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

All Implemented Interfaces:

Map, BidiMap, IterableMap, OrderedBidiMap, OrderedMap
```
public class TreeBidiMap
extends Object
implements OrderedBidiMap
```
Red-Black tree-based implementation of BidiMap where all objects added implement the Comparable interface.
This class guarantees that the map will be in both ascending key order and ascending value order, sorted according to the natural order for the key's and value's classes.
This Map is intended for applications that need to be able to look up a key-value pairing by either key or value, and need to do so with equal efficiency.
While that goal could be accomplished by taking a pair of TreeMaps and redirecting requests to the appropriate TreeMap (e.g., containsKey would be directed to the TreeMap that maps values to keys, containsValue would be directed to the TreeMap that maps keys to values), there are problems with that implementation. If the data contained in the TreeMaps is large, the cost of redundant storage becomes significant. The DualTreeBidiMap and DualHashBidiMap implementations use this approach.
This solution keeps minimizes the data storage by holding data only once. The red-black algorithm is based on java util TreeMap, but has been modified to simultaneously map a tree node by key and by value. This doubles the cost of put operations (but so does using two TreeMaps), and nearly doubles the cost of remove operations (there is a savings in that the lookup of the node to be removed only has to be performed once). And since only one node contains the key and value, storage is significantly less than that required by two TreeMaps.
The Map.Entry instances returned by the appropriate methods will not allow setValue() and will throw an UnsupportedOperationException on attempts to call that method.

Since:

Commons Collections 3.0 (previously DoubleOrderedMap v2.0)

Version:

$Revision: 1713173 $ $Date: 2015-11-07 21:31:09 +0100 (Sat, 07 Nov 2015) $

Author:

Marc Johnson, Stephen Colebourne

Nested Class Summary
- Nested classes/interfaces inherited from interface java.util.Map
  Map.Entry<K extends Object,V extends Object>

Constructor Summary

Constructors
Constructor Description

TreeBidiMap()
Constructs a new empty TreeBidiMap.

TreeBidiMap(Map map)
Constructs a new TreeBidiMap by copying an existing Map.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`clear()`	Removes all mappings from this map.
`boolean`	`containsKey(Object key)`	Checks whether this map contains the a mapping for the specified key.
`boolean`	`containsValue(Object value)`	Checks whether this map contains the a mapping for the specified value.
`Set`	`entrySet()`	Returns a set view of the entries contained in this map in key order.
`boolean`	`equals(Object obj)`	Compares for equals as per the API.
`Object`	`firstKey()`	Gets the first (lowest) key currently in this map.
`Object`	`get(Object key)`	Gets the value to which this map maps the specified key.
`Object`	`getKey(Object value)`	Returns the key to which this map maps the specified value.
`int`	`hashCode()`	Gets the hash code value for this map as per the API.
`BidiMap`	`inverseBidiMap()`	Gets the inverse map for comparison.
`OrderedBidiMap`	`inverseOrderedBidiMap()`	Gets the inverse map for comparison.
`boolean`	`isEmpty()`	Checks whether the map is empty or not.
`Set`	`keySet()`	Returns a set view of the keys contained in this map in key order.
`Object`	`lastKey()`	Gets the last (highest) key currently in this map.
`MapIterator`	`mapIterator()`	Gets an iterator over the map entries.
`Object`	`nextKey(Object key)`	Gets the next key after the one specified.
`OrderedMapIterator`	`orderedMapIterator()`	Gets an ordered iterator over the map entries.
`Object`	`previousKey(Object key)`	Gets the previous key before the one specified.
`Object`	`put(Object key, Object value)`	Puts the key-value pair into the map, replacing any previous pair.
`void`	`putAll(Map map)`	Puts all the mappings from the specified map into this map.
`Object`	`remove(Object key)`	Removes the mapping for this key from this map if present.
`Object`	`removeValue(Object value)`	Removes the mapping for this value from this map if present.
`int`	`size()`	Returns the number of key-value mappings in this map.
`String`	`toString()`	Returns a string version of this Map in standard format.
`Collection`	`values()`	Returns a set view of the values contained in this map in key order.

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map
compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll

- Constructor Detail
  - TreeBidiMap
```
public TreeBidiMap()
```
    Constructs a new empty TreeBidiMap.
  - TreeBidiMap
```
public TreeBidiMap(Map map)
```
    Constructs a new TreeBidiMap by copying an existing Map.
    
    Parameters:
    
    map - the map to copy
    
    Throws:
    
    ClassCastException - if the keys/values in the map are not Comparable or are not mutually comparable
    
    NullPointerException - if any key or value in the map is null
- Method Detail
  - size
```
public int size()
```
    Returns the number of key-value mappings in this map.
    
    Specified by:
    
    size in interface Map
    
    Returns:
    
    the number of key-value mappings in this map
  - isEmpty
```
public boolean isEmpty()
```
    Checks whether the map is empty or not.
    
    Specified by:
    
    isEmpty in interface Map
    
    Returns:
    
    true if the map is empty
  - containsKey
```
public boolean containsKey(Object key)
```
    Checks whether this map contains the a mapping for the specified key.
    The key must implement Comparable.
    
    Specified by:
    
    containsKey in interface Map
    
    Parameters:
    
    key - key whose presence in this map is to be tested
    
    Returns:
    
    true if this map contains a mapping for the specified key
    
    Throws:
    
    ClassCastException - if the key is of an inappropriate type
    
    NullPointerException - if the key is null
  - containsValue
```
public boolean containsValue(Object value)
```
    Checks whether this map contains the a mapping for the specified value.
    The value must implement Comparable.
    
    Specified by:
    
    containsValue in interface Map
    
    Parameters:
    
    value - value whose presence in this map is to be tested
    
    Returns:
    
    true if this map contains a mapping for the specified value
    
    Throws:
    
    ClassCastException - if the value is of an inappropriate type
    
    NullPointerException - if the value is null
  - get
```
public Object get(Object key)
```
    Gets the value to which this map maps the specified key. Returns null if the map contains no mapping for this key.
    The key must implement Comparable.
    
    Specified by:
    
    get in interface Map
    
    Parameters:
    
    key - key whose associated value is to be returned
    
    Returns:
    
    the value to which this map maps the specified key, or null if the map contains no mapping for this key
    
    Throws:
    
    ClassCastException - if the key is of an inappropriate type
    
    NullPointerException - if the key is null
  - put
```
public Object put(Object key,
                  Object value)
```
    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 TreeBidiMap(); 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 TreeBidiMap(); 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
    
    Both key and value must implement Comparable.
    Specified by:
    
    put in interface BidiMap
    
    Specified by:
    
    put in interface Map
    
    Parameters:
    
    key - key with which the specified value is to be associated
    
    value - value to be associated with the specified key
    
    Returns:
    
    the previous value for the key
    
    Throws:
    
    ClassCastException - if the key is of an inappropriate type
    
    NullPointerException - if the key is null
  - putAll
```
public void putAll(Map map)
```
    Puts all the mappings from the specified map into this map.
    All keys and values must implement Comparable.
    
    Specified by:
    
    putAll in interface Map
    
    Parameters:
    
    map - the map to copy from
  - remove
```
public Object remove(Object key)
```
    Removes the mapping for this key from this map if present.
    The key must implement Comparable.
    
    Specified by:
    
    remove in interface Map
    
    Parameters:
    
    key - key whose mapping is to be removed from the map.
    
    Returns:
    
    previous value associated with specified key, or null if there was no mapping for key.
    
    Throws:
    
    ClassCastException - if the key is of an inappropriate type
    
    NullPointerException - if the key is null
  - clear
```
public void clear()
```
    Removes all mappings from this map.
    
    Specified by:
    
    clear in interface Map
  - getKey
```
public Object getKey(Object value)
```
    Returns the key to which this map maps the specified value. Returns null if the map contains no mapping for this value.
    The value must implement Comparable.
    
    Specified by:
    
    getKey in interface BidiMap
    
    Parameters:
    
    value - value whose associated key is to be returned.
    
    Returns:
    
    the key to which this map maps the specified value, or null if the map contains no mapping for this value.
    
    Throws:
    
    ClassCastException - if the value is of an inappropriate type
    
    NullPointerException - if the value is null
  - removeValue
```
public Object removeValue(Object value)
```
    Removes the mapping for this value from this map if present.
    The value must implement Comparable.
    
    Specified by:
    
    removeValue in interface BidiMap
    
    Parameters:
    
    value - value whose mapping is to be removed from the map
    
    Returns:
    
    previous key associated with specified value, or null if there was no mapping for value.
    
    Throws:
    
    ClassCastException - if the value is of an inappropriate type
    
    NullPointerException - if the value is null
  - firstKey
```
public Object firstKey()
```
    Gets the first (lowest) key currently in this map.
    
    Specified by:
    
    firstKey in interface OrderedMap
    
    Returns:
    
    the first (lowest) key currently in this sorted map
    
    Throws:
    
    NoSuchElementException - if this map is empty
  - lastKey
```
public Object lastKey()
```
    Gets the last (highest) key currently in this map.
    
    Specified by:
    
    lastKey in interface OrderedMap
    
    Returns:
    
    the last (highest) key currently in this sorted map
    
    Throws:
    
    NoSuchElementException - if this map is empty
  - nextKey
```
public Object nextKey(Object key)
```
    Gets the next key after the one specified.
    The key must implement Comparable.
    
    Specified by:
    
    nextKey in interface OrderedMap
    
    Parameters:
    
    key - the key to search for next from
    
    Returns:
    
    the next key, null if no match or at end
  - previousKey
```
public Object previousKey(Object key)
```
    Gets the previous key before the one specified.
    The key must implement Comparable.
    
    Specified by:
    
    previousKey in interface OrderedMap
    
    Parameters:
    
    key - the key to search for previous from
    
    Returns:
    
    the previous key, null if no match or at start
  - keySet
```
public Set keySet()
```
    Returns a set view of the keys contained in this map in key order.
    The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress, the results of the iteration are undefined.
    The set supports element removal, which removes the corresponding mapping from the map. It does not support the add or addAll operations.
    
    Specified by:
    
    keySet in interface Map
    
    Returns:
    
    a set view of the keys contained in this map.
  - values
```
public Collection values()
```
    Returns a set view of the values contained in this map in key order. The returned object can be cast to a Set.
    The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress, the results of the iteration are undefined.
    The set supports element removal, which removes the corresponding mapping from the map. It does not support the add or addAll operations.
    
    Specified by:
    
    values in interface Map
    
    Returns:
    
    a set view of the values contained in this map.
  - entrySet
```
public Set entrySet()
```
    Returns a set view of the entries contained in this map in key order. For simple iteration through the map, the MapIterator is quicker.
    The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress, the results of the iteration are undefined.
    The set supports element removal, which removes the corresponding mapping from the map. It does not support the add or addAll operations. The returned MapEntry objects do not support setValue.
    
    Specified by:
    
    entrySet in interface Map
    
    Returns:
    
    a set view of the values contained in this map.
  - mapIterator
```
public MapIterator mapIterator()
```
    Gets an iterator over the map entries.
    For this map, this iterator is the fastest way to iterate over the entries.
    
    Specified by:
    
    mapIterator in interface BidiMap
    
    Specified by:
    
    mapIterator in interface IterableMap
    
    Returns:
    
    an iterator
  - orderedMapIterator
```
public OrderedMapIterator orderedMapIterator()
```
    Gets an ordered iterator over the map entries.
    This iterator allows both forward and reverse iteration over the entries.
    
    Specified by:
    
    orderedMapIterator in interface OrderedMap
    
    Returns:
    
    an iterator
  - inverseBidiMap
```
public BidiMap inverseBidiMap()
```
    Gets the inverse map for comparison.
    
    Specified by:
    
    inverseBidiMap in interface BidiMap
    
    Specified by:
    
    inverseBidiMap in interface OrderedBidiMap
    
    Returns:
    
    the inverse map
  - inverseOrderedBidiMap
```
public OrderedBidiMap inverseOrderedBidiMap()
```
    Gets the inverse map for comparison.
    
    Specified by:
    
    inverseOrderedBidiMap in interface OrderedBidiMap
    
    Returns:
    
    the inverse map
  - equals
```
public boolean equals(Object obj)
```
    Compares for equals as per the API.
    
    Specified by:
    
    equals in interface Map
    
    Overrides:
    
    equals in class Object
    
    Parameters:
    
    obj - the object to compare to
    
    Returns:
    
    true if equal
  - hashCode
```
public int hashCode()
```
    Gets the hash code value for this map as per the API.
    
    Specified by:
    
    hashCode in interface Map
    
    Overrides:
    
    hashCode in class Object
    
    Returns:
    
    the hash code value for this map
  - toString
```
public String toString()
```
    Returns a string version of this Map in standard format.
    
    Overrides:
    
    toString in class Object
    
    Returns:
    
    a standard format string version of the map

Constructor	Description
`TreeBidiMap()`	Constructs a new empty TreeBidiMap.
`TreeBidiMap(Map map)`	Constructs a new TreeBidiMap by copying an existing Map.

Class TreeBidiMap

Nested Class Summary

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

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Map

Constructor Detail

TreeBidiMap

TreeBidiMap

Method Detail

size

isEmpty

containsKey

containsValue

get

put

putAll

remove

clear

getKey

removeValue

firstKey

lastKey

nextKey

previousKey

keySet

values

entrySet

mapIterator

orderedMapIterator

inverseBidiMap

inverseOrderedBidiMap

equals

hashCode

toString