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 }