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com.hp.hpl.jena.util.cache.RandCache Maven / Gradle / Ivy
Jena is a Java framework for building Semantic Web applications. It provides a programmatic environment for RDF, RDFS and OWL, SPARQL and includes a rule-based inference engine.
/*
* (c) Copyright 2003, 2004, 2005, 2006, 2007, 2008, 2009 Hewlett-Packard Development Company, LP
*
* All rights reserved.
*
* See end of file.
*/
package com.hp.hpl.jena.util.cache;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
*
* @author bwm
*/
public class RandCache implements Cache, CacheControl {
int size;
int threshhold;
boolean enabled = true;
// so we can identify caches
String name; // e.g. when logging
HashMap map;
Collection collection;
protected static Logger logger = LoggerFactory.getLogger(RandCache.class);
long gets = 0;
long puts = 0;
long hits = 0;
/** Creates new RandCache */
RandCache(String name, int size) {
this.size = size;
try {
map = new HashMap(size * 100 / 75); // based on .75 loadfactor
} catch (IllegalArgumentException e) {
if ("Illegal load factor: NaN".equals(e.getMessage())) {
// This strange construction needs explanation.
// When we implemented XSDbase64Binary/XSDhexBinary support involving use
// of byte[] we started seeing this error here. Since the default loadfactor
// is a static final constant in HashMap this should never be possible.
// It only happens under JDK 1.4.1 not under 1.3.1 nor 1.4.2.
// The retry, however does seem to work and hence gives us a work around
// which is completely mysterious but at least enables the unit tests to pass.
// - der 4/5/04
logger.warn("Detected a NaN anomaly believed to be due to use of JDK 1.4.1");
map = new HashMap(size*100/75, 0.75f);
} else {
throw e;
}
}
threshhold = size;
if (threshhold < 2) {
throw new Error("Cache size too small: " + size);
}
collection = map.values();
}
public synchronized Object get(Object key) {
if (enabled) {
if (gets == Long.MAX_VALUE) {
forgetStats();
}
gets++;
Object result = map.get(key);
if (result != null) {
hits++;
}
return result;
} else {
return null;
}
}
public synchronized void put(Object key, Object value) {
// don't allow null values
if (value == null) {
throw new NullPointerException();
}
if (enabled) {
if (puts == Long.MAX_VALUE) {
forgetStats();
}
puts++;
if (map.size() >= threshhold) {
makeSpace();
}
map.put(key, value);
}
}
protected void makeSpace() {
Iterator iter = collection.iterator();
// we are going to remove every 3rd member of the cache
int size = map.size();
int i = 3;
while (i < size ) {
iter.next();
iter.remove();
iter.next();
iter.next();
i = i + 3;
}
}
public synchronized boolean getEnabled() {
return enabled;
}
public synchronized boolean setEnabled(boolean enabled) {
boolean result = enabled;
this.enabled = enabled;
return result;
}
public synchronized void clear() {
map.clear();
}
public synchronized long getHits() {
return hits;
}
public synchronized long getGets() {
return gets;
}
public synchronized long getPuts() {
return puts;
}
protected void forgetStats() {
gets = gets/2;
puts = puts/2;
hits = hits/2;
}
}
/*
* (c) Copyright 2003, 2004, 2005, 2006, 2007, 2008, 2009 Hewlett-Packard Development Company, LP
*
* All rights reserved.
*
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* $Id: RandCache.java,v 1.1 2009/06/29 08:55:53 castagna Exp $
*/
