content: /**
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.activemq.memory;
  
  /**
   * Defines the interface used to cache messages.
   */
  public interface Cache {
  
      /**
       * Gets an object that was previously <code>put</code> into this object.
       *
       * @param key
       * @return null if the object was not previously put or if the object has
       *         expired out of the cache.
       */
      Object get(Object key);
  
      /**
       * Puts an object into the cache.
       *
       * @param key
       * @param value
       */
      Object put(Object key, Object value);
  
      /**
       * Removes an object from the cache.
       *
       * @param key
       * @return the object associated with the key if it was still in the cache.
       */
      Object remove(Object key);
  
      /**
       * Lets a cache know it will not be used any further and that it can release
       * acquired resources
       */
      void close();
  
      /**
       * How big is the cache right now?
       *
       * @return the size.
       */
      int size();
  
  }
  