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comparison src/com/go/trove/util/WrappedCache.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) 1997-2001 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 Map that implements a write-through cache to another map. Two maps are
59 * supplied: one for caching and one for main storage. WrappedCache is not
60 * thread-safe and must be wrapped with Collections.synchronizedMap to be made
61 * thread-safe.
62 *
63 * @author Brian S O'Neill
64 * @version
65 * <!--$$Revision:--> 2 <!-- $-->, <!--$$JustDate:--> 01/07/31 <!-- $-->
66 */
67 public class WrappedCache extends AbstractMap implements Map {
68 private final Map mCacheMap;
69 private final Map mBackingMap;
70
71 /**
72 * @param cacheMap the cache map should offer fast access, but it should
73 * automatically limit its maximum size
74 * @param backingMap the backingMap will be read from only if the requested
75 * entry isn't in the cache
76 */
77 public WrappedCache(Map cacheMap, Map backingMap) {
78 mCacheMap = cacheMap;
79 mBackingMap = backingMap;
80 }
81
82 /**
83 * Returns the size of the backing map.
84 */
85 public int size() {
86 return mBackingMap.size();
87 }
88
89 /**
90 * Returns the empty status of the backing map.
91 */
92 public boolean isEmpty() {
93 return mBackingMap.isEmpty();
94 }
95
96 /**
97 * Returns true if the cache contains the key or else if the backing map
98 * contains the key.
99 */
100 public boolean containsKey(Object key) {
101 return mCacheMap.containsKey(key) || mBackingMap.containsKey(key);
102 }
103
104 /**
105 * Returns true if the cache contains the value or else if the backing map
106 * contains the value.
107 */
108 public boolean containsValue(Object value) {
109 return mCacheMap.containsValue(value) ||
110 mBackingMap.containsValue(value);
111 }
112
113 /**
114 * Returns the value from the cache, or if not found, the backing map.
115 * If the backing map is accessed, the value is saved in the cache for
116 * future gets.
117 */
118 public Object get(Object key) {
119 Object value = mCacheMap.get(key);
120 if (value != null || mCacheMap.containsKey(key)) {
121 return value;
122 }
123 value = mBackingMap.get(key);
124 if (value != null || mBackingMap.containsKey(key)) {
125 mCacheMap.put(key, value);
126 }
127 return value;
128 }
129
130 /**
131 * Puts the entry into both the cache and backing map. The old value in
132 * the backing map is returned.
133 */
134 public Object put(Object key, Object value) {
135 mCacheMap.put(key, value);
136 return mBackingMap.put(key, value);
137 }
138
139 /**
140 * Removes the key from both the cache and backing map. The old value in
141 * the backing map is returned.
142 */
143 public Object remove(Object key) {
144 mCacheMap.remove(key);
145 return mBackingMap.remove(key);
146 }
147
148 /**
149 * Clears both the cache and backing map.
150 */
151 public void clear() {
152 mCacheMap.clear();
153 mBackingMap.clear();
154 }
155
156 /**
157 * Returns the key set of the backing map.
158 */
159 public Set keySet() {
160 return mBackingMap.keySet();
161 }
162
163 /**
164 * Returns the values of the backing map.
165 */
166 public Collection values() {
167 return mBackingMap.values();
168 }
169
170 /**
171 * Returns the entry set of the backing map.
172 */
173 public Set entrySet() {
174 return mBackingMap.entrySet();
175 }
176 }