KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > com > go > trove > util > MapBackedSet


1 /* ====================================================================
2  * Trove - Copyright (c) 1997-2000 Walt Disney Internet Group
3  * ====================================================================
4  * The Tea Software License, Version 1.1
5  *
6  * Copyright (c) 2000 Walt Disney Internet Group. All rights reserved.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  *
12  * 1. Redistributions of source code must retain the above copyright
13  * notice, this list of conditions and the following disclaimer.
14  *
15  * 2. Redistributions in binary form must reproduce the above copyright
16  * notice, this list of conditions and the following disclaimer in
17  * the documentation and/or other materials provided with the
18  * distribution.
19  *
20  * 3. The end-user documentation included with the redistribution,
21  * if any, must include the following acknowledgment:
22  * "This product includes software developed by the
23  * Walt Disney Internet Group (http://opensource.go.com/)."
24  * Alternately, this acknowledgment may appear in the software itself,
25  * if and wherever such third-party acknowledgments normally appear.
26  *
27  * 4. The names "Tea", "TeaServlet", "Kettle", "Trove" and "BeanDoc" must
28  * not be used to endorse or promote products derived from this
29  * software without prior written permission. For written
30  * permission, please contact opensource@dig.com.
31  *
32  * 5. Products derived from this software may not be called "Tea",
33  * "TeaServlet", "Kettle" or "Trove", nor may "Tea", "TeaServlet",
34  * "Kettle", "Trove" or "BeanDoc" appear in their name, without prior
35  * written permission of the Walt Disney Internet Group.
36  *
37  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
38  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
39  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
40  * DISCLAIMED. IN NO EVENT SHALL THE WALT DISNEY INTERNET GROUP OR ITS
41  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
42  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
43  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
44  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
45  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
46  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
47  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
48  * ====================================================================
49  *
50  * For more information about Tea, please see http://opensource.go.com/.
51  */
52
53 package com.go.trove.util;
54
55 import java.util.*;
56
57 /******************************************************************************
58  * A set implementation that is backed by any map.
59  *
60  * @author Brian S O'Neill
61  * @version
62  * <!--$$Revision:--> 12 <!-- $-->, <!--$$JustDate:--> 9/07/00 <!-- $-->
63  */
64 public class MapBackedSet extends AbstractSet implements java.io.Serializable JavaDoc {
65     // Dummy value to associate with an Object in the backing Map
66 private static final Object JavaDoc PRESENT = new Object JavaDoc();
67
68     protected final Map mMap;
69
70     /**
71      * @param map The map to back this set.
72      */
73     public MapBackedSet(Map map) {
74         mMap = map;
75     }
76
77     /**
78      * Returns an iterator over the elements in this set. The elements
79      * are returned in the order determined by the backing map.
80      *
81      * @return an Iterator over the elements in this set.
82      * @see ConcurrentModificationException
83      */
84     public Iterator iterator() {
85         return mMap.keySet().iterator();
86     }
87
88     /**
89      * Returns the number of elements in this set (its cardinality).
90      *
91      * @return the number of elements in this set (its cardinality).
92      */
93     public int size() {
94         return mMap.size();
95     }
96
97     /**
98      * Returns true if this set contains no elements.
99      *
100      * @return true if this set contains no elements.
101      */
102     public boolean isEmpty() {
103         return mMap.isEmpty();
104     }
105
106     /**
107      * Returns true if this set contains the specified element.
108      *
109      * @return true if this set contains the specified element.
110      */
111     public boolean contains(Object JavaDoc obj) {
112         return mMap.containsKey(obj);
113     }
114
115     /**
116      * Adds the specified element to this set if it is not already
117      * present.
118      *
119      * @param obj element to be added to this set.
120      * @return true if the set did not already contain the specified element.
121      */
122     public boolean add(Object JavaDoc obj) {
123         return mMap.put(obj, PRESENT) == null;
124     }
125
126     /**
127      * Removes the given element from this set if it is present.
128      *
129      * @param obj object to be removed from this set, if present.
130      * @return true if the set contained the specified element.
131      */
132     public boolean remove(Object JavaDoc obj) {
133         return mMap.remove(obj) == PRESENT;
134     }
135
136     /**
137      * Removes all of the elements from this set.
138      */
139     public void clear() {
140         mMap.clear();
141     }
142 }
143
Popular Tags