public interface BidiMap extends IterableMap
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(java.lang.Object, java.lang.Object) method description for more information.
| Modifier and Type | Method and Description |
|---|---|
Object |
getKey(Object value)
Gets the key that is currently mapped to the specified value.
|
BidiMap |
inverseBidiMap()
Gets a view of this map where the keys and values are reversed.
|
MapIterator |
mapIterator()
Obtains a
MapIterator over the map. |
Object |
put(Object key,
Object value)
Puts the key-value pair into the map, replacing any previous pair.
|
Object |
removeValue(Object value)
Removes the key-value pair that is currently mapped to the specified
value (optional operation).
|
MapIterator mapIterator()
MapIterator over the map.
A map iterator is an efficient way of iterating over maps. It does not require that the map is stored using Map Entry objects which can increase performance.
BidiMap map = new DualHashBidiMap();
MapIterator it = map.mapIterator();
while (it.hasNext()) {
Object key = it.next();
Object value = it.getValue();
it.setValue("newValue");
}
mapIterator in interface IterableMapObject put(Object key, Object value)
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
put in interface Mapkey - the key to storevalue - the value to storeUnsupportedOperationException - if the put 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 specifiedObject getKey(Object 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).
value - the value to find the key fornull if not foundClassCastException - (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 specifiedObject removeValue(Object 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 remove(Object).
value - the value to find the key-value pair fornull if nothing removedClassCastException - (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 implementationBidiMap inverseBidiMap()
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.
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