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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  package org.apache.portals.bridges.jsf;
18  
19  import java.util.Enumeration;
20  
21  /***
22   * <p>
23   * Enumeration without elements
24   * </p>
25   * <p>
26   * Code provided by MyFaces project.
27   * </p>
28   * 
29   * @author <a href="dlestrat@apache.org">David Le Strat </a>
30   */
31  public final class NullEnumeration implements Enumeration
32  {
33      /*** Null enumeration. */
34      private static final NullEnumeration nullEnumeration = new NullEnumeration();
35  
36      /***
37       * @return An instance of the enumeration.
38       */
39      public static final NullEnumeration instance()
40      {
41          return nullEnumeration;
42      }
43  
44      /***
45       * @see java.util.Enumeration#hasMoreElements()
46       */
47      public boolean hasMoreElements()
48      {
49          return false;
50      }
51  
52      /***
53       * @see java.util.Enumeration#nextElement()
54       */
55      public Object nextElement()
56      {
57          throw new UnsupportedOperationException("NullEnumeration has no elements");
58      }
59  }