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 }