org.apache.commons.collections.map
Class AbstractLinkedMap

java.lang.Object
  |
  +--org.apache.commons.collections.map.AbstractHashedMap
        |
        +--org.apache.commons.collections.map.AbstractLinkedMap

All Implemented Interfaces:

IterableMap, java.util.Map, OrderedMap

Direct Known Subclasses:

LinkedMap, LRUMap

public class AbstractLinkedMap

extends AbstractHashedMap

implements OrderedMap

An abstract implementation of a hash-based map that links entries to create an ordered map and which provides numerous points for subclasses to override.

This class implements all the features necessary for a subclass linked hash-based map. Key-value entries are stored in instances of the LinkEntry class which can be overridden and replaced. The iterators can similarly be replaced, without the need to replace the KeySet, EntrySet and Values view classes.

Overridable methods are provided to change the default hashing behaviour, and to change how entries are added to and removed from the map. Hopefully, all you need for unusual subclasses is here.

This implementation maintains order by original insertion, but subclasses may work differently. The OrderedMap interface is implemented to provide access to bidirectional iteration and extra convenience methods.

The orderedMapIterator() method provides direct access to a bidirectional iterator. The iterators from the other views can also be cast to OrderedIterator if required.

All the available iterators can be reset back to the start by casting to ResettableIterator and calling reset().

The implementation is also designed to be subclassed, with lots of useful methods exposed.

Since:

Commons Collections 3.0

Version:

$Revision: 1.8 $ $Date: 2004/01/14 21:43:11 $

Author:

java util LinkedHashMap, Stephen Colebourne

Method Summary

void	clear() Clears the map, resetting the size to zero and nullifying references to avoid garbage collection issues.
boolean	containsValue(java.lang.Object value) Checks whether the map contains the specified value.
java.lang.Object	firstKey() Gets the first key in the map, which is the most recently inserted.
java.lang.Object	lastKey() Gets the last key in the map, which is the first inserted.
MapIterator	mapIterator() Gets an iterator over the map.
java.lang.Object	nextKey(java.lang.Object key) Gets the next key in sequence.
OrderedMapIterator	orderedMapIterator() Gets a bidirectional iterator over the map.
java.lang.Object	previousKey(java.lang.Object key) Gets the previous key in sequence.

Methods inherited from class org.apache.commons.collections.map.AbstractHashedMap

containsKey, entrySet, equals, get, hashCode, isEmpty, keySet, put, putAll, remove, size, toString, values

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

containsKey, entrySet, equals, get, hashCode, isEmpty, keySet, put, putAll, remove, size, values

Method Detail

containsValue

public boolean containsValue(java.lang.Object value)

Checks whether the map contains the specified value.

Specified by:

containsValue in interface java.util.Map

Overrides:

containsValue in class AbstractHashedMap

Parameters:

value - the value to search for

Returns:

true if the map contains the value

clear

public void clear()

Clears the map, resetting the size to zero and nullifying references to avoid garbage collection issues.

Specified by:

clear in interface java.util.Map

Overrides:

clear in class AbstractHashedMap

firstKey

public java.lang.Object firstKey()

Gets the first key in the map, which is the most recently inserted.

Specified by:

firstKey in interface OrderedMap

Returns:

the most recently inserted key

lastKey

public java.lang.Object lastKey()

Gets the last key in the map, which is the first inserted.

Specified by:

lastKey in interface OrderedMap

Returns:

the eldest key

nextKey

public java.lang.Object nextKey(java.lang.Object key)

Gets the next key in sequence.

Specified by:

nextKey in interface OrderedMap

Parameters:

key - the key to get after

Returns:

the next key

previousKey

public java.lang.Object previousKey(java.lang.Object key)

Gets the previous key in sequence.

Specified by:

previousKey in interface OrderedMap

Parameters:

key - the key to get before

Returns:

the previous key

mapIterator

public MapIterator mapIterator()

Gets an iterator over the map. Changes made to the iterator affect this map.

A MapIterator returns the keys in the map. It also provides convenient methods to get the key and value, and set the value. It avoids the need to create an entrySet/keySet/values object.

Specified by:

mapIterator in interface IterableMap

Overrides:

mapIterator in class AbstractHashedMap

Returns:

the map iterator

orderedMapIterator

public OrderedMapIterator orderedMapIterator()

Gets a bidirectional iterator over the map. Changes made to the iterator affect this map.

A MapIterator returns the keys in the map. It also provides convenient methods to get the key and value, and set the value. It avoids the need to create an entrySet/keySet/values object.

Specified by:

orderedMapIterator in interface OrderedMap

Returns:

the map iterator