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;
020
021import org.apache.commons.collections4.Unmodifiable;
022
023/**
024 * Decorates a list iterator such that it cannot be modified.
025 * <p>
026 * Attempts to modify it will result in an UnsupportedOperationException.
027 *
028 * @since 3.0
029 * @version $Id: UnmodifiableListIterator.html 972421 2015-11-14 20:00:04Z tn $
030 */
031public final class UnmodifiableListIterator<E> implements ListIterator<E>, Unmodifiable {
032
033    /** The iterator being decorated */
034    private final ListIterator<? extends E> iterator;
035
036    //-----------------------------------------------------------------------
037    /**
038     * Decorates the specified iterator such that it cannot be modified.
039     *
040     * @param <E>  the element type
041     * @param iterator  the iterator to decorate
042     * @return a new unmodifiable list iterator
043     * @throws IllegalArgumentException if the iterator is null
044     */
045    public static <E> ListIterator<E> umodifiableListIterator(final ListIterator<? extends E> iterator) {
046        if (iterator == null) {
047            throw new IllegalArgumentException("ListIterator must not be null");
048        }
049        if (iterator instanceof Unmodifiable) {
050            @SuppressWarnings("unchecked") // safe to upcast
051            final ListIterator<E> tmpIterator = (ListIterator<E>) iterator;
052            return tmpIterator;
053        }
054        return new UnmodifiableListIterator<E>(iterator);
055    }
056
057    //-----------------------------------------------------------------------
058    /**
059     * Constructor.
060     *
061     * @param iterator  the iterator to decorate
062     */
063    private UnmodifiableListIterator(final ListIterator<? extends E> iterator) {
064        super();
065        this.iterator = iterator;
066    }
067
068    //-----------------------------------------------------------------------
069    public boolean hasNext() {
070        return iterator.hasNext();
071    }
072
073    public E next() {
074        return iterator.next();
075    }
076
077    public int nextIndex() {
078        return iterator.nextIndex();
079    }
080
081    public boolean hasPrevious() {
082        return iterator.hasPrevious();
083    }
084
085    public E previous() {
086        return iterator.previous();
087    }
088
089    public int previousIndex() {
090        return iterator.previousIndex();
091    }
092
093    public void remove() {
094        throw new UnsupportedOperationException("remove() is not supported");
095    }
096
097    public void set(final E obj) {
098        throw new UnsupportedOperationException("set() is not supported");
099    }
100
101    public void add(final E obj) {
102        throw new UnsupportedOperationException("add() is not supported");
103    }
104
105}