View Javadoc
1 package org.apache.turbine.util; 2 3 /* ==================================================================== 4 * The Apache Software License, Version 1.1 5 * 6 * Copyright (c) 2001 The Apache Software Foundation. All rights 7 * reserved. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in 18 * the documentation and/or other materials provided with the 19 * distribution. 20 * 21 * 3. The end-user documentation included with the redistribution, 22 * if any, must include the following acknowledgment: 23 * "This product includes software developed by the 24 * Apache Software Foundation (http://www.apache.org/)." 25 * Alternately, this acknowledgment may appear in the software itself, 26 * if and wherever such third-party acknowledgments normally appear. 27 * 28 * 4. The names "Apache" and "Apache Software Foundation" and 29 * "Apache Turbine" must not be used to endorse or promote products 30 * derived from this software without prior written permission. For 31 * written permission, please contact apache@apache.org. 32 * 33 * 5. Products derived from this software may not be called "Apache", 34 * "Apache Turbine", nor may "Apache" appear in their name, without 35 * prior written permission of the Apache Software Foundation. 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 APACHE SOFTWARE FOUNDATION OR 41 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 42 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 43 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF 44 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 45 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 46 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 47 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 48 * SUCH DAMAGE. 49 * ==================================================================== 50 * 51 * This software consists of voluntary contributions made by many 52 * individuals on behalf of the Apache Software Foundation. For more 53 * information on the Apache Software Foundation, please see 54 * <http://www.apache.org/>;. 55 */ 56 57 58 /*** 59 * A fixed length object cache implementing the LRU algorithm. Convenient for 60 * buffering recently used objects. 61 * 62 * @author <a href="mailto:dlr@collab.net">Daniel Rall</a> 63 * @version $Id: BufferCache.java,v 1.2 2002/07/11 16:53:21 mpoeschl Exp $ 64 */ 65 public class BufferCache extends SequencedHashtable 66 { 67 /*** 68 * The default maximum cache size. 69 */ 70 private static final int DEFAULT_MAX_SIZE = 35; 71 72 /*** 73 * The size of the cache. The newest elements in the sequence are kept 74 * toward the end. 75 */ 76 private int maxSize; 77 78 /*** 79 * Creates a new instance with default storage buffer pre-allocated. 80 */ 81 public BufferCache() 82 { 83 this(DEFAULT_MAX_SIZE); 84 } 85 86 /*** 87 * Creates a new instance with the specified storage buffer pre-allocated. 88 * 89 * @param maxSize The maximum size of the cache. 90 */ 91 public BufferCache(int maxSize) 92 { 93 super(maxSize); 94 this.maxSize = maxSize; 95 } 96 97 /*** 98 * Stores the provided key/value pair, freshening its list index if the 99 * specified key already exists. 100 * 101 * @param key The key to the provided value. 102 * @param value The value to store. 103 * @return The previous value for the specified key, or 104 * <code>null</code> if none. 105 */ 106 public synchronized Object put(Object key, Object value) 107 { 108 int size = size(); 109 if (size > 0 && size + 1 >= maxSize) 110 { 111 // Stay within constraints of allocated buffer by releasing the 112 // eldest buffered object. 113 remove(0); 114 } 115 return super.put(key, value); 116 } 117 118 /*** 119 * Retrieves the value associated with the provided key, freshening the 120 * sequence of the key as well. 121 * 122 * @param key The key whose value to retrieve. 123 * @return The keyed value. 124 */ 125 public synchronized Object get(Object key) 126 { 127 Object value = super.get(key); 128 if (value != null) 129 { 130 freshenSequence(key, value); 131 } 132 return value; 133 } 134 }

This page was automatically generated by Maven