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.lang.reflect.Array;
020    import java.util.ArrayList;
021    import java.util.Collection;
022    import java.util.List;
023    import java.util.Map;
024    
025    import org.w3c.dom.NodeList;
026    
027    /**
028     * A number of helper methods for working with collections
029     *
030     * @version $Revision: 1927 $
031     */
032    public final class CollectionHelper {
033    
034        /**
035         * Utility classes should not have a public constructor.
036         */
037        private CollectionHelper() {
038        }
039    
040        /**
041         * Returns the size of the collection if it can be determined to be a collection
042         *
043         * @param value the collection
044         * @return the size, or <tt>null</tt> if not a collection
045         */
046        public static Integer size(Object value) {
047            if (value != null) {
048                if (value instanceof Collection) {
049                    Collection collection = (Collection)value;
050                    return collection.size();
051                } else if (value instanceof Map) {
052                    Map map = (Map)value;
053                    return map.size();
054                } else if (value instanceof Object[]) {
055                    Object[] array = (Object[])value;
056                    return array.length;
057                } else if (value.getClass().isArray()) {
058                    return Array.getLength(value);
059                } else if (value instanceof NodeList) {
060                    NodeList nodeList = (NodeList)value;
061                    return nodeList.getLength();
062                }
063            }
064            return null;
065        }
066    
067        /**
068         * Sets the value of the entry in the map for the given key, though if the
069         * map already contains a value for the given key then the value is appended
070         * to a list of values.
071         *
072         * @param map the map to add the entry to
073         * @param key the key in the map
074         * @param value the value to put in the map
075         */
076        public static void appendValue(Map map, Object key, Object value) {
077            Object oldValue = map.get(key);
078            if (oldValue != null) {
079                List list;
080                if (oldValue instanceof List) {
081                    list = (List)oldValue;
082                } else {
083                    list = new ArrayList();
084                    list.add(oldValue);
085                }
086                list.add(value);
087            } else {
088                map.put(key, value);
089            }
090        }
091    
092        /**
093         * Filters the given list to skip instanceof filter objects.
094         * 
095         * @param list  the list
096         * @param filters  objects to skip
097         * @return a new list without the filtered objects
098         */
099        public static List filterList(List list, Object... filters) {
100            List answer = new ArrayList();
101            for (Object o : list) {
102                for (Object filter : filters) {
103                    if (!o.getClass().isInstance(filter)) {
104                        answer.add(o);
105                    }
106                }
107            }
108            return answer;
109        }
110    }