001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.activemq.memory;
018
019/**
020 * Defines the interface used to cache messages.
021 */
022public interface Cache {
023
024    /**
025     * Gets an object that was previously <code>put</code> into this object.
026     *
027     * @param key
028     * @return null if the object was not previously put or if the object has
029     *         expired out of the cache.
030     */
031    Object get(Object key);
032
033    /**
034     * Puts an object into the cache.
035     *
036     * @param key
037     * @param value
038     */
039    Object put(Object key, Object value);
040
041    /**
042     * Removes an object from the cache.
043     *
044     * @param key
045     * @return the object associated with the key if it was still in the cache.
046     */
047    Object remove(Object key);
048
049    /**
050     * Lets a cache know it will not be used any further and that it can release
051     * acquired resources
052     */
053    void close();
054
055    /**
056     * How big is the cache right now?
057     *
058     * @return the size.
059     */
060    int size();
061
062}