com.google.common.collect

Interface SetMultimap<K,V>

All Superinterfaces:

Multimap<K,V>

All Known Subinterfaces:

SortedSetMultimap<K,V>

All Known Implementing Classes:

ForwardingSetMultimap, ForwardingSortedSetMultimap, HashMultimap, ImmutableSetMultimap, LinkedHashMultimap, TreeMultimap

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

A Multimap that cannot hold duplicate key-value pairs. Adding a key-value pair that's already in the multimap has no effect. 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 Set of values, while entries() returns a Set of map entries. Though the method signature doesn't say so explicitly, the map returned by asMap() has Set values.

If the values corresponding to a single key should be ordered according to a Comparator (or the natural order), see the SortedSetMultimap subinterface.

Since the value collections are sets, the behavior of a SetMultimap is not specified if key or value objects already present in the multimap change in a manner that affects equals comparisons. Use caution if mutable objects are used as keys or values in a SetMultimap.

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.
Set<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 obj) Compares the specified object to this multimap for equality.
Set<V>	get(K key) Returns a view collection of the values associated with key in this multimap, if any.
Set<V>	removeAll(@Nullable Object key) Removes all values associated with the key key.
Set<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, forEach, hashCode, isEmpty, keys, keySet, put, putAll, putAll, remove, size, values

Method Detail

get

Set<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 a SetMultimap has unique values for a given key, this method returns a Set, instead of the Collection specified in the Multimap interface.

Specified by:

get in interface Multimap<K,V>

removeAll

@CanIgnoreReturnValue
Set<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 a SetMultimap has unique values for a given key, this method returns a Set, 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
Set<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 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.

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.

entries

Set<Map.Entry<K,V>> entries()

Returns a view collection of all key-value pairs contained in this multimap, as 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.

Because a SetMultimap has unique values for a given key, this method returns a Set, instead of the Collection specified in the Multimap interface.

Specified by:

entries in interface Multimap<K,V>

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 Set. To obtain this map with the more specific generic type Map<K, Set<V>>, call Multimaps.asMap(SetMultimap) 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 SetMultimap instances are equal if, for each key, they contain the same values. Equality does not depend on the ordering of keys or values.

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

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