@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
.
See the Guava User Guide article on Multimap
.
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
ArrayListMultimap with the default initial capacities.
|
static <K |
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 |
create(Multimap
Constructs an
ArrayListMultimap with the same mappings as the specified multimap.
|
Collection |
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.
|
List |
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.
|
List |
removeAll(Object
Removes all values associated with the key
key .
|
List |
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 .
|
void |
trimToSize()
Reduces the memory used by this
ArrayListMultimap , if feasible.
|
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, entries, hashCode, isEmpty, keys, keySet, putAll, putAll, remove, size, values
public static <K,V> ArrayListMultimap <K ,V> create()
ArrayListMultimap
with the default initial capacities.
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.
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> ArrayListMultimap <K ,V> create(Multimap <? extends K ,? extends V> multimap)
ArrayListMultimap
with the same mappings as the specified multimap.
multimap
- the multimap whose contents are copied to this multimap
public void trimToSize()
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.
public List<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 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>
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>
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.
public boolean equals(Objectobject)
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.
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 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 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()
.