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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  }