KickJava   Java API By Example, From Geeks To Geeks.

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


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 that orders its elements based on how recently they have been used.
59  * Most recently used elements appear first in the Set. Elements are marked as
60  * being used whenever they are added to the Set. To re-position an element,
61  * re-add it.
62  *
63  * @author Brian S O'Neill
64  * @version
65  * <!--$$Revision:--> 16 <!-- $-->, <!--$$JustDate:--> 9/07/00 <!-- $-->
66  */
67 public class UsageSet extends MapBackedSet {
68     /**
69      * Creates a UsageSet in forward order, MRU first.
70      */
71     public UsageSet() {
72         this(new HashMap());
73     }
74
75     /**
76      * @param backingMap map to use for storage
77      */
78     public UsageSet(Map backingMap) {
79         super(new UsageMap(backingMap));
80     }
81
82     /**
83      * With reverse order, elements are ordered least recently used first. The
84      * ordering of the elements will be consistent with the order they were
85      * added in. Switching to and from reverse order is performed quickly
86      * and is not affected by the current size of the set.
87      */
88     public void setReverseOrder(boolean reverse) {
89         ((UsageMap)mMap).setReverseOrder(reverse);
90     }
91
92     /**
93      * Returns the first element in the set, the most recently used. If reverse
94      * order, then the least recently used is returned.
95      */
96     public Object JavaDoc first() throws NoSuchElementException {
97         return ((UsageMap)mMap).firstKey();
98     }
99
100     /**
101      * Returns the last element in the set, the least recently used. If reverse
102      * order, then the most recently used is returned.
103      */
104     public Object JavaDoc last() throws NoSuchElementException {
105         return ((UsageMap)mMap).lastKey();
106     }
107 }
108
Popular Tags