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/**
* JDBM LICENSE v1.00
*
* Redistribution and use of this software and associated documentation
* ("Software"), with or without modification, are permitted provided
* that the following conditions are met:
*
* 1. Redistributions of source code must retain copyright
* statements and notices. Redistributions must also contain a
* copy of this document.
*
* 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 "JDBM" must not be used to endorse or promote
* products derived from this Software without prior written
* permission of Cees de Groot. For written permission,
* please contact cg@cdegroot.com.
*
* 4. Products derived from this Software may not be called "JDBM"
* nor may "JDBM" appear in their names without prior written
* permission of Cees de Groot.
*
* 5. Due credit should be given to the JDBM Project
* (http://jdbm.sourceforge.net/).
*
* THIS SOFTWARE IS PROVIDED BY THE JDBM PROJECT AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESSED 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
* CEES DE GROOT OR ANY CONTRIBUTORS 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.
*
* Copyright 2000 (C) Cees de Groot. All Rights Reserved.
* Contributions are Copyright (C) 2000 by their associated contributors.
*
* $Id: CachePolicy.java,v 1.5 2003/11/01 13:25:02 dranatunga Exp $
*/
package jdbm.helper;
import java.util.Enumeration;
/**
* CachePolicity is an abstraction for different cache policies.
* (ie. MRU, time-based, soft-refs, ...)
*
* @author <a href="mailto:boisvert@intalio.com">Alex Boisvert</a>
* @author <a href="mailto:dranatunga@users.sourceforge.net">Dilum Ranatunga</a>
*/
public interface CachePolicy<K,V>
{
/**
* Place an object in the cache. If the cache does not currently contain
* an object for the key specified, this mapping is added. If an object
* currently exists under the specified key, the current object is
* replaced with the new object.
* <p>
* If the changes to the cache cause the eviction of any objects
* <strong>stored under other key(s)</strong>, events corresponding to
* the evictions are fired for each object. If an event listener is
* unable to handle the eviction, and throws a cache eviction exception,
* that exception is propagated to the caller. If such an exception is
* thrown, the cache itself should be left as it was before the
* <code>put()</code> operation was invoked: the the object whose
* eviction failed is still in the cache, and the new insertion or
* modification is reverted.
*
* @param key key for the cached object
* @param value the cached object
* @throws CacheEvictionException propagated if, while evicting objects
* to make room for new object, an eviction listener encountered
* this problem.
*/
public void put( K key, V value ) throws CacheEvictionException;
/**
* Obtain the object stored under the key specified.
*
* @param key key the object was cached under
* @return the object if it is still in the cache, null otherwise.
*/
public V get( K key );
/**
* Remove the object stored under the key specified. Note that since
* eviction notices are only fired when objects under <strong>different
* keys</strong> are evicted, no event is fired for any object stored
* under this key (see {@link #put(Object, Object) put( )}).
*
* @param key key the object was stored in the cache under.
*/
public void remove( K key );
/**
* Remove all objects from the cache. Consistent with
* {@link #remove(Object) remove( )}, no eviction notices are fired.
*/
public void removeAll();
/**
* Enumerate through the objects currently in the cache.
*/
public Enumeration<V> elements();
/**
* Add a listener to this cache policy.
* <p>
* If this cache policy already contains a listener that is equal to
* the one being added, this call has no effect.
*
* @param listener the (non-null) listener to add to this policy
* @throws IllegalArgumentException if listener is null.
*/
public void addListener( CachePolicyListener<V> listener ) throws IllegalArgumentException;
/**
* Remove a listener from this cache policy. The listener is found
* using object equality, not identity.
*
* @param listener the listener to remove from this policy
*/
public void removeListener( CachePolicyListener<V> listener );
}
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