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.Iterator;
020
021 import org.apache.commons.collections.Unmodifiable;
022
023 /**
024 * Decorates an 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 UnmodifiableIterator implements Iterator, Unmodifiable {
032
033 /** The iterator being decorated */
034 private Iterator iterator;
035
036 //-----------------------------------------------------------------------
037 /**
038 * Decorates the specified iterator such that it cannot be modified.
039 * <p>
040 * If the iterator is already unmodifiable it is returned directly.
041 *
042 * @param iterator the iterator to decorate
043 * @throws IllegalArgumentException if the iterator is null
044 */
045 public static Iterator decorate(Iterator iterator) {
046 if (iterator == null) {
047 throw new IllegalArgumentException("Iterator must not be null");
048 }
049 if (iterator instanceof Unmodifiable) {
050 return iterator;
051 }
052 return new UnmodifiableIterator(iterator);
053 }
054
055 //-----------------------------------------------------------------------
056 /**
057 * Constructor.
058 *
059 * @param iterator the iterator to decorate
060 */
061 private UnmodifiableIterator(Iterator iterator) {
062 super();
063 this.iterator = iterator;
064 }
065
066 //-----------------------------------------------------------------------
067 public boolean hasNext() {
068 return iterator.hasNext();
069 }
070
071 public Object next() {
072 return iterator.next();
073 }
074
075 public void remove() {
076 throw new UnsupportedOperationException("remove() is not supported");
077 }
078
079 }