org.apache.commons.collections.bidimap

## Class AbstractDualBidiMap

- java.lang.Object
- - org.apache.commons.collections.bidimap.AbstractDualBidiMap

- All Implemented Interfaces:
    Map, BidiMap, IterableMap
  Direct Known Subclasses:
    DualHashBidiMap, DualTreeBidiMap

      public abstract class AbstractDualBidiMap
      extends Object
      implements BidiMap

  Abstract `BidiMap` implemented using two maps.

  An implementation can be written simply by implementing the `createMap` method.

  Since:
    Commons Collections 3.0
  Version:
    $Id: AbstractDualBidiMap.java 646777 2008-04-10 12:33:15Z niallp $
  Author:
    Matthew Hawthorne, Stephen Colebourne
  See Also:
    `DualHashBidiMap`, `DualTreeBidiMap`

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `protected static class` | `AbstractDualBidiMap.BidiMapIterator` Inner class MapIterator.
    `protected static class` | `AbstractDualBidiMap.EntrySet` Inner class EntrySet.
    `protected static class` | `AbstractDualBidiMap.EntrySetIterator` Inner class EntrySetIterator.
    `protected static class` | `AbstractDualBidiMap.KeySet` Inner class KeySet.
    `protected static class` | `AbstractDualBidiMap.KeySetIterator` Inner class KeySetIterator.
    `protected static class` | `AbstractDualBidiMap.MapEntry` Inner class MapEntry.
    `protected static class` | `AbstractDualBidiMap.Values` Inner class Values.
    `protected static class` | `AbstractDualBidiMap.ValuesIterator` Inner class ValuesIterator.
    `protected static class` | `AbstractDualBidiMap.View` Inner class View.

    - ### Nested classes/interfaces inherited from interface java.util.Map

      `Map.Entry`

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected Set` | `entrySet` View of the entries.
    `protected BidiMap` | `inverseBidiMap` Inverse view of this map.
    `protected Set` | `keySet` View of the keys.
    `protected Map[]` | `maps` Delegate map array.
    `protected Collection` | `values` View of the values.

  - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `AbstractDualBidiMap()` Creates an empty map, initialised by `createMap`.
    `protected` | `AbstractDualBidiMap(Map normalMap, Map reverseMap)` Creates an empty map using the two maps specified as storage.
    `protected` | `AbstractDualBidiMap(Map normalMap, Map reverseMap, BidiMap inverseBidiMap)` Constructs a map that decorates the specified maps, used by the subclass `createBidiMap` implementation.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `clear()`
    `boolean` | `containsKey(Object key)`
    `boolean` | `containsValue(Object value)`
    `protected abstract BidiMap` | `createBidiMap(Map normalMap, Map reverseMap, BidiMap inverseMap)` Creates a new instance of the subclass.
    `protected Iterator` | `createEntrySetIterator(Iterator iterator)` Creates an entry set iterator.
    `protected Iterator` | `createKeySetIterator(Iterator iterator)` Creates a key set iterator.
    `protected Map` | `createMap()` Deprecated. For constructors, use the new two map constructor. For deserialization, populate the maps array directly in readObject.
    `protected Iterator` | `createValuesIterator(Iterator iterator)` Creates a values iterator.
    `Set` | `entrySet()` Gets an entrySet view of the map.
    `boolean` | `equals(Object obj)`
    `Object` | `get(Object key)`
    `Object` | `getKey(Object value)` Gets the key that is currently mapped to the specified value.
    `int` | `hashCode()`
    `BidiMap` | `inverseBidiMap()` Gets a view of this map where the keys and values are reversed.
    `boolean` | `isEmpty()`
    `Set` | `keySet()` Gets a keySet view of the map.
    `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.
    `void` | `putAll(Map map)`
    `Object` | `remove(Object key)`
    `Object` | `removeValue(Object value)` Removes the key-value pair that is currently mapped to the specified value (optional operation).
    `int` | `size()`
    `String` | `toString()`
    `Collection` | `values()` Gets a values view of the map.

    - ### Methods inherited from class java.lang.Object

      `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- - ### Field Detail

    - #### maps

          protected final transient Map[] maps

      Delegate map array. The first map contains standard entries, and the second contains inverses.

    - #### inverseBidiMap

          protected transient BidiMap inverseBidiMap

      Inverse view of this map.

    - #### keySet

          protected transient Set keySet

      View of the keys.

    - #### values

          protected transient Collection values

      View of the values.

    - #### entrySet

          protected transient Set entrySet

      View of the entries.

  - ### Constructor Detail

    - #### AbstractDualBidiMap

          protected AbstractDualBidiMap()

      Creates an empty map, initialised by `createMap`.

      This constructor remains in place for deserialization. All other usage is deprecated in favour of `AbstractDualBidiMap(Map, Map)`.

    - #### AbstractDualBidiMap

          protected AbstractDualBidiMap(Map normalMap,
                             Map reverseMap)

      Creates an empty map using the two maps specified as storage.

      The two maps must be a matching pair, normal and reverse. They will typically both be empty.

      Neither map is validated, so nulls may be passed in. If you choose to do this then the subclass constructor must populate the `maps[]` instance variable itself.

      Parameters:
        `normalMap` - the normal direction map
        `reverseMap` - the reverse direction map
      Since:
        Commons Collections 3.1

    - #### AbstractDualBidiMap

          protected AbstractDualBidiMap(Map normalMap,
                             Map reverseMap,
                             BidiMap inverseBidiMap)

      Constructs a map that decorates the specified maps, used by the subclass `createBidiMap` implementation.
      Parameters:
        `normalMap` - the normal direction map
        `reverseMap` - the reverse direction map
        `inverseBidiMap` - the inverse BidiMap

  - ### Method Detail

    - #### createMap

          protected Map createMap()

      Deprecated. For constructors, use the new two map constructor. For deserialization, populate the maps array directly in readObject.
      Creates a new instance of the map used by the subclass to store data.

      This design is deeply flawed and has been deprecated. It relied on subclass data being used during a superclass constructor.

      Returns:
        the map to be used for internal storage

    - #### createBidiMap

          protected abstract BidiMap createBidiMap(Map normalMap,
                              Map reverseMap,
                              BidiMap inverseMap)

      Creates a new instance of the subclass.
      Parameters:
        `normalMap` - the normal direction map
        `reverseMap` - the reverse direction map
        `inverseMap` - this map, which is the inverse in the new map
      Returns:
        the inverse map

    - #### get

          public Object get(Object key)

      Specified by:
        `get` in interface `Map`

    - #### size

          public int size()

      Specified by:
        `size` in interface `Map`

    - #### isEmpty

          public boolean isEmpty()

      Specified by:
        `isEmpty` in interface `Map`

    - #### containsKey

          public boolean containsKey(Object key)

      Specified by:
        `containsKey` in interface `Map`

    - #### equals

          public boolean equals(Object obj)

      Specified by:
        `equals` in interface `Map`
      Overrides:
        `equals` in class `Object`

    - #### hashCode

          public int hashCode()

      Specified by:
        `hashCode` in interface `Map`
      Overrides:
        `hashCode` in class `Object`

    - #### toString

          public String toString()

      Overrides:
        `toString` in class `Object`

    - #### put

          public Object put(Object key,
                   Object value)

      Description copied from interface: `BidiMap`
      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 interface `Map`
      Specified by:
        `put` in interface `BidiMap`
      Parameters:
        `key` - the key to store
        `value` - the value to store
      Returns:
        the previous value mapped to this key

    - #### putAll

          public void putAll(Map map)

      Specified by:
        `putAll` in interface `Map`

    - #### remove

          public Object remove(Object key)

      Specified by:
        `remove` in interface `Map`

    - #### clear

          public void clear()

      Specified by:
        `clear` in interface `Map`

    - #### containsValue

          public boolean containsValue(Object value)

      Specified by:
        `containsValue` in interface `Map`

    - #### mapIterator

          public MapIterator mapIterator()

      Obtains a `MapIterator` over the map. The iterator implements `ResetableMapIterator`. This implementation relies on the entrySet iterator.

      The setValue() methods only allow a new value to be set. If the value being set is already in the map, an IllegalArgumentException is thrown (as setValue cannot change the size of the map).

      Specified by:
        `mapIterator` in interface `BidiMap`
      Specified by:
        `mapIterator` in interface `IterableMap`
      Returns:
        a map iterator

    - #### getKey

          public Object getKey(Object value)

      Description copied from interface: `BidiMap`
      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)`.

      Specified by:
        `getKey` in interface `BidiMap`
      Parameters:
        `value` - the value to find the key for
      Returns:
        the mapped key, or `null` if not found

    - #### removeValue

          public Object removeValue(Object value)

      Description copied from interface: `BidiMap`
      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)`.

      Specified by:
        `removeValue` in interface `BidiMap`
      Parameters:
        `value` - the value to find the key-value pair for
      Returns:
        the key that was removed, `null` if nothing removed

    - #### inverseBidiMap

          public BidiMap inverseBidiMap()

      Description copied from interface: `BidiMap`
      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.

      Specified by:
        `inverseBidiMap` in interface `BidiMap`
      Returns:
        an inverted bidirectional map

    - #### keySet

          public Set keySet()

      Gets a keySet view of the map. Changes made on the view are reflected in the map. The set supports remove and clear but not add.
      Specified by:
        `keySet` in interface `Map`
      Returns:
        the keySet view

    - #### createKeySetIterator

          protected Iterator createKeySetIterator(Iterator iterator)

      Creates a key set iterator. Subclasses can override this to return iterators with different properties.
      Parameters:
        `iterator` - the iterator to decorate
      Returns:
        the keySet iterator

    - #### values

          public Collection values()

      Gets a values view of the map. Changes made on the view are reflected in the map. The set supports remove and clear but not add.
      Specified by:
        `values` in interface `Map`
      Returns:
        the values view

    - #### createValuesIterator

          protected Iterator createValuesIterator(Iterator iterator)

      Creates a values iterator. Subclasses can override this to return iterators with different properties.
      Parameters:
        `iterator` - the iterator to decorate
      Returns:
        the values iterator

    - #### entrySet

          public Set entrySet()

      Gets an entrySet view of the map. Changes made on the set are reflected in the map. The set supports remove and clear but not add.

      The Map Entry setValue() method only allow a new value to be set. If the value being set is already in the map, an IllegalArgumentException is thrown (as setValue cannot change the size of the map).

      Specified by:
        `entrySet` in interface `Map`
      Returns:
        the entrySet view

    - #### createEntrySetIterator

          protected Iterator createEntrySetIterator(Iterator iterator)

      Creates an entry set iterator. Subclasses can override this to return iterators with different properties.
      Parameters:
        `iterator` - the iterator to decorate
      Returns:
        the entrySet iterator

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