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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   *    https://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   */
20  
21  package org.apache.directory.api.util;
22  
23  
24  import java.util.HashMap;
25  
26  import org.apache.directory.api.i18n.I18n;
27  
28  
29  /**
30   * A Map implementation derived from HashMap that only overrides a single method
31   * put() in order to prevent duplicate keyed entries to be added.
32   * 
33   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
34   */
35  @SuppressWarnings("rawtypes")
36  public class NoDuplicateKeysMap extends HashMap
37  {
38      // add a serial version uid, so that if we change things in the future
39      // without changing the format, we can still deserialize properly.
40      private static final long serialVersionUID = 5107433500719957457L;
41  
42      /**
43       * Overrides java.util.Map.put(java.lang.Object, java.lang.Object) to
44       * prevent duplicate keys.
45       * 
46       * @see java.util.Map#put(java.lang.Object, java.lang.Object)
47       */
48      @SuppressWarnings("unchecked")
49      @Override
50      public Object put( Object key, Object value )
51      {
52          if ( containsKey( key ) )
53          {
54              throw new IllegalArgumentException( I18n.err( I18n.ERR_17034_ADDING_DUP_KEYS_NOT_ALLOWED ) );
55          }
56          else
57          {
58              return super.put( key, value );
59          }
60      }
61  }