Interface BidiMap<K,V>
- Type Parameters:
K
- the type of the keys in the mapV
- the type of the values in the map
- All Superinterfaces:
Get<K,
,V> IterableGet<K,
,V> IterableMap<K,
,V> Map<K,
,V> Put<K,
V>
- All Known Subinterfaces:
OrderedBidiMap<K,
,V> SortedBidiMap<K,
V>
- All Known Implementing Classes:
AbstractBidiMapDecorator
,AbstractDualBidiMap
,AbstractOrderedBidiMapDecorator
,AbstractSortedBidiMapDecorator
,DualHashBidiMap
,DualLinkedHashBidiMap
,DualTreeBidiMap
,TreeBidiMap
,UnmodifiableBidiMap
,UnmodifiableOrderedBidiMap
,UnmodifiableSortedBidiMap
This extended Map
represents a mapping where a key may
lookup a value and a value may lookup a key with equal ease.
This interface extends Map
and so may be used anywhere a map
is required. The interface provides an inverse map view, enabling
full access to both directions of the BidiMap
.
Implementations should allow a value to be looked up from a key and a key to be looked up from a value with equal performance.
This map enforces the restriction that there is a 1:1 relation between
keys and values, meaning that multiple keys cannot map to the same value.
This is required so that "inverting" the map results in a map without
duplicate keys. See the put(K, V)
method description for more information.
- Since:
- 3.0
-
Nested Class Summary
-
Method Summary
Modifier and TypeMethodDescriptionGets the key that is currently mapped to the specified value.Gets a view of this map where the keys and values are reversed.Puts the key-value pair into the map, replacing any previous pair.removeValue
(Object value) Removes the key-value pair that is currently mapped to the specified value (optional operation).values()
Returns aSet
view of the values contained in this map.Methods inherited from interface org.apache.commons.collections4.Get
containsKey, containsValue, entrySet, get, isEmpty, keySet, remove, size
Methods inherited from interface org.apache.commons.collections4.IterableGet
mapIterator
Methods inherited from interface java.util.Map
clear, compute, computeIfAbsent, computeIfPresent, containsKey, containsValue, entrySet, equals, forEach, get, getOrDefault, hashCode, isEmpty, keySet, merge, putAll, putIfAbsent, remove, remove, replace, replace, replaceAll, size
-
Method Details
-
getKey
Gets the key that is currently mapped to the specified value.If the value is not contained in the map,
null
is returned.Implementations should seek to make this method perform equally as well as
get(Object)
.- Parameters:
value
- the value to find the key for- Returns:
- the mapped key, or
null
if not found - Throws:
ClassCastException
- (optional) if the map limits the type of the value and the specified value is inappropriateNullPointerException
- (optional) if the map limits the values to non-null and null was specified
-
inverseBidiMap
BidiMap<V,K> inverseBidiMap()Gets a view of this map where the keys and values are reversed.Changes to one map will be visible in the other and vice versa. This enables both directions of the map to be accessed as a
Map
.Implementations should seek to avoid creating a new object every time this method is called. See
AbstractMap.values()
etc. Calling this method on the inverse map should return the original.- Returns:
- an inverted bidirectional map
-
put
Puts the key-value pair into the map, replacing any previous pair.When adding a key-value pair, the value may already exist in the map against a different key. That mapping is removed, to ensure that the value only occurs once in the inverse map.
BidiMap map1 = new DualHashBidiMap(); map.put("A","B"); // contains A mapped to B, as per Map map.put("A","C"); // contains A mapped to C, as per Map BidiMap map2 = new DualHashBidiMap(); map.put("A","B"); // contains A mapped to B, as per Map map.put("C","B"); // contains C mapped to B, key A is removed
- Specified by:
put
in interfaceMap<K,
V> - Specified by:
put
in interfacePut<K,
V> - Parameters:
key
- the key to storevalue
- the value to store- Returns:
- the previous value mapped to this key
- Throws:
UnsupportedOperationException
- if theput
method is not supportedClassCastException
- (optional) if the map limits the type of the value and the specified value is inappropriateIllegalArgumentException
- (optional) if the map limits the values in some way and the value was invalidNullPointerException
- (optional) if the map limits the values to non-null and null was specified- See Also:
-
removeValue
Removes the key-value pair that is currently mapped to the specified value (optional operation).If the value is not contained in the map,
null
is returned.Implementations should seek to make this method perform equally as well as
remove(Object)
.- Parameters:
value
- the value to find the key-value pair for- Returns:
- the key that was removed,
null
if nothing removed - Throws:
ClassCastException
- (optional) if the map limits the type of the value and the specified value is inappropriateNullPointerException
- (optional) if the map limits the values to non-null and null was specifiedUnsupportedOperationException
- if this method is not supported by the implementation
-
values
Returns aSet
view of the values contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's ownremove
operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via theIterator.remove
,Collection.remove
,removeAll
,retainAll
andclear
operations. It does not support theadd
oraddAll
operations.
-