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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  
18  package org.apache.log4j.helpers;
19  
20  import java.util.Enumeration;
21  import java.util.NoSuchElementException;
22  
23  /**
24   * An always-empty Enumerator.
25   *
26   * @author Anders Kristensen
27   * @since version 1.0
28   */
29  @SuppressWarnings("rawtypes")
30  public class NullEnumeration implements Enumeration {
31    private static final NullEnumeration instance = new NullEnumeration();
32  
33    private NullEnumeration() {
34    }
35  
36    public static NullEnumeration getInstance() {
37      return instance;
38    }
39  
40    public boolean hasMoreElements() {
41      return false;
42    }
43  
44    public Object nextElement() {
45      throw new NoSuchElementException();
46    }
47  }