org.apache.commons.collections

Interface OrderedMap

public interface OrderedMap extends IterableMap

Defines a map that maintains order and allows both forward and backward iteration through that order.

Since: Commons Collections 3.0

Version: $Revision: 155406 $ $Date: 2005-02-26 12:55:26 +0000 (Sat, 26 Feb 2005) $

Author: Stephen Colebourne

Method Summary
ObjectfirstKey()
Gets the first key currently in this map.
ObjectlastKey()
Gets the last key currently in this map.
ObjectnextKey(Object key)
Gets the next key after the one specified.
OrderedMapIteratororderedMapIterator()
Obtains an OrderedMapIterator over the map.
ObjectpreviousKey(Object key)
Gets the previous key before the one specified.

Method Detail

firstKey

public Object firstKey()
Gets the first key currently in this map.

Returns: the first key currently in this map

Throws: java.util.NoSuchElementException if this map is empty

lastKey

public Object lastKey()
Gets the last key currently in this map.

Returns: the last key currently in this map

Throws: java.util.NoSuchElementException if this map is empty

nextKey

public Object nextKey(Object key)
Gets the next key after the one specified.

Parameters: key the key to search for next from

Returns: the next key, null if no match or at end

orderedMapIterator

public OrderedMapIterator orderedMapIterator()
Obtains an OrderedMapIterator over the map.

A ordered map iterator is an efficient way of iterating over maps in both directions.

 BidiMap map = new TreeBidiMap();
 MapIterator it = map.mapIterator();
 while (it.hasNext()) {
   Object key = it.next();
   Object value = it.getValue();
   it.setValue("newValue");
   Object previousKey = it.previous();
 }
 

Returns: a map iterator

previousKey

public Object previousKey(Object key)
Gets the previous key before the one specified.

Parameters: key the key to search for previous from

Returns: the previous key, null if no match or at start

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