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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *  http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing,
13   * software distributed under the License is distributed on an
14   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   * KIND, either express or implied.  See the License for the
16   * specific language governing permissions and limitations
17   * under the License.
18   */
19  package org.apache.directory.server.core.cursor;
20  
21  
22  /**
23   * An empty Cursor implementation.
24   *
25   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
26   * @version $Rev$, $Date$
27   */
28  public class EmptyCursor<E> extends AbstractCursor<E>
29  {
30      public boolean available()
31      {
32          return false;
33      }
34  
35      public void before( E element ) throws Exception
36      {
37          checkNotClosed( "before()" );
38      }
39  
40  
41      public void after( E element ) throws Exception
42      {
43          checkNotClosed( "after()" );
44      }
45  
46  
47      public void beforeFirst() throws Exception
48      {
49          checkNotClosed( "beforeFirst()" );
50      }
51  
52  
53      public void afterLast() throws Exception
54      {
55          checkNotClosed( "afterLast()" );
56      }
57  
58  
59      public boolean first() throws Exception
60      {
61          checkNotClosed( "first()" );
62          return false;
63      }
64  
65  
66      public boolean last() throws Exception
67      {
68          checkNotClosed( "last()" );
69          return false;
70      }
71  
72  
73      public boolean previous() throws Exception
74      {
75          checkNotClosed( "previous()" );
76          return false;
77      }
78  
79  
80      public boolean next() throws Exception
81      {
82          checkNotClosed( "next()" );
83          return false;
84      }
85  
86  
87      public E get() throws Exception
88      {
89          checkNotClosed( "get()" );
90          throw new InvalidCursorPositionException( "This cursor is empty and cannot return elements!" );
91      }
92  
93  
94      public boolean isElementReused()
95      {
96          return false;
97      }
98  }