001/*
002 *  Licensed to the Apache Software Foundation (ASF) under one
003 *  or more contributor license agreements.  See the NOTICE file
004 *  distributed with this work for additional information
005 *  regarding copyright ownership.  The ASF licenses this file
006 *  to you under the Apache License, Version 2.0 (the
007 *  "License"); you may not use this file except in compliance
008 *  with the License.  You may obtain a copy of the License at
009 *  
010 *    http://www.apache.org/licenses/LICENSE-2.0
011 *  
012 *  Unless required by applicable law or agreed to in writing,
013 *  software distributed under the License is distributed on an
014 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 *  KIND, either express or implied.  See the License for the
016 *  specific language governing permissions and limitations
017 *  under the License. 
018 *  
019 */
020
021package org.apache.directory.api.util;
022
023
024import java.util.HashMap;
025
026import org.apache.directory.api.i18n.I18n;
027
028
029/**
030 * A Map implementation derived from HashMap that only overrides a single method
031 * put() in order to prevent duplicate keyed entries to be added.
032 * 
033 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
034 */
035@SuppressWarnings("rawtypes")
036public class NoDuplicateKeysMap extends HashMap
037{
038    /**
039     * Overrides java.util.Map.put(java.lang.Object, java.lang.Object) to
040     * prevent duplicate keys.
041     * 
042     * @see java.util.Map#put(java.lang.Object, java.lang.Object)
043     */
044    @SuppressWarnings("unchecked")
045    public Object put( Object key, Object value )
046    {
047        if ( containsKey( key ) )
048        {
049            throw new IllegalArgumentException( I18n.err( I18n.ERR_04422 ) );
050        }
051        else
052        {
053            return super.put( key, value );
054        }
055    }
056
057    // add a serial version uid, so that if we change things in the future
058    // without changing the format, we can still deserialize properly.
059    private static final long serialVersionUID = 5107433500719957457L;
060}