org.apache.commons.collections.bidimap.TreeBidiMap<K,V>
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java.lang.Object
public class TreeBidiMap<K extends Comparable,V extends Comparable>
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.
| Nested Class Summary |
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| Nested classes/interfaces inherited from interface java.util.Map |
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Map.Entry<K,V> |
| Nested classes/interfaces inherited from interface java.util.Map |
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Map.Entry<K,V> |
| Constructor Summary | |
|---|---|
TreeBidiMap()
Constructs a new empty TreeBidiMap. |
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TreeBidiMap(Map map)
Constructs a new TreeBidiMap by copying an existing Map. |
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| Method Summary | |
|---|---|
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<Map.Entry<K,V>> |
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. |
K |
firstKey()
Gets the first (lowest) key currently in this map. |
V |
get(Object key)
Gets the value to which this map maps the specified key. |
K |
getKey(V 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<V,K> |
inverseBidiMap()
Gets the inverse map for comparison. |
OrderedBidiMap<V,K> |
inverseOrderedBidiMap()
Gets the inverse map for comparison. |
boolean |
isEmpty()
Checks whether the map is empty or not. |
Set<K> |
keySet()
Returns a set view of the keys contained in this map in key order. |
K |
lastKey()
Gets the last (highest) key currently in this map. |
MapIterator<K,V> |
mapIterator()
Gets an iterator over the map entries. |
K |
nextKey(K key)
Gets the next key after the one specified. |
OrderedMapIterator<K,V> |
orderedMapIterator()
Gets an ordered iterator over the map entries. |
K |
previousKey(K key)
Gets the previous key before the one specified. |
V |
put(K key,
V value)
Puts the key-value pair into the map, replacing any previous pair. |
void |
putAll(Map<? extends K,? extends V> map)
Puts all the mappings from the specified map into this map. |
V |
remove(Object key)
Removes the mapping for this key from this map if present. |
K |
removeValue(V 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<V> |
values()
Returns a set view of the values contained in this map in key order. |
| Methods inherited from class java.lang.Object |
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clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
| Constructor Detail |
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public TreeBidiMap()
public TreeBidiMap(Map map)
map - the map to copy
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 |
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public int size()
size in interface Map<K extends Comparable,V extends Comparable>public boolean isEmpty()
isEmpty in interface Map<K extends Comparable,V extends Comparable>public boolean containsKey(Object key)
The key must implement Comparable.
containsKey in interface Map<K extends Comparable,V extends Comparable>key - key whose presence in this map is to be tested
ClassCastException - if the key is of an inappropriate type
NullPointerException - if the key is nullpublic boolean containsValue(Object value)
The value must implement Comparable.
containsValue in interface Map<K extends Comparable,V extends Comparable>value - value whose presence in this map is to be tested
ClassCastException - if the value is of an inappropriate type
NullPointerException - if the value is nullpublic V get(Object key)
The key must implement Comparable.
get in interface Map<K extends Comparable,V extends Comparable>key - key whose associated value is to be returned
ClassCastException - if the key is of an inappropriate type
NullPointerException - if the key is nullpublic V put(K key,
V value)
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.
put in interface Map<K extends Comparable,V extends Comparable>put in interface BidiMap<K extends Comparable,V extends Comparable>key - key with which the specified value is to be associatedvalue - value to be associated with the specified key
ClassCastException - if the key is of an inappropriate type
NullPointerException - if the key is nullpublic void putAll(Map<? extends K,? extends V> map)
All keys and values must implement Comparable.
putAll in interface Map<K extends Comparable,V extends Comparable>map - the map to copy frompublic V remove(Object key)
The key must implement Comparable.
remove in interface Map<K extends Comparable,V extends Comparable>key - key whose mapping is to be removed from the map.
ClassCastException - if the key is of an inappropriate type
NullPointerException - if the key is nullpublic void clear()
clear in interface Map<K extends Comparable,V extends Comparable>public K getKey(V value)
The value must implement Comparable.
getKey in interface BidiMap<K extends Comparable,V extends Comparable>value - value whose associated key is to be returned.
ClassCastException - if the value is of an inappropriate type
NullPointerException - if the value is nullpublic K removeValue(V value)
The value must implement Comparable.
removeValue in interface BidiMap<K extends Comparable,V extends Comparable>value - value whose mapping is to be removed from the map
ClassCastException - if the value is of an inappropriate type
NullPointerException - if the value is nullpublic K firstKey()
firstKey in interface OrderedMap<K extends Comparable,V extends Comparable>NoSuchElementException - if this map is emptypublic K lastKey()
lastKey in interface OrderedMap<K extends Comparable,V extends Comparable>NoSuchElementException - if this map is emptypublic K nextKey(K key)
The key must implement Comparable.
nextKey in interface OrderedMap<K extends Comparable,V extends Comparable>key - the key to search for next from
public K previousKey(K key)
The key must implement Comparable.
previousKey in interface OrderedMap<K extends Comparable,V extends Comparable>key - the key to search for previous from
public Set<K> keySet()
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.
keySet in interface Map<K extends Comparable,V extends Comparable>public Collection<V> values()
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.
values in interface Map<K extends Comparable,V extends Comparable>public Set<Map.Entry<K,V>> entrySet()
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.
entrySet in interface Map<K extends Comparable,V extends Comparable>public MapIterator<K,V> mapIterator()
For this map, this iterator is the fastest way to iterate over the entries.
mapIterator in interface BidiMap<K extends Comparable,V extends Comparable>mapIterator in interface IterableMap<K extends Comparable,V extends Comparable>public OrderedMapIterator<K,V> orderedMapIterator()
This iterator allows both forward and reverse iteration over the entries.
orderedMapIterator in interface OrderedMap<K extends Comparable,V extends Comparable>public BidiMap<V,K> inverseBidiMap()
inverseBidiMap in interface BidiMap<K extends Comparable,V extends Comparable>inverseBidiMap in interface OrderedBidiMap<K extends Comparable,V extends Comparable>public OrderedBidiMap<V,K> inverseOrderedBidiMap()
inverseOrderedBidiMap in interface OrderedBidiMap<K extends Comparable,V extends Comparable>public boolean equals(Object obj)
equals in interface Map<K extends Comparable,V extends Comparable>equals in class Objectobj - the object to compare to
public int hashCode()
hashCode in interface Map<K extends Comparable,V extends Comparable>hashCode in class Objectpublic String toString()
toString in class Object
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