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.collections.iterators;
018    
019    import java.util.ListIterator;
020    
021    import org.apache.commons.collections.Unmodifiable;
022    
023    /** 
024     * Decorates a list iterator such that it cannot be modified.
025     *
026     * @since Commons Collections 3.0
027     * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
028     * 
029     * @author Stephen Colebourne
030     */
031    public final class UnmodifiableListIterator implements ListIterator, Unmodifiable {
032    
033        /** The iterator being decorated */
034        private ListIterator iterator;
035    
036        //-----------------------------------------------------------------------
037        /**
038         * Decorates the specified iterator such that it cannot be modified.
039         *
040         * @param iterator  the iterator to decorate
041         * @throws IllegalArgumentException if the iterator is null
042         */
043        public static ListIterator decorate(ListIterator iterator) {
044            if (iterator == null) {
045                throw new IllegalArgumentException("ListIterator must not be null");
046            }
047            if (iterator instanceof Unmodifiable) {
048                return iterator;
049            }
050            return new UnmodifiableListIterator(iterator);
051        }
052        
053        //-----------------------------------------------------------------------
054        /**
055         * Constructor.
056         *
057         * @param iterator  the iterator to decorate
058         */
059        private UnmodifiableListIterator(ListIterator iterator) {
060            super();
061            this.iterator = iterator;
062        }
063    
064        //-----------------------------------------------------------------------
065        public boolean hasNext() {
066            return iterator.hasNext();
067        }
068    
069        public Object next() {
070            return iterator.next();
071        }
072    
073        public int nextIndex() {
074            return iterator.nextIndex();
075        }
076    
077        public boolean hasPrevious() {
078            return iterator.hasPrevious();
079        }
080    
081        public Object previous() {
082            return iterator.previous();
083        }
084    
085        public int previousIndex() {
086            return iterator.previousIndex();
087        }
088    
089        public void remove() {
090            throw new UnsupportedOperationException("remove() is not supported");
091        }
092    
093        public void set(Object obj) {
094            throw new UnsupportedOperationException("set() is not supported");
095        }
096    
097        public void add(Object obj) {
098            throw new UnsupportedOperationException("add() is not supported");
099        }
100    
101    }