org.apache.commons.collections4.bidimap

## Class DualTreeBidiMap<K,V>

- java.lang.Object
- - org.apache.commons.collections4.bidimap.AbstractDualBidiMap<K,V>
  - - org.apache.commons.collections4.bidimap.DualTreeBidiMap<K,V>

- Type Parameters:
    `K` - the type of the keys in this map
    `V` - the type of the values in this map
  All Implemented Interfaces:
    Serializable, Map<K,V>, SortedMap<K,V>, BidiMap<K,V>, Get<K,V>, IterableGet<K,V>, IterableMap<K,V>, OrderedBidiMap<K,V>, OrderedMap<K,V>, Put<K,V>, SortedBidiMap<K,V>

      public class DualTreeBidiMap<K,V>
      extends AbstractDualBidiMap<K,V>
      implements SortedBidiMap<K,V>, Serializable

  Implementation of `BidiMap` that uses two `TreeMap` instances.

  The setValue() method on iterators will succeed only if the new value being set is not already in the bidimap.

  When considering whether to use this class, the `TreeBidiMap` class should also be considered. It implements the interface using a dedicated design, and does not store each object twice, which can save on memory use.

  NOTE: From Commons Collections 3.1, all subclasses will use `TreeMap` and the flawed `createMap` method is ignored.

  Since:
    3.0
  See Also:
    Serialized Form

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `protected static class` | `DualTreeBidiMap.BidiOrderedMapIterator<K,V>` Inner class MapIterator.
    `protected static class` | `DualTreeBidiMap.ViewMap<K,V>` Internal sorted map view.

    - ### Nested classes/interfaces inherited from class org.apache.commons.collections4.bidimap.AbstractDualBidiMap

      `AbstractDualBidiMap.BidiMapIterator<K,V>, AbstractDualBidiMap.EntrySet<K,V>, AbstractDualBidiMap.EntrySetIterator<K,V>, AbstractDualBidiMap.KeySet<K>, AbstractDualBidiMap.KeySetIterator<K>, AbstractDualBidiMap.MapEntry<K,V>, AbstractDualBidiMap.Values<V>, AbstractDualBidiMap.ValuesIterator<V>, AbstractDualBidiMap.View<K,V,E>`

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

      `Map.Entry<K,V>`

  - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `` | `DualTreeBidiMap()` Creates an empty `DualTreeBidiMap`
    `` | `DualTreeBidiMap(Comparator<? super K> keyComparator, Comparator<? super V> valueComparator)` Constructs a `DualTreeBidiMap` using the specified `Comparator`.
    `` | `DualTreeBidiMap(Map<? extends K,? extends V> map)` Constructs a `DualTreeBidiMap` and copies the mappings from specified `Map`.
    `protected` | `DualTreeBidiMap(Map<K,V> normalMap, Map<V,K> reverseMap, BidiMap<V,K> inverseBidiMap)` Constructs a `DualTreeBidiMap` that decorates the specified maps.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `Comparator<? super K>` | `comparator()`
    `protected DualTreeBidiMap<V,K>` | `createBidiMap(Map<V,K> normalMap, Map<K,V> reverseMap, BidiMap<K,V> inverseMap)` Creates a new instance of this object.
    `K` | `firstKey()` Gets the first key currently in this map.
    `SortedMap<K,V>` | `headMap(K toKey)`
    `SortedBidiMap<V,K>` | `inverseBidiMap()` Gets a view of this map where the keys and values are reversed.
    `OrderedBidiMap<V,K>` | `inverseOrderedBidiMap()`
    `SortedBidiMap<V,K>` | `inverseSortedBidiMap()`
    `K` | `lastKey()` Gets the last key currently in this map.
    `OrderedMapIterator<K,V>` | `mapIterator()` Obtains an ordered map iterator.
    `K` | `nextKey(K key)` Gets the next key after the one specified.
    `K` | `previousKey(K key)` Gets the previous key before the one specified.
    `SortedMap<K,V>` | `subMap(K fromKey, K toKey)`
    `SortedMap<K,V>` | `tailMap(K fromKey)`
    `Comparator<? super V>` | `valueComparator()` Get the comparator used for the values in the value-to-key map aspect.

    - ### Methods inherited from class org.apache.commons.collections4.bidimap.AbstractDualBidiMap

      `clear, containsKey, containsValue, createEntrySetIterator, createKeySetIterator, createValuesIterator, entrySet, equals, get, getKey, hashCode, isEmpty, keySet, put, putAll, remove, removeValue, size, toString, values`

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

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

    - ### Methods inherited from interface org.apache.commons.collections4.BidiMap

      `getKey, put, removeValue, values`

    - ### 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`

    - ### Methods inherited from interface org.apache.commons.collections4.Put

      `clear, putAll`

    - ### Methods inherited from interface org.apache.commons.collections4.Get

      `containsKey, containsValue, entrySet, get, isEmpty, keySet, remove, size`

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

      `entrySet, keySet, values`

- - ### Constructor Detail

    - #### DualTreeBidiMap

          public DualTreeBidiMap()

      Creates an empty `DualTreeBidiMap`

    - #### DualTreeBidiMap

          public DualTreeBidiMap(Map<? extends K,? extends V> map)

      Constructs a `DualTreeBidiMap` and copies the mappings from specified `Map`.
      Parameters:
        `map` - the map whose mappings are to be placed in this map

    - #### DualTreeBidiMap

          public DualTreeBidiMap(Comparator<? super K> keyComparator,
                                 Comparator<? super V> valueComparator)

      Constructs a `DualTreeBidiMap` using the specified `Comparator`.
      Parameters:
        `keyComparator` - the comparator
        `valueComparator` - the values comparator to use

    - #### DualTreeBidiMap

          protected DualTreeBidiMap(Map<K,V> normalMap,
                                    Map<V,K> reverseMap,
                                    BidiMap<V,K> inverseBidiMap)

      Constructs a `DualTreeBidiMap` that decorates the specified maps.
      Parameters:
        `normalMap` - the normal direction map
        `reverseMap` - the reverse direction map
        `inverseBidiMap` - the inverse BidiMap

  - ### Method Detail

    - #### createBidiMap

          protected DualTreeBidiMap<V,K> createBidiMap(Map<V,K> normalMap,
                                                       Map<K,V> reverseMap,
                                                       BidiMap<K,V> inverseMap)

      Creates a new instance of this object.
      Specified by:
        `createBidiMap` in class `AbstractDualBidiMap<K,V>`
      Parameters:
        `normalMap` - the normal direction map
        `reverseMap` - the reverse direction map
        `inverseMap` - the inverse BidiMap
      Returns:
        new bidi map

    - #### comparator

          public Comparator<? super K> comparator()

      Specified by:
        `comparator` in interface `SortedMap<K,V>`

    - #### valueComparator

          public Comparator<? super V> valueComparator()

      Description copied from interface: `SortedBidiMap`
      Get the comparator used for the values in the value-to-key map aspect.
      Specified by:
        `valueComparator` in interface `SortedBidiMap<K,V>`
      Returns:
        Comparator<? super V>

    - #### firstKey

          public K firstKey()

      Description copied from interface: `OrderedMap`
      Gets the first key currently in this map.
      Specified by:
        `firstKey` in interface `SortedMap<K,V>`
      Specified by:
        `firstKey` in interface `OrderedMap<K,V>`
      Returns:
        the first key currently in this map

    - #### lastKey

          public K lastKey()

      Description copied from interface: `OrderedMap`
      Gets the last key currently in this map.
      Specified by:
        `lastKey` in interface `SortedMap<K,V>`
      Specified by:
        `lastKey` in interface `OrderedMap<K,V>`
      Returns:
        the last key currently in this map

    - #### nextKey

          public K nextKey(K key)

      Description copied from interface: `OrderedMap`
      Gets the next key after the one specified.
      Specified by:
        `nextKey` in interface `OrderedMap<K,V>`
      Parameters:
        `key` - the key to search for next from
      Returns:
        the next key, null if no match or at end

    - #### previousKey

          public K previousKey(K key)

      Description copied from interface: `OrderedMap`
      Gets the previous key before the one specified.
      Specified by:
        `previousKey` in interface `OrderedMap<K,V>`
      Parameters:
        `key` - the key to search for previous from
      Returns:
        the previous key, null if no match or at start

    - #### mapIterator

          public OrderedMapIterator<K,V> mapIterator()

      Obtains an ordered map iterator.

      This implementation copies the elements to an ArrayList in order to provide the forward/backward behaviour.

      Specified by:
        `mapIterator` in interface `IterableGet<K,V>`
      Specified by:
        `mapIterator` in interface `OrderedMap<K,V>`
      Overrides:
        `mapIterator` in class `AbstractDualBidiMap<K,V>`
      Returns:
        a new ordered map iterator

    - #### inverseSortedBidiMap

          public SortedBidiMap<V,K> inverseSortedBidiMap()

    - #### inverseOrderedBidiMap

          public OrderedBidiMap<V,K> inverseOrderedBidiMap()

    - #### headMap

          public SortedMap<K,V> headMap(K toKey)

      Specified by:
        `headMap` in interface `SortedMap<K,V>`

    - #### tailMap

          public SortedMap<K,V> tailMap(K fromKey)

      Specified by:
        `tailMap` in interface `SortedMap<K,V>`

    - #### subMap

          public SortedMap<K,V> subMap(K fromKey,
                                       K toKey)

      Specified by:
        `subMap` in interface `SortedMap<K,V>`

    - #### inverseBidiMap

          public SortedBidiMap<V,K> 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<K,V>`
      Specified by:
        `inverseBidiMap` in interface `OrderedBidiMap<K,V>`
      Specified by:
        `inverseBidiMap` in interface `SortedBidiMap<K,V>`
      Overrides:
        `inverseBidiMap` in class `AbstractDualBidiMap<K,V>`
      Returns:
        an inverted bidirectional map

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