001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.camel.util;
018
019 import java.util.ArrayList;
020 import java.util.List;
021 import java.util.Map;
022
023 /**
024 * A number of helper methods for working with collections
025 *
026 * @version $Revision: 1.1 $
027 */
028 public class CollectionHelper {
029
030 /**
031 * Utility classes should not have a public constructor.
032 */
033 private CollectionHelper() {
034 }
035
036 /**
037 * Sets the value of the entry in the map for the given key, though if the
038 * map already contains a value for the given key then the value is appended
039 * to a list of values.
040 *
041 * @param map the map to add the entry to
042 * @param key the key in the map
043 * @param value the value to put in the map
044 */
045 public static void appendValue(Map map, Object key, Object value) {
046
047 Object oldValue = map.get(key);
048 if (oldValue != null) {
049 List list;
050 if (oldValue instanceof List) {
051 list = (List)oldValue;
052 } else {
053 list = new ArrayList();
054 list.add(oldValue);
055 }
056 list.add(value);
057 } else {
058 map.put(key, value);
059 }
060 }
061 }