CachePolicy


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22  package org.jboss.util;
23  
24  /**
25   * Interface that specifies a policy for caches. <p>
26   * Implementation classes can implement a LRU policy, a random one, 
27   * a MRU one, or any other suitable policy.
28   * 
29   * @author <a HREF="mailto:simone.bordet@compaq.com">Simone Bordet</a>
30   * @version $Revision: 1958 $
31   */
32  public interface CachePolicy
33  {
34     /**
35      * Returns the object paired with the specified key if it's 
36      * present in the cache, otherwise must return null. <br>
37      * Implementations of this method must have complexity of order O(1).
38      * Differently from {@link #peek} this method not only return whether
39      * the object is present in the cache or not, but also 
40      * applies the implemented policy that will "refresh" the cached 
41      * object in the cache, because this cached object
42      * was really requested.
43      * 
44      * @param key the key paired with the object
45      * @see #peek
46      */
47     Object   get(Object   key);
48  
49     /**
50      * Returns the object paired with the specified key if it's 
51      * present in the cache, otherwise must return null. <br>
52      * Implementations of this method must have complexity of order O(1).
53      * This method should not apply the implemented caching policy to the 
54      * object paired with the given key, so that a client can 
55      * query if an object is cached without "refresh" its cache status. Real 
56      * requests for the object must be done using {@link #get}.
57      * 
58      * @param key the key paired with the object
59      * @see #get
60      */  
61     Object   peek(Object   key);
62     
63     /**
64      * Inserts the specified object into the cache following the 
65      * implemented policy. <br>
66      * Implementations of this method must have complexity of order O(1).
67      * 
68      * @param key the key paired with the object
69      * @param object the object to cache
70      * @see #remove
71      */
72     void insert(Object   key, Object   object);
73     
74     /**
75      * Remove the cached object paired with the specified key. <br>
76      * Implementations of this method must have complexity of order O(1).
77      * 
78      * @param key the key paired with the object
79      * @see #insert
80      */
81     void remove(Object   key);
82     
83     /**
84      * Flushes the cached objects from the cache.
85      */
86     void flush();
87  
88     /**
89      * Get the size of the cache.
90      */
91     int size();
92  
93  
94  
95     /**
96      * create the service, do expensive operations etc 
97      */
98     void create() throws Exception  ;
99     
100    /**
101     * start the service, create is already called
102     */
103    void start() throws Exception  ;
104    
105    /**
106     * stop the service
107     */
108    void stop();
109    
110    /**
111     * destroy the service, tear down 
112     */
113    void destroy();
114 }
115
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