1// GenericsNote: Converted.
2/*
3 *  Copyright 2003-2004 The Apache Software Foundation
4 *
5 *  Licensed under the Apache License, Version 2.0 (the "License");
6 *  you may not use this file except in compliance with the License.
7 *  You may obtain a copy of the License at
8 *
9 *      http://www.apache.org/licenses/LICENSE-2.0
10 *
11 *  Unless required by applicable law or agreed to in writing, software
12 *  distributed under the License is distributed on an "AS IS" BASIS,
13 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 *  See the License for the specific language governing permissions and
15 *  limitations under the License.
16 */
17package org.jivesoftware.smack.util.collections;
18
19import java.util.Iterator;
20
21/**
22 * Defines an iterator that operates over a <code>Map</code>.
23 * <p/>
24 * This iterator is a special version designed for maps. It can be more
25 * efficient to use this rather than an entry set iterator where the option
26 * is available, and it is certainly more convenient.
27 * <p/>
28 * A map that provides this interface may not hold the data internally using
29 * Map Entry objects, thus this interface can avoid lots of object creation.
30 * <p/>
31 * In use, this iterator iterates through the keys in the map. After each call
32 * to <code>next()</code>, the <code>getValue()</code> method provides direct
33 * access to the value. The value can also be set using <code>setValue()</code>.
34 * <pre>
35 * MapIterator it = map.mapIterator();
36 * while (it.hasNext()) {
37 *   Object key = it.next();
38 *   Object value = it.getValue();
39 *   it.setValue(newValue);
40 * }
41 * </pre>
42 *
43 * @author Matt Hall, John Watkinson, Stephen Colebourne
44 * @version $Revision: 1.1 $ $Date: 2005/10/11 17:05:19 $
45 * @since Commons Collections 3.0
46 */
47public interface MapIterator <K,V> extends Iterator<K> {
48
49    /**
50     * Checks to see if there are more entries still to be iterated.
51     *
52     * @return <code>true</code> if the iterator has more elements
53     */
54    boolean hasNext();
55
56    /**
57     * Gets the next <em>key</em> from the <code>Map</code>.
58     *
59     * @return the next key in the iteration
60     * @throws java.util.NoSuchElementException
61     *          if the iteration is finished
62     */
63    K next();
64
65    //-----------------------------------------------------------------------
66    /**
67     * Gets the current key, which is the key returned by the last call
68     * to <code>next()</code>.
69     *
70     * @return the current key
71     * @throws IllegalStateException if <code>next()</code> has not yet been called
72     */
73    K getKey();
74
75    /**
76     * Gets the current value, which is the value associated with the last key
77     * returned by <code>next()</code>.
78     *
79     * @return the current value
80     * @throws IllegalStateException if <code>next()</code> has not yet been called
81     */
82    V getValue();
83
84    //-----------------------------------------------------------------------
85    /**
86     * Removes the last returned key from the underlying <code>Map</code> (optional operation).
87     * <p/>
88     * This method can be called once per call to <code>next()</code>.
89     *
90     * @throws UnsupportedOperationException if remove is not supported by the map
91     * @throws IllegalStateException         if <code>next()</code> has not yet been called
92     * @throws IllegalStateException         if <code>remove()</code> has already been called
93     *                                       since the last call to <code>next()</code>
94     */
95    void remove();
96
97    /**
98     * Sets the value associated with the current key (optional operation).
99     *
100     * @param value the new value
101     * @return the previous value
102     * @throws UnsupportedOperationException if setValue is not supported by the map
103     * @throws IllegalStateException         if <code>next()</code> has not yet been called
104     * @throws IllegalStateException         if <code>remove()</code> has been called since the
105     *                                       last call to <code>next()</code>
106     */
107    V setValue(V value);
108
109}
110