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/*
Calimero 2 - A library for KNX network access
Copyright (c) 2006, 2011 B. Malinowsky
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
Linking this library statically or dynamically with other modules is
making a combined work based on this library. Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.
As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under terms
of your choice, provided that you also meet, for each linked independent
module, the terms and conditions of the license of that module. An
independent module is a module which is not derived from or based on
this library. If you modify this library, you may extend this exception
to your version of the library, but you are not obligated to do so. If
you do not wish to do so, delete this exception statement from your
version.
*/
package tuwien.auto.calimero.buffer.cache;
/**
* Cache interface to use for different caching policies.
*
* Cache entries are unambiguously identified through a key, as defined by
* {@link CacheObject}.
* For comparison of keys, {@link Object#hashCode()} and
* {@link Object#equals(Object)} are used.
*
* @author B. Malinowsky
* @see CacheObject
*/
public interface Cache
{
/**
* Offers information about data counting and cache performance.
*/
public interface Statistic
{
/**
* Returns the total number of successful requests with
* {@link Cache#get(Object)} for a {@link CacheObject}.
*
*
* @return total hits
*/
long hits();
/**
* Returns the total number of {@link CacheObject} not found with
* {@link Cache#get(Object)}.
*
*
* @return total misses
*/
long misses();
/**
* Returns the ratio between found {@link CacheObject}s to total
* requests through {@link Cache#get(Object)}.
*
* This value is obtained through
* ratio = (hits / (hits + misses)).
*
* @return the hit ratio in the range [0,1]
*/
double hitRatio();
}
/**
* Inserts the {@link CacheObject} obj into the cache.
*
* If a {@link CacheObject} with an equal key (delivered by
* {@link CacheObject#getKey()}) to obj.getKey() is already
* in the cache, it will be replaced by obj.
* {@link CacheObject#resetTimestamp()} is invoked on obj after
* obj was inserted successfully.
*
* @param obj CacheObject to put into the cache
*/
void put(CacheObject obj);
/**
* Gets the {@link CacheObject} associated with key from the
* cache.
*
* If found, the access count of the CacheObject is incremented by 1.
*
* @param key key to search
* @return the CacheObject or null if key does
* not exist in the cache
*/
CacheObject get(Object key);
/**
* Removes the CacheObject associated with key from the cache,
* if found.
*
*
* @param key key of CacheObject to remove
*/
void remove(Object key);
/**
* Removes all {@link CacheObject}s which are not valid anymore, as defined
* by a caching policy, from the cache.
*/
void removeExpired();
/**
* Empties the cache of all {@link CacheObject}s.
*/
void clear();
/**
* Returns information collected by this cache since its creation.
*
*
* @return a {@link Statistic} object
*/
Statistic statistic();
}