Cache


1   /*
2    *  Licensed to the Apache Software Foundation (ASF) under one or more
3    *  contributor license agreements.  See the NOTICE file distributed with
4    *  this work for additional information regarding copyright ownership.
5    *  The ASF licenses this file to You under the Apache License, Version 2.0
6    *  (the "License"); you may not use this file except in compliance with
7    *  the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   *  Unless required by applicable law or agreed to in writing, software
12   *  distributed under the License is distributed on an "AS IS" BASIS,
13   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   *  See the License for the specific language governing permissions and
15   *  limitations under the License.
16   *
17   */
18  
19  package org.apache.tools.ant.types.selectors.modifiedselector;
20  
21  
22  import java.util.Iterator  ;
23  
24  
25  /**
26   * A Cache let the user store key-value-pairs in a permanent manner and access
27   * them.
28   * It is possible that a client uses get() before load() therefore the
29   * implementation must ensure that no error occurred because of the wrong
30   * <i>order</i>.
31   * The implementing class should implement a useful toString() method.
32   *
33   * @version 2003-09-13
34   * @since  Ant 1.6
35   */
36  public interface Cache {
37  
38      /**
39       * Checks its prerequisites.
40       * @return <i>true</i> if all is ok, otherwise <i>false</i>.
41       */
42      boolean isValid();
43  
44      /** Deletes the cache. If file based the file has to be deleted also. */
45      void delete();
46  
47      /** Loads the cache, must handle not existing cache. */
48      void load();
49  
50      /** Saves modification of the cache. */
51      void save();
52  
53      /**
54       * Returns a value for a given key from the cache.
55       * @param key the key
56       * @return the stored value
57       */
58      Object   get(Object   key);
59  
60      /**
61       * Saves a key-value-pair in the cache.
62       * @param key the key
63       * @param value the value
64       */
65      void put(Object   key, Object   value);
66  
67      /**
68       * Returns an iterator over the keys in the cache.
69       * @return An iterator over the keys.
70       */
71      Iterator   iterator();
72  }
73
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