com.google.common.collect

Interface ListMultimap<K,V>

All Superinterfaces:

Multimap<K,V>

All Known Implementing Classes:

ArrayListMultimap, ForwardingListMultimap, ImmutableListMultimap, LinkedListMultimap

@GwtCompatible
public interface ListMultimap<K,V>
extends Multimap<K,V>

A Multimap that can hold duplicate key-value pairs and that maintains the insertion ordering of values for a given key. See the Multimap documentation for information common to all multimaps.

The get(K), removeAll(java.lang.Object), and replaceValues(K, java.lang.Iterable<? extends V>) methods each return a List of values. Though the method signature doesn't say so explicitly, the map returned by asMap() has List values.

See the Guava User Guide article on Multimap.

Since:

2.0

Author:

Jared Levy

Method Summary

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.
boolean	equals(@Nullable Object obj) Compares the specified object to this multimap for equality.
List<V>	get(K key) Returns a view collection of the values associated with key in this multimap, if any.
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.

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

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

Method Detail

get

List<V> get(K key)

Returns a view collection of the values associated with 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.

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.

Specified by:

get in interface Multimap<K,V>

removeAll

@CanIgnoreReturnValue
List<V> removeAll(@Nullable Object key)

Removes all values associated with the 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.

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.

Specified by:

removeAll in interface Multimap<K,V>

Returns:

the values that were removed (possibly empty). The returned collection may be modifiable, but updating it will have no effect on the multimap.

replaceValues

@CanIgnoreReturnValue
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.

If values is empty, this is equivalent to removeAll(key).

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.

Specified by:

replaceValues in interface Multimap<K,V>

Returns:

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

asMap

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. 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.

Note: The returned map's values are guaranteed to be of type List. To obtain this map with the more specific generic type Map<K, List<V>>, call Multimaps.asMap(ListMultimap) instead.

Specified by:

asMap in interface Multimap<K,V>

equals

boolean equals(@Nullable 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.

An empty ListMultimap is equal to any other empty Multimap, including an empty SetMultimap.

Specified by:

equals in interface Multimap<K,V>

Overrides:

equals in class Object

Parameters:

obj - the reference object with which to compare.

Returns:

true if this object is the same as the obj argument; false otherwise.

See Also:

Object.hashCode(), HashMap