Sequence


1   /*
2    * Copyright 2005 The Apache Software Foundation.
3    * 
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at 
7    * 
8    *     http://www.apache.org/licenses/LICENSE-2.0
9    * 
10   * Unless required by applicable law or agreed to in writing, software 
11   * distributed under the License is distributed on an "AS IS" BASIS, 
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
13   * See the License for the specific language governing permissions and 
14   * limitations under the License.
15   */
16  
17  /*
18   * Sequence.java
19   *
20   */
21   
22  package javax.jdo.datastore;
23  
24  
25  /**
26   *  Implementations of this interface can be used to obtain
27   *  sequences. The behavior with regard to the transaction and
28   *  rollover behavior are defined in the metadata.
29   *
30   *  @version 2.0
31   *  @since 2.0
32   */
33  public interface Sequence {
34  
35      /**
36       * Returns the fully qualified name of the <code>Sequence</code>.
37       * @return the name of the sequence
38       */
39      String   getName ();
40  
41      /**
42       * Returns the next sequence value as an Object. If the next
43       * sequence value is not available, throw JDODataStoreException.
44       * @return the next value
45       */
46      Object   next ();
47  
48      /**
49       * Provides a hint to the implementation that the application
50       * will need <code>additional</code> sequence value objects in
51       * short order. There is no externally visible behavior of this
52       * method. It is used to potentially improve the efficiency of
53       * the algorithm of obtaining additional sequence value objects.
54       * @param additional the number of additional values to allocate
55       */
56      void allocate (int additional);
57  
58      /**
59       * Returns the current sequence value object if it is
60       * available. It is intended to return a sequence value object
61       * previously used. If the current sequence value is not available,
62       * throw JDODataStoreException.
63       * @return the current value
64       */
65      Object   current ();
66      
67      /** 
68       * Returns the next sequence value as a long. If the next
69       * sequence value is not available or is not numeric, throw
70       * JDODataStoreException.
71       * @return the next value
72       */
73      long nextValue();
74      
75      /** 
76       * Returns the current sequence value as a long. If the current
77       * sequence value is not available or is not numeric, throw
78       * JDODataStoreException.
79       * @return the current value
80       */
81      long currentValue();
82  }
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