    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 */
    030public final class UnmodifiableListIterator<E> implements ListIterator<E>, Unmodifiable {
    031
    032    /** The iterator being decorated */
    033    private final ListIterator<? extends E> iterator;
    034
    035    //-----------------------------------------------------------------------
    036    /**
    037     * Decorates the specified iterator such that it cannot be modified.
    038     *
    039     * @param <E>  the element type
    040     * @param iterator  the iterator to decorate
    041     * @return a new unmodifiable list iterator
    042     * @throws NullPointerException if the iterator is null
    043     */
    044    public static <E> ListIterator<E> umodifiableListIterator(final ListIterator<? extends E> iterator) {
    045        if (iterator == null) {
    046            throw new NullPointerException("ListIterator must not be null");
    047        }
    048        if (iterator instanceof Unmodifiable) {
    049            @SuppressWarnings("unchecked") // safe to upcast
    050            final ListIterator<E> tmpIterator = (ListIterator<E>) iterator;
    051            return tmpIterator;
    052        }
    053        return new UnmodifiableListIterator<>(iterator);
    054    }
    055
    056    //-----------------------------------------------------------------------
    057    /**
    058     * Constructor.
    059     *
    060     * @param iterator  the iterator to decorate
    061     */
    062    private UnmodifiableListIterator(final ListIterator<? extends E> iterator) {
    063        super();
    064        this.iterator = iterator;
    065    }
    066
    067    //-----------------------------------------------------------------------
    068    @Override
    069    public boolean hasNext() {
    070        return iterator.hasNext();
    071    }
    072
    073    @Override
    074    public E next() {
    075        return iterator.next();
    076    }
    077
    078    @Override
    079    public int nextIndex() {
    080        return iterator.nextIndex();
    081    }
    082
    083    @Override
    084    public boolean hasPrevious() {
    085        return iterator.hasPrevious();
    086    }
    087
    088    @Override
    089    public E previous() {
    090        return iterator.previous();
    091    }
    092
    093    @Override
    094    public int previousIndex() {
    095        return iterator.previousIndex();
    096    }
    097
    098    @Override
    099    public void remove() {
    100        throw new UnsupportedOperationException("remove() is not supported");
    101    }
    102
    103    @Override
    104    public void set(final E obj) {
    105        throw new UnsupportedOperationException("set() is not supported");
    106    }
    107
    108    @Override
    109    public void add(final E obj) {
    110        throw new UnsupportedOperationException("add() is not supported");
    111    }
    112
    113}