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org.apache.commons.collections

Interface OrderedMap

All Superinterfaces:
Map, IterableMap

All Known Direct Subinterfaces:
OrderedBidiMap


public interface OrderedMap
implements IterableMap

Defines a map that maintains order and allows both forward and backward iteration through that order.
Since:
Commons Collections 3.0
Author:
Stephen Colebourne

Method Summary

Object

firstKey()

Gets the first key currently in this map.

Object

lastKey()

Gets the last key currently in this map.

Object

nextKey(Object key)

Gets the next key after the one specified.

OrderedMapIterator

orderedMapIterator()

Obtains an OrderedMapIterator over the map.

Object

previousKey(Object key)

Gets the previous key before the one specified.

Method Details

firstKey

public Object firstKey()

Gets the first key currently in this map.

Returns:
the first key currently in this map
Throws:
- 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:
- 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