001: /*
002: * $Id: GenericCache.java,v 1.8 2003/11/07 20:16:25 dfs Exp $
003: *
004: * ====================================================================
005: * The Apache Software License, Version 1.1
006: *
007: * Copyright (c) 2000 The Apache Software Foundation. All rights
008: * reserved.
009: *
010: * Redistribution and use in source and binary forms, with or without
011: * modification, are permitted provided that the following conditions
012: * are met:
013: *
014: * 1. Redistributions of source code must retain the above copyright
015: * notice, this list of conditions and the following disclaimer.
016: *
017: * 2. Redistributions in binary form must reproduce the above copyright
018: * notice, this list of conditions and the following disclaimer in
019: * the documentation and/or other materials provided with the
020: * distribution.
021: *
022: * 3. The end-user documentation included with the redistribution,
023: * if any, must include the following acknowledgment:
024: * "This product includes software developed by the
025: * Apache Software Foundation (http://www.apache.org/)."
026: * Alternately, this acknowledgment may appear in the software itself,
027: * if and wherever such third-party acknowledgments normally appear.
028: *
029: * 4. The names "Apache" and "Apache Software Foundation", "Jakarta-Oro"
030: * must not be used to endorse or promote products derived from this
031: * software without prior written permission. For written
032: * permission, please contact apache@apache.org.
033: *
034: * 5. Products derived from this software may not be called "Apache"
035: * or "Jakarta-Oro", nor may "Apache" or "Jakarta-Oro" appear in their
036: * name, without prior written permission of the Apache Software Foundation.
037: *
038: * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
039: * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
040: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
041: * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
042: * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
043: * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
044: * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
045: * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
046: * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
047: * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
048: * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
049: * SUCH DAMAGE.
050: * ====================================================================
051: *
052: * This software consists of voluntary contributions made by many
053: * individuals on behalf of the Apache Software Foundation. For more
054: * information on the Apache Software Foundation, please see
055: * <http://www.apache.org/>.
056: */
057:
058: package org.apache.oro.util;
059:
060: import java.util.*;
061:
062: /**
063: * This is the base class for all cache implementations provided in the
064: * org.apache.oro.util package. To derive a subclass from GenericCache
065: * only the ... methods
066: * need be overridden.
067: * Although 4 subclasses of GenericCache are provided with this
068: * package, users may not derive subclasses from this class.
069: * Rather, users should create their own implmentations of the
070: * {@link Cache} interface.
071: *
072: * @version @version@
073: * @since 1.0
074: * @see Cache
075: * @see CacheLRU
076: * @see CacheFIFO
077: * @see CacheFIFO2
078: * @see CacheRandom
079: */
080: public abstract class GenericCache implements Cache,
081: java.io.Serializable {
082: /**
083: * The default capacity to be used by the GenericCache subclasses
084: * provided with this package. Its value is 20.
085: */
086: public static final int DEFAULT_CAPACITY = 20;
087:
088: int _numEntries;
089: GenericCacheEntry[] _cache;
090: HashMap _table;
091:
092: /**
093: * The primary constructor for GenericCache. It has default
094: * access so it will only be used within the package. It initializes
095: * _table to a Hashtable of capacity equal to the capacity argument,
096: * _cache to an array of size equal to the capacity argument, and
097: * _numEntries to 0.
098: * <p>
099: * @param capacity The maximum capacity of the cache.
100: */
101: GenericCache(int capacity) {
102: _numEntries = 0;
103: _table = new HashMap(capacity);
104: _cache = new GenericCacheEntry[capacity];
105:
106: while (--capacity >= 0)
107: _cache[capacity] = new GenericCacheEntry(capacity);
108: }
109:
110: public abstract void addElement(Object key, Object value);
111:
112: public synchronized Object getElement(Object key) {
113: Object obj;
114:
115: obj = _table.get(key);
116:
117: if (obj != null)
118: return ((GenericCacheEntry) obj)._value;
119:
120: return null;
121: }
122:
123: public final Iterator keys() {
124: return _table.keySet().iterator();
125: }
126:
127: /**
128: * Returns the number of elements in the cache, not to be confused with
129: * the {@link #capacity()} which returns the number
130: * of elements that can be held in the cache at one time.
131: * <p>
132: * @return The current size of the cache (i.e., the number of elements
133: * currently cached).
134: */
135: public final int size() {
136: return _numEntries;
137: }
138:
139: /**
140: * Returns the maximum number of elements that can be cached at one time.
141: * <p>
142: * @return The maximum number of elements that can be cached at one time.
143: */
144: public final int capacity() {
145: return _cache.length;
146: }
147:
148: public final boolean isFull() {
149: return (_numEntries >= _cache.length);
150: }
151: }
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