org.apache.commons.collections.map
public class LinkedMap extends AbstractLinkedMap implements Serializable, Cloneable
Map
implementation that maintains the order of the entries.
In this implementation order is maintained by original insertion.
This implementation improves on the JDK1.4 LinkedHashMap by adding the
MapIterator
functionality, additional convenience methods and allowing
bidirectional iteration. It also implements OrderedMap
.
In addition, non-interface methods are provided to access the map by index.
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.
Note that LinkedMap is not synchronized and is not thread-safe. If you wish to use this map from multiple threads concurrently, you must use appropriate synchronization. The simplest approach is to wrap this map using java.util.Collections#synchronizedMap(Map). This class may throw exceptions when accessed by concurrent threads without synchronization.
Since: Commons Collections 3.0
Version: $Revision: 348007 $ $Date: 2005-11-21 22:52:57 +0000 (Mon, 21 Nov 2005) $
Constructor Summary | |
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LinkedMap()
Constructs a new empty map with default size and load factor. | |
LinkedMap(int initialCapacity)
Constructs a new, empty map with the specified initial capacity.
| |
LinkedMap(int initialCapacity, float loadFactor)
Constructs a new, empty map with the specified initial capacity and
load factor.
| |
LinkedMap(Map map)
Constructor copying elements from another map.
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Method Summary | |
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List | asList()
Gets an unmodifiable List view of the keys.
|
Object | clone()
Clones the map without cloning the keys or values.
|
Object | get(int index)
Gets the key at the specified index.
|
Object | getValue(int index)
Gets the value at the specified index.
|
int | indexOf(Object key)
Gets the index of the specified key.
|
Object | remove(int index)
Removes the element at the specified index.
|
Parameters: initialCapacity the initial capacity
Throws: IllegalArgumentException if the initial capacity is less than one
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
Parameters: map the map to copy
Throws: NullPointerException if the map is null
The returned list is unmodifiable because changes to the values of the list (using java.util.ListIterator#set(Object)) will effectively remove the value from the list and reinsert that value at the end of the list, which is an unexpected side effect of changing the value of a list. This occurs because changing the key, changes when the mapping is added to the map and thus where it appears in the list.
An alternative to this method is to use LinkedMap.
Returns: The ordered list of keys.
See Also: LinkedMap
Returns: a shallow clone
Parameters: index the index to retrieve
Returns: the key at the specified index
Throws: IndexOutOfBoundsException if the index is invalid
Parameters: index the index to retrieve
Returns: the key at the specified index
Throws: IndexOutOfBoundsException if the index is invalid
Parameters: key the key to find the index of
Returns: the index, or -1 if not found
Parameters: index the index of the object to remove
Returns: the previous value corresponding the key
,
or null
if none existed
Throws: IndexOutOfBoundsException if the index is invalid