org.apache.commons.collections.map
public class ListOrderedMap extends AbstractMapDecorator implements OrderedMap, Serializable
Map
to ensure that the order of addition is retained
using a List
to maintain order.
The order will be used via the iterators and toArray methods on the views.
The order is also returned by the MapIterator
.
The orderedMapIterator()
method accesses an iterator that can
iterate both forwards and backwards through the map.
In addition, non-interface methods are provided to access the map by index.
If an object is added to the Map for a second time, it will remain in the original position in the iteration.
This class is Serializable from Commons Collections 3.1.
Since: Commons Collections 3.0
Version: $Revision: 1.16 $ $Date: 2004/06/07 21:51:39 $
Field Summary | |
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protected List | insertOrder Internal list to hold the sequence of objects |
Constructor Summary | |
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ListOrderedMap()
Constructs a new empty ListOrderedMap that decorates
a HashMap .
| |
protected | ListOrderedMap(Map map)
Constructor that wraps (not copies).
|
Method Summary | |
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List | asList()
Gets an unmodifiable List view of the keys which changes as the map changes.
|
void | clear() |
static OrderedMap | decorate(Map map)
Factory method to create an ordered map.
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Set | entrySet() |
Object | firstKey()
Gets the first key in this map by insert order.
|
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.
|
Set | keySet() |
Object | lastKey()
Gets the last key in this map by insert order.
|
MapIterator | mapIterator() |
Object | nextKey(Object key)
Gets the next key to the one specified using insert order.
|
OrderedMapIterator | orderedMapIterator() |
Object | previousKey(Object key)
Gets the previous key to the one specified using insert order.
|
Object | put(Object key, Object value) |
void | putAll(Map map) |
Object | remove(Object key) |
Object | remove(int index)
Removes the element at the specified index.
|
String | toString()
Returns the Map as a string.
|
Collection | values() |
ListOrderedMap
that decorates
a HashMap
.
Since: Commons Collections 3.1
Parameters: map the map to decorate, must not be null
Throws: IllegalArgumentException if map is null
The returned list is unmodifiable because changes to the values of the list (using {@link 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 {@link #keySet()}.
Returns: The ordered list of keys.
See Also: keySet
An ArrayList
is used to retain order.
Parameters: map the map to decorate, must not be null
Throws: IllegalArgumentException if map is null
Returns: the first key currently in this map
Throws: NoSuchElementException if this map is empty
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
Returns: the last key currently in this map
Throws: NoSuchElementException if this map is empty
Parameters: key the key to find previous for
Returns: the next key, null if no match or at start
Parameters: key the key to find previous for
Returns: the previous key, null if no match or at start
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
Returns: the Map as a String