/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.collections;
/**
* Defines a map that maintains order and allows both forward and backward
* iteration through that order.
*
* @since Commons Collections 3.0
* @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
*
* @author Stephen Colebourne
*/
public interface OrderedMap extends IterableMap {
/**
* Obtains an <code>OrderedMapIterator</code> over the map.
* <p>
* A ordered map iterator is an efficient way of iterating over maps
* in both directions.
* <pre>
* 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();
* }
* </pre>
*
* @return a map iterator
*/
OrderedMapIterator orderedMapIterator();
/**
* Gets the first key currently in this map.
*
* @return the first key currently in this map
* @throws java.util.NoSuchElementException if this map is empty
*/
public Object firstKey();
/**
* Gets the last key currently in this map.
*
* @return the last key currently in this map
* @throws java.util.NoSuchElementException if this map is empty
*/
public Object lastKey();
/**
* Gets the next key after the one specified.
*
* @param key the key to search for next from
* @return the next key, null if no match or at end
*/
public Object nextKey(Object key);
/**
* Gets the previous key before the one specified.
*
* @param key the key to search for previous from
* @return the previous key, null if no match or at start
*/
public Object previousKey(Object key);
}