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 (imported from Google Collections Library)

Author:

Jared Levy

Method Summary

Methods

Modifier and Type	Method and Description
Map<K,Collection<V>>	asMap() Returns a map view that associates each key with the corresponding values in the multimap.
Set<Map.Entry<K,V>>	entries() Returns a collection of all key-value pairs.
boolean	equals(Object obj) Compares the specified object to this multimap for equality.
Set<V>	get(K key) Returns a collection view containing the values associated with key in this multimap, if any.
Set<V>	removeAll(Object key) Removes all values associated with a given 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, hashCode, isEmpty, keys, keySet, put, putAll, putAll, remove, size, values

Method Detail

get

Set<V> get(@Nullable
         K key)

Returns a collection view containing the values associated with key in this multimap, if any. Note that even when (containsKey(key) is false, get(key) still 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>

Parameters:

key - key to search for in multimap

Returns:

a view collection containing the zero or more values that the key maps to

removeAll

Set<V> removeAll(@Nullable
               Object key)

Removes all values associated with a given 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>

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 may be modifiable, but updating it will have no effect on the multimap.

replaceValues

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>

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 may be modifiable, but updating it will have no effect on the multimap.

entries

Set<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.

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>

Returns:

collection of map entries consisting of key-value pairs

asMap

Map<K,Collection<V>> asMap()

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.

When passed a key that is present in the map, asMap().get(Object) has the same behavior as Multimap.get(K), returning a live collection. When passed a key that is not present, however, asMap().get(Object) returns null instead of an empty collection.

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>

Returns:

a map view from a key to its collection of values

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