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comparison src/com/go/trove/util/UsageSet.java @ 0:3dc0c5604566

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Initial checkin of blitz 2.0 fcs - no installer yet.
author Dan Creswell <dan.creswell@gmail.com>
date Sat, 21 Mar 2009 11:00:06 +0000
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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 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 last() throws NoSuchElementException {
105 return ((UsageMap)mMap).lastKey();
106 }
107 }