org.apache.commons.collections4

Interface SetValuedMap<K,V>

Type Parameters:

K - the type of the keys in this map

V - the type of the values in this map

All Superinterfaces:

MultiValuedMap<K,V>

All Known Implementing Classes:

AbstractSetValuedMap, HashSetValuedHashMap

public interface SetValuedMap<K,V>
extends MultiValuedMap<K,V>

Defines a map that holds a set of values against each key.

A SetValuedMap is a Map with slightly different semantics:

• Putting a value into the map will add the value to a Set at that key.
• Getting a value will return a Set, holding all the values put to that key.

Since:

4.1

Method Summary

Modifier and Type	Method and Description
Set<V>	get(K key) Gets the set of values associated with the specified key.
Set<V>	remove(Object key) Removes all values associated with the specified key.

Methods inherited from interface org.apache.commons.collections4.MultiValuedMap

asMap, clear, containsKey, containsMapping, containsValue, entries, isEmpty, keys, keySet, mapIterator, put, putAll, putAll, putAll, removeMapping, size, values

Method Detail

get

Set<V> get(K key)

Gets the set of values associated with the specified key.

Implementations typically return an empty Set if no values have been mapped to the key.

Specified by:

get in interface MultiValuedMap<K,V>

Parameters:

key - the key to retrieve

Returns:

the Set of values, implementations should return an empty Set for no mapping

Throws:

NullPointerException - if the key is null and null keys are invalid

remove

Set<V> remove(Object key)

Removes all values associated with the specified key.

The returned set may be modifiable, but updates will not be propagated to this set-valued map. In case no mapping was stored for the specified key, an empty, unmodifiable set will be returned.

Specified by:

remove in interface MultiValuedMap<K,V>

Parameters:

key - the key to remove values from

Returns:

the Set of values removed, implementations should return null for no mapping found, but may return an empty collection

Throws:

UnsupportedOperationException - if the map is unmodifiable

NullPointerException - if the key is null and null keys are invalid