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(Object, Object) method description for more information.
| Method Summary | |
|---|---|
| Object |
Gets the key that is currently mapped to the specified value. |
| BidiMap |
Gets a view of this map where the keys and values are reversed. |
| MapIterator |
Obtains a MapIterator over the map.
|
| Object |
Puts the key-value pair into the map, replacing any previous pair. |
| Object |
Removes the key-value pair that is currently mapped to the specified value (optional operation). |
| Methods inherited from java.utilMap |
|---|
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.
public
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");
}
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
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).
If the value is not contained in the map,
nullis returned.Implementations should seek to make this method perform equally as well as
get(Object).