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 }