org.apache.commons.collections.bidimap

## Class UnmodifiableBidiMap

- java.lang.Object
- - org.apache.commons.collections.map.AbstractMapDecorator
  - - org.apache.commons.collections.bidimap.AbstractBidiMapDecorator
    - - org.apache.commons.collections.bidimap.UnmodifiableBidiMap

- All Implemented Interfaces:
    Map, BidiMap, IterableMap, Unmodifiable

      public final class UnmodifiableBidiMap
      extends AbstractBidiMapDecorator
      implements Unmodifiable

  Decorates another `BidiMap` to ensure it can't be altered.
  Since:
    Commons Collections 3.0
  Version:
    $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
  Author:
    Stephen Colebourne

- - ### Nested Class Summary

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

      `Map.Entry`

  - ### Field Summary

    - ### Fields inherited from class org.apache.commons.collections.map.AbstractMapDecorator

      `map`

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `clear()`
    `static BidiMap` | `decorate(BidiMap map)` Factory method to create an unmodifiable map.
    `Set` | `entrySet()`
    `BidiMap` | `inverseBidiMap()` Gets a view of this map where the keys and values are reversed.
    `Set` | `keySet()`
    `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 mapToCopy)`
    `Object` | `remove(Object key)`
    `Object` | `removeValue(Object value)` Removes the key-value pair that is currently mapped to the specified value (optional operation).
    `Collection` | `values()`

    - ### Methods inherited from class org.apache.commons.collections.bidimap.AbstractBidiMapDecorator

      `getBidiMap, getKey`

    - ### Methods inherited from class org.apache.commons.collections.map.AbstractMapDecorator

      `containsKey, containsValue, equals, get, getMap, hashCode, isEmpty, size, toString`

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

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

    - ### Methods inherited from interface java.util.Map

      `containsKey, containsValue, equals, get, hashCode, isEmpty, size`

- - ### Method Detail

    - #### decorate

          public static BidiMap decorate(BidiMap map)

      Factory method to create an unmodifiable map.

      If the map passed in is already unmodifiable, it is returned.

      Parameters:
        `map` - the map to decorate, must not be null
      Returns:
        an unmodifiable BidiMap
      Throws:
        `IllegalArgumentException` - if map is null

    - #### clear

          public void clear()

      Specified by:
        `clear` in interface `Map`
      Overrides:
        `clear` in class `AbstractMapDecorator`

    - #### 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`
      Overrides:
        `put` in class `AbstractMapDecorator`
      Parameters:
        `key` - the key to store
        `value` - the value to store
      Returns:
        the previous value mapped to this key

    - #### putAll

          public void putAll(Map mapToCopy)

      Specified by:
        `putAll` in interface `Map`
      Overrides:
        `putAll` in class `AbstractMapDecorator`

    - #### remove

          public Object remove(Object key)

      Specified by:
        `remove` in interface `Map`
      Overrides:
        `remove` in class `AbstractMapDecorator`

    - #### entrySet

          public Set entrySet()

      Specified by:
        `entrySet` in interface `Map`
      Overrides:
        `entrySet` in class `AbstractMapDecorator`

    - #### keySet

          public Set keySet()

      Specified by:
        `keySet` in interface `Map`
      Overrides:
        `keySet` in class `AbstractMapDecorator`

    - #### values

          public Collection values()

      Specified by:
        `values` in interface `Map`
      Overrides:
        `values` in class `AbstractMapDecorator`

    - #### 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`
      Overrides:
        `removeValue` in class `AbstractBidiMapDecorator`
      Parameters:
        `value` - the value to find the key-value pair for
      Returns:
        the key that was removed, `null` if nothing removed

    - #### mapIterator

          public MapIterator mapIterator()

      Description copied from interface: `BidiMap`
      Obtains a `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");
           }

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

    - #### 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`
      Overrides:
        `inverseBidiMap` in class `AbstractBidiMapDecorator`
      Returns:
        an inverted bidirectional map

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