    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.commons.jxpath;
    018
    019    import java.util.ArrayList;
    020    import java.util.Collections;
    021    import java.util.List;
    022
    023    /**
    024     * A simple implementation of {@link NodeSet} that behaves as a collection
    025     * of pointers.
    026     *
    027     * @author Dmitri Plotnikov
    028     * @version $Revision: 652845 $ $Date: 2008-05-02 12:46:46 -0500 (Fri, 02 May 2008) $
    029     */
    030    public class BasicNodeSet implements NodeSet {
    031        private List pointers = new ArrayList();
    032        private List readOnlyPointers;
    033        private List nodes;
    034        private List values;
    035
    036        /**
    037         * Add a pointer to this NodeSet.
    038         * @param pointer to add
    039         */
    040        public void add(Pointer pointer) {
    041            if (pointers.add(pointer)) {
    042                clearCacheLists();
    043            }
    044        }
    045
    046        /**
    047         * Add the specified NodeSet to this NodeSet.
    048         * @param nodeSet to add
    049         */
    050        public void add(NodeSet nodeSet) {
    051            if (pointers.addAll(nodeSet.getPointers())) {
    052                clearCacheLists();
    053            }
    054        }
    055
    056        /**
    057         * Remove a pointer from this NodeSet.
    058         * @param pointer to remove
    059         */
    060        public void remove(Pointer pointer) {
    061            if (pointers.remove(pointer)) {
    062                clearCacheLists();
    063            }
    064        }
    065
    066        public synchronized List getPointers() {
    067            if (readOnlyPointers == null) {
    068                readOnlyPointers = Collections.unmodifiableList(pointers);
    069            }
    070            return readOnlyPointers;
    071        }
    072
    073        public synchronized List getNodes() {
    074            if (nodes == null) {
    075                nodes = new ArrayList();
    076                for (int i = 0; i < pointers.size(); i++) {
    077                    Pointer pointer = (Pointer) pointers.get(i);
    078                    nodes.add(pointer.getNode());
    079                }
    080                nodes = Collections.unmodifiableList(nodes);
    081            }
    082            return nodes;
    083        }
    084
    085        public synchronized List getValues() {
    086            if (values == null) {
    087                values = new ArrayList();
    088                for (int i = 0; i < pointers.size(); i++) {
    089                    Pointer pointer = (Pointer) pointers.get(i);
    090                    values.add(pointer.getValue());
    091                }
    092                values = Collections.unmodifiableList(values);
    093            }
    094            return values;
    095        }
    096
    097        public String toString() {
    098            return pointers.toString();
    099        }
    100
    101        /**
    102         * Clear cache list members.
    103         */
    104        private synchronized void clearCacheLists() {
    105            readOnlyPointers = null;
    106            nodes = null;
    107            values = null;
    108        }
    109
    110    }