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 */ 017package org.apache.commons.collections4.iterators; 018 019import java.util.ListIterator; 020import java.util.Objects; 021 022import org.apache.commons.collections4.Unmodifiable; 023 024/** 025 * Decorates a list iterator such that it cannot be modified. 026 * <p> 027 * Attempts to modify it will result in an UnsupportedOperationException. 028 * </p> 029 * 030 * @param <E> the type of elements returned by this iterator. 031 * @since 3.0 032 */ 033public final class UnmodifiableListIterator<E> implements ListIterator<E>, Unmodifiable { 034 035 /** 036 * Decorates the specified iterator such that it cannot be modified. 037 * 038 * @param <E> the element type 039 * @param iterator the iterator to decorate 040 * @return a new unmodifiable list iterator 041 * @throws NullPointerException if the iterator is null 042 * @deprecated method name has typo in it. Use {@link org.apache.commons.collections4.iterators.UnmodifiableListIterator#unmodifiableListIterator(ListIterator)} instead. 043 */ 044 @Deprecated 045 public static <E> ListIterator<E> umodifiableListIterator(final ListIterator<? extends E> iterator) { 046 return unmodifiableListIterator(iterator); 047 } 048 049 /** 050 * Decorates the specified iterator such that it cannot be modified. 051 * 052 * @param <E> the element type 053 * @param iterator the iterator to decorate 054 * @return a new unmodifiable list iterator 055 * @throws NullPointerException if the iterator is null 056 */ 057 public static <E> ListIterator<E> unmodifiableListIterator(final ListIterator<? extends E> iterator) { 058 Objects.requireNonNull(iterator, "iterator"); 059 if (iterator instanceof Unmodifiable) { 060 @SuppressWarnings("unchecked") // safe to upcast 061 final ListIterator<E> tmpIterator = (ListIterator<E>) iterator; 062 return tmpIterator; 063 } 064 return new UnmodifiableListIterator<>(iterator); 065 } 066 067 /** The iterator being decorated */ 068 private final ListIterator<? extends E> iterator; 069 070 /** 071 * Constructs a new instance. 072 * 073 * @param iterator the iterator to decorate 074 */ 075 private UnmodifiableListIterator(final ListIterator<? extends E> iterator) { 076 this.iterator = iterator; 077 } 078 079 @Override 080 public void add(final E obj) { 081 throw new UnsupportedOperationException("add() is not supported"); 082 } 083 084 @Override 085 public boolean hasNext() { 086 return iterator.hasNext(); 087 } 088 089 @Override 090 public boolean hasPrevious() { 091 return iterator.hasPrevious(); 092 } 093 094 @Override 095 public E next() { 096 return iterator.next(); 097 } 098 099 @Override 100 public int nextIndex() { 101 return iterator.nextIndex(); 102 } 103 104 @Override 105 public E previous() { 106 return iterator.previous(); 107 } 108 109 @Override 110 public int previousIndex() { 111 return iterator.previousIndex(); 112 } 113 114 @Override 115 public void remove() { 116 throw new UnsupportedOperationException("remove() is not supported"); 117 } 118 119 @Override 120 public void set(final E obj) { 121 throw new UnsupportedOperationException("set() is not supported"); 122 } 123 124}