset will update the underlying multimap, and vice versa. However, adding to the returned collection 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().
hashCode in interface Multimap<K,V>hashCode in class ObjectMap.hashCode()public String toString()
toString on the
map returned by Multimap.asMap().Copyright © 2010–2020. All rights reserved.