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}