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