org.apache.commons.collections.bidimap

Class AbstractDualBidiMap

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

public abstract class AbstractDualBidiMap
extends java.lang.Object
implements BidiMap

Abstract BidiMap implemented using two maps.

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

Version:
$Id: AbstractDualBidiMap.java,v 1.14 2004/06/22 21:54:35 scolebourne Exp $
Authors:
Matthew Hawthorne
Stephen Colebourne
Since:
Commons Collections 3.0
See Also:
DualHashBidiMap, DualTreeBidiMap

Nested Class Summary

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.

Field Summary

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

AbstractDualBidiMap()
Creates an empty map, initialised by createMap.
AbstractDualBidiMap(Map normalMap, Map reverseMap)
Creates an empty map using the two maps specified as storage.
AbstractDualBidiMap(Map normalMap, Map reverseMap, BidiMap inverseBidiMap)
Constructs a map that decorates the specified maps, used by the subclass createBidiMap implementation.

Method Summary

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.
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.

Field Details

entrySet

protected Set entrySet
View of the entries.

inverseBidiMap

protected BidiMap inverseBidiMap
Inverse view of this map.

keySet

protected Set keySet
View of the keys.

maps

protected final Map[] maps
Delegate map array. The first map contains standard entries, and the second contains inverses.

values

protected Collection values
View of the values.

Constructor Details

AbstractDualBidiMap

protected AbstractDualBidiMap()

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 Details

clear

public void clear()

containsKey

public boolean containsKey(Object key)

containsValue

public boolean containsValue(Object value)

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

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

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

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

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).

Returns:
the entrySet view

equals

public boolean equals(Object obj)

get

public Object get(Object key)

getKey

public Object getKey(Object value)
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

hashCode

public int hashCode()

inverseBidiMap

public BidiMap inverseBidiMap()
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

isEmpty

public boolean isEmpty()

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.
Returns:
the keySet view

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
mapIterator in interface IterableMap
Returns:
a map iterator

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 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 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)

remove

public Object remove(Object key)

removeValue

public Object removeValue(Object value)
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

size

public int size()

toString

public String toString()

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.
Returns:
the values view

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