Cache


1   /*
2    * Copyright (C) The Apache Software Foundation. All rights reserved.
3    *
4    * This software is published under the terms of the Apache Software License
5    * version 1.1, a copy of which has been included  with this distribution in
6    * the LICENSE.txt file.
7    */
8   package org.apache.avalon.excalibur.cache;
9   
10  import org.apache.avalon.framework.component.Component;
11  
12  /**
13   * This is a cache that caches objects for reuse.
14   * Key is must not <code>null</code>. Value is possible to <code>null</code>.
15   *
16   * @author <a HREF="mailto:colus@apache.org">Eung-ju Park</a>
17   */
18  public interface Cache
19      extends Component
20  {
21      /**
22       * Add listener.
23       *
24       * @param listener listener instance to add
25       */
26      void addListener( CacheListener listener );
27  
28      /**
29       * Remove listener.
30       *
31       * @param listener listener instance to remove
32       */
33      void removeListener( CacheListener listener );
34  
35      /**
36       * Return capacity of cache.
37       *
38       * @return capacity of cache
39       */
40      int capacity();
41  
42      /**
43       * Return size of cache.
44       *
45       * @return the number of key-value mappings in this cache.
46       */
47      int size();
48  
49      /**
50       * Puts a new item in the cache. If the cache is full, remove the selected item.
51       *
52       * @param key key for the item
53       * @param value item
54       * @return old value. null if old value not exists.
55       */
56      Object   put( Object   key, Object   value );
57  
58      /**
59       * Get an item from the cache.
60       *
61       * @param key key to lookup the item
62       * @return the matching object in the cache. null if item not exists.
63       */
64      Object   get( Object   key );
65  
66      /**
67       * Removes an item from the cache.
68       *
69       * @param key key to remove
70       * @return the value removed. null if old value not exists.
71       */
72      Object   remove( Object   key );
73  
74      /**
75       * @param key
76       * @return true if matching item in the cache
77       */
78      boolean containsKey( Object   key );
79  
80      /**
81       * Clear cache.
82       */
83      void clear();
84  }
85
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