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