com.google.common.collect
Class ArrayListMultimap<K,V>

java.lang.Object
  com.google.common.collect.ArrayListMultimap<K,V>

All Implemented Interfaces:

ListMultimap<K,V>, Multimap<K,V>, java.io.Serializable

public final class ArrayListMultimap<K,V>
extends java.lang.Object

Implementation of 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.

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).

Author:

Jared Levy

See Also:

Serialized Form

Constructor Summary

ArrayListMultimap()
Constructs an empty ArrayListMultimap.

ArrayListMultimap(int distinctKeys, int valuesPerKey)
Constructs an empty ArrayListMultimap with the expected number of distinct keys and the expected number of values per distinct key.

ArrayListMultimap(Multimap<? extends K,? extends V> multimap)
Constructs an ArrayListMultimap with the same mappings as the specified Multimap.

Method Summary

java.util.Map<K,java.util.Collection<V>>	asMap() Returns a map view that associates each key with the corresponding values in the multimap.
void	clear() Removes all key-value pairs from the multimap.
boolean	containsEntry(java.lang.Object key, java.lang.Object value) Returns true if the multimap contains the specified key-value pair.
boolean	containsKey(java.lang.Object key) Returns true if the multimap contains any values for the specified key.
boolean	containsValue(java.lang.Object value) Returns true if the multimap contains the specified value for any key.
java.util.Collection<java.util.Map.Entry<K,V>>	entries() Returns a collection of all key-value pairs.
boolean	equals(java.lang.Object obj) Compares the specified object to this multimap for equality.
java.util.List<V>	get(K key) Returns a collection view of all values associated with a key.
int	hashCode() Returns the hash code for this multimap.
boolean	isEmpty() Returns true if the multimap contains no key-value pairs.
Multiset<K>	keys() Returns a collection, which may contain duplicates, of all keys.
java.util.Set<K>	keySet() Returns the set of all keys, each appearing once in the returned set.
boolean	put(K key, V value) Stores a key-value pair in the multimap.
void	putAll(K key, java.lang.Iterable<? extends V> values) Stores a collection of values with the same key.
void	putAll(Multimap<? extends K,? extends V> multimap) Copies all of another multimap's key-value pairs into this multimap.
boolean	remove(java.lang.Object key, java.lang.Object value) Removes a key-value pair from the multimap.
java.util.List<V>	removeAll(java.lang.Object key) Removes all values associated with a given key.
java.util.List<V>	replaceValues(K key, java.lang.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 the multimap.
java.lang.String	toString() Returns a string representation of the multimap, generated by calling toString on the map returned by Multimap.asMap().
void	trimToSize() Reduces the memory used by this ArrayListMultimap, if feasible.
java.util.Collection<V>	values() Returns a collection of all values in the multimap.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface com.google.common.collect.ListMultimap

asMap

Methods inherited from interface com.google.common.collect.Multimap

clear, containsEntry, containsKey, containsValue, entries, hashCode, isEmpty, keys, keySet, putAll, putAll, remove, size, values

Constructor Detail

ArrayListMultimap

public ArrayListMultimap()

Constructs an empty ArrayListMultimap.

ArrayListMultimap

public ArrayListMultimap(int distinctKeys,
                         int valuesPerKey)

Constructs an empty ArrayListMultimap with the expected number of distinct keys and the expected number of values per distinct key.

Parameters:

distinctKeys - the expected number of distinct keys

valuesPerKey - the expected number of values per distinct key

Throws:

java.lang.IllegalArgumentException - if either argument is negative

ArrayListMultimap

public ArrayListMultimap(Multimap<? extends K,? extends V> multimap)

Constructs an ArrayListMultimap with the same mappings as the specified Multimap.

Method Detail

trimToSize

public void trimToSize()

Reduces the memory used by this ArrayListMultimap, if feasible.

get

public java.util.List<V> get(@Nullable
                             K key)

Returns a collection view of all values associated with a key. If no mappings in the multimap have the provided key, an empty collection is returned.

Changes to the returned collection will update the underlying multimap, and vice versa.

The returned collection is not serializable.

Specified by:

get in interface ListMultimap<K,V>

Specified by:

get in interface Multimap<K,V>

Parameters:

key - key to search for in multimap

Returns:

the collection of values that the key maps to

removeAll

public java.util.List<V> removeAll(@Nullable
                                   java.lang.Object key)

Description copied from interface: Multimap

Removes all values associated with a given key.

Specified by:

removeAll in interface ListMultimap<K,V>

Specified by:

removeAll in interface Multimap<K,V>

Parameters:

key - key of entries to remove from the multimap

Returns:

the collection of removed values, or an empty collection if no values were associated with the provided key. The collection is modifiable, but updating it will have no effect on the multimap.

replaceValues

public java.util.List<V> replaceValues(@Nullable
                                       K key,
                                       java.lang.Iterable<? extends V> values)

Description copied from interface: Multimap

Stores a collection of values with the same key, replacing any existing values for that key.

Specified by:

replaceValues in interface ListMultimap<K,V>

Specified by:

replaceValues in interface Multimap<K,V>

Parameters:

key - key to store in the multimap

values - values to store in the multimap

Returns:

the collection of replaced values, or an empty collection if no values were previously associated with the key. The collection is modifiable, but updating it will have no effect on the multimap.

put

public boolean put(@Nullable
                   K key,
                   @Nullable
                   V value)

Stores a key-value pair in the multimap.

Specified by:

put in interface Multimap<K,V>

Parameters:

key - key to store in the multimap

value - value to store in the multimap

Returns:

true always

equals

public boolean equals(@Nullable
                      java.lang.Object obj)

Compares the specified object to this multimap for equality.

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.

Specified by:

equals in interface ListMultimap<K,V>

Specified by:

equals in interface Multimap<K,V>

size

public int size()

Description copied from interface: Multimap

Returns the number of key-value pairs in the multimap.

Specified by:

size in interface Multimap<K,V>

isEmpty

public boolean isEmpty()

Description copied from interface: Multimap

Returns true if the multimap contains no key-value pairs.

Specified by:

isEmpty in interface Multimap<K,V>

containsKey

public boolean containsKey(@Nullable
                           java.lang.Object key)

Description copied from interface: Multimap

Returns true if the multimap contains any values for the specified key.

Specified by:

containsKey in interface Multimap<K,V>

Parameters:

key - key to search for in multimap

containsValue

public boolean containsValue(@Nullable
                             java.lang.Object value)

Description copied from interface: Multimap

Returns true if the multimap contains the specified value for any key.

Specified by:

containsValue in interface Multimap<K,V>

Parameters:

value - value to search for in multimap

containsEntry

public boolean containsEntry(@Nullable
                             java.lang.Object key,
                             @Nullable
                             java.lang.Object value)

Description copied from interface: Multimap

Returns true if the multimap contains the specified key-value pair.

Specified by:

containsEntry in interface Multimap<K,V>

Parameters:

key - key to search for in multimap

value - value to search for in multimap

remove

public boolean remove(@Nullable
                      java.lang.Object key,
                      @Nullable
                      java.lang.Object value)

Description copied from interface: Multimap

Removes a key-value pair from the multimap.

Specified by:

remove in interface Multimap<K,V>

Parameters:

key - key of entry to remove from the multimap

value - value of entry to remove the multimap

Returns:

true if the multimap changed

putAll

public void putAll(@Nullable
                   K key,
                   java.lang.Iterable<? extends V> values)

Description copied from interface: Multimap

Stores a collection of values with the same key.

Specified by:

putAll in interface Multimap<K,V>

Parameters:

key - key to store in the multimap

values - values to store in the multimap

putAll

public void putAll(Multimap<? extends K,? extends V> multimap)

Description copied from interface: Multimap

Copies all of another multimap's key-value pairs into this multimap. The order in which the mappings are added is determined by multimap.entries().

Specified by:

putAll in interface Multimap<K,V>

Parameters:

multimap - mappings to store in this multimap

clear

public void clear()

Description copied from interface: Multimap

Removes all key-value pairs from the multimap.

Specified by:

clear in interface Multimap<K,V>

keySet

public java.util.Set<K> keySet()

Description copied from interface: Multimap

Returns the set of all keys, each appearing once in the returned set. Changes to the returned set will update the underlying multimap, and vice versa.

Specified by:

keySet in interface Multimap<K,V>

Returns:

the collection of distinct keys

keys

public Multiset<K> keys()

Description copied from interface: Multimap

Returns a collection, which may contain duplicates, of all keys. The number of times of key appears in the returned multiset equals the number of mappings the key has in the multimap. Changes to the returned multiset will update the underlying multimap, and vice versa.

Specified by:

keys in interface Multimap<K,V>

Returns:

a multiset with keys corresponding to the distinct keys of the multimap and frequencies corresponding to the number of values that each key maps to

values

public java.util.Collection<V> values()

Returns a collection of all values in the multimap. Changes to the returned collection will update the underlying multimap, and vice versa.

The iterator generated by the returned collection traverses the values for one key, followed by the values of a second key, and so on.

Specified by:

values in interface Multimap<K,V>

Returns:

collection of values, which may include the same value multiple times if it occurs in multiple mappings

entries

public java.util.Collection<java.util.Map.Entry<K,V>> entries()

Returns a collection of all key-value pairs. Changes to the returned collection will update the underlying multimap, and vice versa. The entries collection does not support the add or addAll operations.

The iterator generated by the returned collection traverses the values for one key, followed by the values of a second key, and so on.

Specified by:

entries in interface Multimap<K,V>

Returns:

collection of map entries consisting of key-value pairs

asMap

public java.util.Map<K,java.util.Collection<V>> asMap()

Description copied from interface: Multimap

Returns a map view that associates each key with the corresponding values in the multimap. Changes to the returned map, such as element removal, will update the underlying multimap. The map does not support setValue() on its entries, put, or putAll.

The collections returned by asMap().get(Object) have the same behavior as those returned by Multimap.get(K).

Specified by:

asMap in interface Multimap<K,V>

Returns:

a map view from a key to its collection of values

hashCode

public int hashCode()

Returns the hash code for this multimap.

The hash code of a multimap is defined as the hash code of the map view, as returned by Multimap.asMap().

Specified by:

hashCode in interface Multimap<K,V>

Overrides:

hashCode in class java.lang.Object

See Also:

Map.hashCode()

toString

public java.lang.String toString()

Returns a string representation of the multimap, generated by calling toString on the map returned by Multimap.asMap().

Overrides:

toString in class java.lang.Object

Returns:

a string representation of the multimap