org.apache.commons.collections.map
Class AbstractLinkedMap

java.lang.Object
  java.util.AbstractMap
      org.apache.commons.collections.map.AbstractHashedMap
          org.apache.commons.collections.map.AbstractLinkedMap

All Implemented Interfaces:

java.util.Map, IterableMap, 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: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $

Author:

java util LinkedHashMap, Stephen Colebourne

Nested Class Summary

protected static class	AbstractLinkedMap.EntrySetIterator EntrySet iterator.
protected static class	AbstractLinkedMap.KeySetIterator KeySet iterator.
protected static class	AbstractLinkedMap.LinkEntry LinkEntry that stores the data.
protected static class	AbstractLinkedMap.LinkIterator Base Iterator that iterates in link order.
protected static class	AbstractLinkedMap.LinkMapIterator MapIterator implementation.
protected static class	AbstractLinkedMap.ValuesIterator Values iterator.

Nested classes/interfaces inherited from class org.apache.commons.collections.map.AbstractHashedMap

AbstractHashedMap.EntrySet, AbstractHashedMap.HashEntry, AbstractHashedMap.HashIterator, AbstractHashedMap.HashMapIterator, AbstractHashedMap.KeySet, AbstractHashedMap.Values

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

java.util.Map.Entry

Field Summary

protected AbstractLinkedMap.LinkEntry

header Header in the linked list

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

data, DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_THRESHOLD, entrySet, GETKEY_INVALID, GETVALUE_INVALID, keySet, loadFactor, MAXIMUM_CAPACITY, modCount, NO_NEXT_ENTRY, NO_PREVIOUS_ENTRY, NULL, REMOVE_INVALID, SETVALUE_INVALID, size, threshold, values

Constructor Summary

protected	AbstractLinkedMap() Constructor only used in deserialization, do not use otherwise.
protected	AbstractLinkedMap(int initialCapacity) Constructs a new, empty map with the specified initial capacity.
protected	AbstractLinkedMap(int initialCapacity, float loadFactor) Constructs a new, empty map with the specified initial capacity and load factor.
protected	AbstractLinkedMap(int initialCapacity, float loadFactor, int threshold) Constructor which performs no validation on the passed in parameters.
protected	AbstractLinkedMap(java.util.Map map) Constructor copying elements from another map.

Method Summary

protected void	addEntry(AbstractHashedMap.HashEntry entry, int hashIndex) Adds an entry into this map, maintaining insertion order.
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.
protected AbstractHashedMap.HashEntry	createEntry(AbstractHashedMap.HashEntry next, int hashCode, java.lang.Object key, java.lang.Object value) Creates an entry to store the data.
protected java.util.Iterator	createEntrySetIterator() Creates an entry set iterator.
protected java.util.Iterator	createKeySetIterator() Creates a key set iterator.
protected java.util.Iterator	createValuesIterator() Creates a values iterator.
protected AbstractLinkedMap.LinkEntry	entryAfter(AbstractLinkedMap.LinkEntry entry) Gets the after field from a LinkEntry.
protected AbstractLinkedMap.LinkEntry	entryBefore(AbstractLinkedMap.LinkEntry entry) Gets the before field from a LinkEntry.
java.lang.Object	firstKey() Gets the first key in the map, which is the most recently inserted.
protected AbstractLinkedMap.LinkEntry	getEntry(int index) Gets the key at the specified index.
protected void	init() Initialise this subclass during construction.
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.
protected void	removeEntry(AbstractHashedMap.HashEntry entry, int hashIndex, AbstractHashedMap.HashEntry previous) Removes an entry from the map and the linked list.

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

addMapping, calculateNewCapacity, calculateThreshold, checkCapacity, clone, containsKey, convertKey, destroyEntry, doReadObject, doWriteObject, ensureCapacity, entryHashCode, entryKey, entryNext, entrySet, entryValue, equals, get, getEntry, hash, hashCode, hashIndex, isEmpty, isEqualKey, isEqualValue, keySet, put, putAll, remove, removeMapping, reuseEntry, size, toString, updateEntry, values

Methods inherited from class java.lang.Object

finalize, 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

Field Detail

header

protected transient AbstractLinkedMap.LinkEntry header

Header in the linked list

Constructor Detail

AbstractLinkedMap

protected AbstractLinkedMap()

Constructor only used in deserialization, do not use otherwise.

AbstractLinkedMap

protected AbstractLinkedMap(int initialCapacity,
                            float loadFactor,
                            int threshold)

Constructor which performs no validation on the passed in parameters.

Parameters:

initialCapacity - the initial capacity, must be a power of two

loadFactor - the load factor, must be > 0.0f and generally < 1.0f

threshold - the threshold, must be sensible

AbstractLinkedMap

protected AbstractLinkedMap(int initialCapacity)

Constructs a new, empty map with the specified initial capacity.

Parameters:

initialCapacity - the initial capacity

Throws:

java.lang.IllegalArgumentException - if the initial capacity is less than one

AbstractLinkedMap

protected AbstractLinkedMap(int initialCapacity,
                            float loadFactor)

Constructs a new, empty map with the specified initial capacity and load factor.

Parameters:

initialCapacity - the initial capacity

loadFactor - the load factor

Throws:

java.lang.IllegalArgumentException - if the initial capacity is less than one

java.lang.IllegalArgumentException - if the load factor is less than zero

AbstractLinkedMap

protected AbstractLinkedMap(java.util.Map map)

Constructor copying elements from another map.

Parameters:

map - the map to copy

Throws:

java.lang.NullPointerException - if the map is null

Method Detail

init

protected void init()

Initialise this subclass during construction.

NOTE: As from v3.2 this method calls AbstractHashedMap.createEntry(HashEntry, int, Object, Object) to create the map entry object.

Overrides:

init in class AbstractHashedMap

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

getEntry

protected AbstractLinkedMap.LinkEntry getEntry(int index)

Gets the key at the specified index.

Parameters:

index - the index to retrieve

Returns:

the key at the specified index

Throws:

java.lang.IndexOutOfBoundsException - if the index is invalid

addEntry

protected void addEntry(AbstractHashedMap.HashEntry entry,
                        int hashIndex)

Adds an entry into this map, maintaining insertion order.

This implementation adds the entry to the data storage table and to the end of the linked list.

Overrides:

addEntry in class AbstractHashedMap

Parameters:

entry - the entry to add

hashIndex - the index into the data array to store at

createEntry

protected AbstractHashedMap.HashEntry createEntry(AbstractHashedMap.HashEntry next,
                                                  int hashCode,
                                                  java.lang.Object key,
                                                  java.lang.Object value)

Creates an entry to store the data.

This implementation creates a new LinkEntry instance.

Overrides:

createEntry in class AbstractHashedMap

Parameters:

next - the next entry in sequence

hashCode - the hash code to use

key - the key to store

value - the value to store

Returns:

the newly created entry

removeEntry

protected void removeEntry(AbstractHashedMap.HashEntry entry,
                           int hashIndex,
                           AbstractHashedMap.HashEntry previous)

Removes an entry from the map and the linked list.

This implementation removes the entry from the linked list chain, then calls the superclass implementation.

Overrides:

removeEntry in class AbstractHashedMap

Parameters:

entry - the entry to remove

hashIndex - the index into the data structure

previous - the previous entry in the chain

entryBefore

protected AbstractLinkedMap.LinkEntry entryBefore(AbstractLinkedMap.LinkEntry entry)

Gets the before field from a LinkEntry. Used in subclasses that have no visibility of the field.

Parameters:

entry - the entry to query, must not be null

Returns:

the before field of the entry

Throws:

java.lang.NullPointerException - if the entry is null

Since:

Commons Collections 3.1

entryAfter

protected AbstractLinkedMap.LinkEntry entryAfter(AbstractLinkedMap.LinkEntry entry)

Gets the after field from a LinkEntry. Used in subclasses that have no visibility of the field.

Parameters:

entry - the entry to query, must not be null

Returns:

the after field of the entry

Throws:

java.lang.NullPointerException - if the entry is null

Since:

Commons Collections 3.1

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

createEntrySetIterator

protected java.util.Iterator createEntrySetIterator()

Creates an entry set iterator. Subclasses can override this to return iterators with different properties.

Overrides:

createEntrySetIterator in class AbstractHashedMap

Returns:

the entrySet iterator

createKeySetIterator

protected java.util.Iterator createKeySetIterator()

Creates a key set iterator. Subclasses can override this to return iterators with different properties.

Overrides:

createKeySetIterator in class AbstractHashedMap

Returns:

the keySet iterator

createValuesIterator

protected java.util.Iterator createValuesIterator()

Creates a values iterator. Subclasses can override this to return iterators with different properties.

Overrides:

createValuesIterator in class AbstractHashedMap

Returns:

the values iterator