    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 *      https://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    /**
    080     * Always throws {@link UnsupportedOperationException}.
    081     *
    082     * @param obj Ignored.
    083     * @throws UnsupportedOperationException Always thrown.
    084     */
    085    @Override
    086    public void add(final E obj) {
    087        throw new UnsupportedOperationException("add() is not supported");
    088    }
    089
    090    @Override
    091    public boolean hasNext() {
    092        return iterator.hasNext();
    093    }
    094
    095    @Override
    096    public boolean hasPrevious() {
    097        return iterator.hasPrevious();
    098    }
    099
    100    @Override
    101    public E next() {
    102        return iterator.next();
    103    }
    104
    105    @Override
    106    public int nextIndex() {
    107        return iterator.nextIndex();
    108    }
    109
    110    @Override
    111    public E previous() {
    112        return iterator.previous();
    113    }
    114
    115    @Override
    116    public int previousIndex() {
    117        return iterator.previousIndex();
    118    }
    119
    120    /**
    121     * Always throws {@link UnsupportedOperationException}.
    122     *
    123     * @throws UnsupportedOperationException Always thrown.
    124     */
    125    @Override
    126    public void remove() {
    127        throw new UnsupportedOperationException("remove() is not supported");
    128    }
    129
    130    /**
    131     * Always throws {@link UnsupportedOperationException}.
    132     *
    133     * @param ignored Ignored.
    134     * @throws UnsupportedOperationException Always thrown.
    135     */
    136    @Override
    137    public void set(final E ignored) {
    138        throw new UnsupportedOperationException("set() is not supported");
    139    }
    140
    141}