@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
.
Modifier and Type | Method and Description |
---|---|
Map |
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
Returns
true if this multimap contains at least one key-value pair with the key
key and the value
value .
|
boolean |
containsKey(Object
Returns
true if this multimap contains at least one key-value pair with the key
key .
|
boolean |
containsValue(Object
Returns
true if this multimap contains at least one key-value pair with the value
value .
|
static <K |
create()
Creates a new, empty
HashMultimap with the default initial capacities.
|
static <K |
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 |
create(Multimap
Constructs a
HashMultimap with the same mappings as the specified multimap.
|
Set |
entries()
Returns a view collection of all key-value pairs contained in this multimap, as
Map.Entry instances.
|
boolean |
equals(Object
Compares the specified object to this multimap for equality.
|
Set |
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 |
keys()
Returns a view collection containing the key from each key-value pair in this multimap,
without collapsing duplicates.
|
Set |
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
Stores a key-value pair in this multimap for each of
values , all using the same key,
key .
|
boolean |
putAll(Multimap
Stores all key-value pairs of
multimap in this multimap, in the order returned by
multimap.entries() .
|
boolean |
remove(Object
Removes a single key-value pair with the key
key and the value
value from this multimap, if such exists.
|
Set |
removeAll(Object
Removes all values associated with the key
key .
|
Set |
replaceValues(K key, Iterable
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 .
|
Collection |
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, wait
clear, containsEntry, containsKey, containsValue, hashCode, isEmpty, keys, keySet, putAll, putAll, remove, size, values
public static <K,V> HashMultimap <K ,V> create()
HashMultimap
with the default initial capacities.
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.
expectedKeys
- the expected number of distinct keys
expectedValuesPerKey
- the expected average number of values per key
IllegalArgumentException
- if
expectedKeys
or
expectedValuesPerKey
is negative
public 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.
multimap
- the multimap whose contents are copied to this multimap
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
, Multimap
, 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>
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.
public boolean put(K key, V value)
public boolean equals(Objectobject)
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(Objectkey)
Multimap
true
if this multimap contains at least one key-value pair with the key
key
.
public void clear()
Multimap
public 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 isEmpty()
Multimap
true
if this multimap contains no key-value pairs. Equivalent to
size() == 0
, but can in some cases be more efficient.
public boolean containsValue(Objectvalue)
Multimap
true
if this multimap contains at least one key-value pair with the value
value
.
public boolean containsEntry(Objectkey, Object value)
Multimap
true
if this multimap contains at least one key-value pair with the key
key
and the value
value
.
public boolean remove(Objectkey, Object value)
Multimap
key
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)
Multimap
values
, 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.
public boolean putAll(Multimap<? extends K ,? extends V> multimap)
Multimap
multimap
in this multimap, in the order returned by
multimap.entries()
.
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 Multiset<K> keys()
Multimap
keys().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
.
hashCode
in interface
Multimap<K,V>
hashCode
in class
Object
Map.hashCode()
public StringtoString()
toString
on the map returned by
Multimap.asMap()
.