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Java > Open Source Codes > org > apache > commons > collections > OrderedMap


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 org.apache.commons.collections;
17
18 /**
19  * Defines a map that maintains order and allows both forward and backward
20  * iteration through that order.
21  *
22  * @since Commons Collections 3.0
23  * @version $Revision: 1.6 $ $Date: 2004/02/18 01:15:42 $
24  *
25  * @author Stephen Colebourne
26  */

27 public interface OrderedMap extends IterableMap {
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
33      * in both 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 orderedMapIterator();
48     
49     /**
50      * Gets the first key currently in this map.
51      *
52      * @return the first key currently in this map
53      * @throws java.util.NoSuchElementException if this map is empty
54      */

55     public Object JavaDoc firstKey();
56
57     /**
58      * Gets the last key currently in this map.
59      *
60      * @return the last key currently in this map
61      * @throws java.util.NoSuchElementException if this map is empty
62      */

63     public Object JavaDoc lastKey();
64     
65     /**
66      * Gets the next key after the one specified.
67      *
68      * @param key the key to search for next from
69      * @return the next key, null if no match or at end
70      */

71     public Object JavaDoc nextKey(Object JavaDoc key);
72
73     /**
74      * Gets the previous key before the one specified.
75      *
76      * @param key the key to search for previous from
77      * @return the previous key, null if no match or at start
78      */

79     public Object JavaDoc previousKey(Object JavaDoc key);
80     
81 }
82
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