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1   /*
2    *  Copyright 2001-2004 The Apache Software Foundation
3    *
4    *  Licensed under the Apache License, Version 2.0 (the "License");
5    *  you may not use this file except in compliance with the License.
6    *  You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   *  Unless required by applicable law or agreed to in writing, software
11   *  distributed under the License is distributed on an "AS IS" BASIS,
12   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   *  See the License for the specific language governing permissions and
14   *  limitations under the License.
15   */
16  package net.sf.collections15;
17  
18  /***
19   * Defines a map that maintains order and allows both forward and backward
20   * iteration through that order.
21   *
22   * @author Stephen Colebourne
23   * @version $Revision: 1.2 $ $Date: 2004/10/17 01:02:42 $
24   * @since Commons Collections 3.0
25   */
26  public interface OrderedMap <K, V> extends IterableMap<K, V>
27  {
28  
29      /***
30       * Obtains an <code>OrderedMapIterator</code> over the map.
31       * <p/>
32       * A ordered map iterator is an efficient way of iterating over maps in both
33       * directions.
34       * <pre>
35       * BidiMap map = new TreeBidiMap();
36       * MapIterator it = map.mapIterator();
37       * while (it.hasNext()) {
38       *   Object key = it.next();
39       *   Object value = it.getValue();
40       *   it.setValue("newValue");
41       *   Object previousKey = it.previous();
42       * }
43       * </pre>
44       *
45       * @return a map iterator
46       */
47      OrderedMapIterator<K, V> orderedMapIterator();
48  
49      /***
50       * Gets the first key currently in this map.
51       *
52       * @return the first key currently in this map
53       *
54       * @throws java.util.NoSuchElementException
55       *          if this map is empty
56       */
57      K firstKey();
58  
59      /***
60       * Gets the last key currently in this map.
61       *
62       * @return the last key currently in this map
63       *
64       * @throws java.util.NoSuchElementException
65       *          if this map is empty
66       */
67      K lastKey();
68  
69      /***
70       * Gets the next key after the one specified.
71       *
72       * @param key the key to search for next from
73       *
74       * @return the next key, null if no match or at end
75       */
76      K nextKey(Object key);
77  
78      /***
79       * Gets the previous key before the one specified.
80       *
81       * @param key the key to search for previous from
82       *
83       * @return the previous key, null if no match or at start
84       */
85      K previousKey(Object key);
86  }