AbstractLinkedMap (Apache Commons Collections 3.2.2 API)

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

All Implemented Interfaces:

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: 972404 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $

Author:

java util LinkedHashMap, Stephen Colebourne

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`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 class java.util.AbstractMap
AbstractMap.SimpleEntry, AbstractMap.SimpleImmutableEntry

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

Field Summary

Fields
Modifier and Type Field and Description

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

Fields
Modifier and Type	Field and Description
`protected AbstractLinkedMap.LinkEntry`	`header` Header in the linked list

Constructor Summary

Constructors
Modifier	Constructor and Description
`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(Map map)` Constructor copying elements from another map.

Method Summary

Methods
Modifier and Type	Method and Description
`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(Object value)` Checks whether the map contains the specified value.
`protected AbstractHashedMap.HashEntry`	`createEntry(AbstractHashedMap.HashEntry next, int hashCode, Object key, Object value)` Creates an entry to store the data.
`protected Iterator`	`createEntrySetIterator()` Creates an entry set iterator.
`protected Iterator`	`createKeySetIterator()` Creates a key set iterator.
`protected 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`.
`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.
`Object`	`lastKey()` Gets the last key in the map, which is the first inserted.
`MapIterator`	`mapIterator()` Gets an iterator over the map.
`Object`	`nextKey(Object key)` Gets the next key in sequence.
`OrderedMapIterator`	`orderedMapIterator()` Gets a bidirectional iterator over the map.
`Object`	`previousKey(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:
    
    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:
    
    IllegalArgumentException - if the initial capacity is less than one
    
    IllegalArgumentException - if the load factor is less than zero
  - AbstractLinkedMap
```
protected AbstractLinkedMap(Map map)
```
    Constructor copying elements from another map.
    
    Parameters:
    map - the map to copy
    
    Throws:
    
    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(Object value)
```
    Checks whether the map contains the specified value.
    
    Specified by:
    
    containsValue in interface 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 Map
    
    Overrides:
    
    clear in class AbstractHashedMap
  - firstKey
```
public 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 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 Object nextKey(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 Object previousKey(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:
    
    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,
                                      Object key,
                                      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:
    
    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:
    
    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 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 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 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

Class AbstractLinkedMap

Nested Class Summary

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

Nested classes/interfaces inherited from class java.util.AbstractMap

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

Field Summary

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

Constructor Summary

Method Summary

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

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Map

Field Detail

header

Constructor Detail

AbstractLinkedMap

AbstractLinkedMap

AbstractLinkedMap

AbstractLinkedMap

AbstractLinkedMap

Method Detail

init

containsValue

clear

firstKey

lastKey

nextKey

previousKey

getEntry

addEntry

createEntry

removeEntry

entryBefore

entryAfter

mapIterator

orderedMapIterator

createEntrySetIterator

createKeySetIterator

createValuesIterator