@GwtCompatible(serializable=true, emulated=true) public final class ArrayListMultimap<K,V> extends Object
Multimap
that uses an ArrayList
to store the values for a given
key. A HashMap
associates each key with an ArrayList
of values.
When iterating through the collections supplied by this class, the ordering of values for a given key agrees with the order in which the values were added.
This multimap allows duplicate key-value pairs. After adding a new key-value pair equal to an
existing key-value pair, the ArrayListMultimap
will contain entries for both the new
value and the old value.
Keys and values may be null. All optional multimap methods are supported, and all returned views are modifiable.
The lists returned by get(K)
, removeAll(java.lang.Object)
, and replaceValues(K, java.lang.Iterable<? extends V>)
all
implement RandomAccess
.
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.synchronizedListMultimap(com.google.common.collect.ListMultimap<K, V>)
.
See the Guava User Guide article on Multimap
.
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> ArrayListMultimap<K,V> |
create()
Creates a new, empty
ArrayListMultimap with the default initial capacities. |
static <K,V> ArrayListMultimap<K,V> |
create(int expectedKeys,
int expectedValuesPerKey)
Constructs an empty
ArrayListMultimap with enough capacity to hold the specified
numbers of keys and values without resizing. |
static <K,V> ArrayListMultimap<K,V> |
create(Multimap<? extends K,? extends V> multimap)
Constructs an
ArrayListMultimap with the same mappings as the specified multimap. |
Collection<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.
|
List<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. |
List<V> |
removeAll(@Nullable Object key)
Removes all values associated with the key
key . |
List<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() . |
void |
trimToSize()
Deprecated.
For a
ListMultimap that automatically trims to size, use ImmutableListMultimap . If you need a mutable collection, remove the trimToSize
call, or switch to a HashMap<K, ArrayList<V>> . |
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() ). |
public static <K,V> ArrayListMultimap<K,V> create()
ArrayListMultimap
with the default initial capacities.
This method will soon be deprecated in favor of MultimapBuilder.hashKeys().arrayListValues().build()
.
public static <K,V> ArrayListMultimap<K,V> create(int expectedKeys, int expectedValuesPerKey)
ArrayListMultimap
with enough capacity to hold the specified
numbers of keys and values without resizing.
This method will soon be deprecated in favor of MultimapBuilder.hashKeys(expectedKeys).arrayListValues(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> ArrayListMultimap<K,V> create(Multimap<? extends K,? extends V> multimap)
ArrayListMultimap
with the same mappings as the specified multimap.
This method will soon be deprecated in favor of MultimapBuilder.hashKeys().arrayListValues().build(multimap)
.
multimap
- the multimap whose contents are copied to this multimap@Deprecated public void trimToSize()
ListMultimap
that automatically trims to size, use ImmutableListMultimap
. If you need a mutable collection, remove the trimToSize
call, or switch to a HashMap<K, ArrayList<V>>
.ArrayListMultimap
, if feasible.public List<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 the values for a given key may have duplicates and follow the insertion ordering,
this method returns a List
, instead of the Collection
specified in the Multimap
interface.
get
in interface ListMultimap<K,V>
get
in interface Multimap<K,V>
@CanIgnoreReturnValue public List<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 the values for a given key may have duplicates and follow the insertion ordering,
this method returns a List
, instead of the Collection
specified in the Multimap
interface.
removeAll
in interface ListMultimap<K,V>
removeAll
in interface Multimap<K,V>
@CanIgnoreReturnValue public List<V> replaceValues(K key, Iterable<? extends V> values)
If values
is empty, this is equivalent to removeAll(key)
.
The returned collection is immutable.
Because the values for a given key may have duplicates and follow the insertion ordering,
this method returns a List
, instead of the Collection
specified in the Multimap
interface.
replaceValues
in interface ListMultimap<K,V>
replaceValues
in interface Multimap<K,V>
@CanIgnoreReturnValue public boolean put(K key, V value)
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 List
values.
asMap
in interface ListMultimap<K,V>
asMap
in interface Multimap<K,V>
public boolean equals(@Nullable Object object)
Two ListMultimap
instances are equal if, for each key, they contain the same values
in the same order. If the value orderings disagree, the multimaps will not be considered equal.
equals
in interface ListMultimap<K,V>
equals
in interface Multimap<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()
,
HashMap
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(@Nullable Object key)
Multimap
true
if this multimap contains at least one key-value pair with the key key
.containsKey
in interface Multimap<K,V>
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 Collection<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.
public void forEach(BiConsumer<? super K,? super V> action)
Multimap
Multimap
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()
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(@Nullable Object value)
Multimap
true
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)
Multimap
true
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)
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.@CanIgnoreReturnValue 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.
@CanIgnoreReturnValue 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.asMap()
.
hashCode
in interface Multimap<K,V>
hashCode
in class Object
Map.hashCode()
public String toString()
toString
on the
map returned by Multimap.asMap()
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