    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.list;
    018
    019import java.util.Collection;
    020import java.util.Iterator;
    021import java.util.List;
    022import java.util.ListIterator;
    023import java.util.function.Predicate;
    024
    025import org.apache.commons.collections4.Unmodifiable;
    026import org.apache.commons.collections4.iterators.UnmodifiableIterator;
    027import org.apache.commons.collections4.iterators.UnmodifiableListIterator;
    028
    029/**
    030 * Decorates another {@code List} to ensure it can't be altered.
    031 * <p>
    032 * This class is Serializable from Commons Collections 3.1.
    033 * </p>
    034 * <p>
    035 * Attempts to modify it will result in an UnsupportedOperationException.
    036 * </p>
    037 *
    038 * @param <E> the type of the elements in the list.
    039 * @since 3.0
    040 */
    041public final class UnmodifiableList<E>
    042        extends AbstractSerializableListDecorator<E>
    043        implements Unmodifiable {
    044
    045    /** Serialization version */
    046    private static final long serialVersionUID = 6595182819922443652L;
    047
    048    /**
    049     * Factory method to create an unmodifiable list.
    050     *
    051     * @param <E> the type of the elements in the list
    052     * @param list  the list to decorate, must not be null
    053     * @return a new unmodifiable list
    054     * @throws NullPointerException if list is null
    055     * @since 4.0
    056     */
    057    public static <E> List<E> unmodifiableList(final List<? extends E> list) {
    058        if (list instanceof Unmodifiable) {
    059            @SuppressWarnings("unchecked") // safe to upcast
    060            final List<E> tmpList = (List<E>) list;
    061            return tmpList;
    062        }
    063        return new UnmodifiableList<>(list);
    064    }
    065
    066    /**
    067     * Constructor that wraps (not copies).
    068     *
    069     * @param list  the list to decorate, must not be null
    070     * @throws NullPointerException if list is null
    071     */
    072    @SuppressWarnings("unchecked") // safe to upcast
    073    public UnmodifiableList(final List<? extends E> list) {
    074        super((List<E>) list);
    075    }
    076
    077    @Override
    078    public void add(final int index, final E object) {
    079        throw new UnsupportedOperationException();
    080    }
    081
    082    @Override
    083    public boolean add(final Object object) {
    084        throw new UnsupportedOperationException();
    085    }
    086
    087    @Override
    088    public boolean addAll(final Collection<? extends E> coll) {
    089        throw new UnsupportedOperationException();
    090    }
    091
    092    @Override
    093    public boolean addAll(final int index, final Collection<? extends E> coll) {
    094        throw new UnsupportedOperationException();
    095    }
    096
    097    @Override
    098    public void clear() {
    099        throw new UnsupportedOperationException();
    100    }
    101
    102    @Override
    103    public Iterator<E> iterator() {
    104        return UnmodifiableIterator.unmodifiableIterator(decorated().iterator());
    105    }
    106
    107    @Override
    108    public ListIterator<E> listIterator() {
    109        return UnmodifiableListIterator.unmodifiableListIterator(decorated().listIterator());
    110    }
    111
    112    @Override
    113    public ListIterator<E> listIterator(final int index) {
    114        return UnmodifiableListIterator.unmodifiableListIterator(decorated().listIterator(index));
    115    }
    116
    117    @Override
    118    public E remove(final int index) {
    119        throw new UnsupportedOperationException();
    120    }
    121
    122    @Override
    123    public boolean remove(final Object object) {
    124        throw new UnsupportedOperationException();
    125    }
    126
    127    @Override
    128    public boolean removeAll(final Collection<?> coll) {
    129        throw new UnsupportedOperationException();
    130    }
    131
    132    /**
    133     * @since 4.4
    134     */
    135    @Override
    136    public boolean removeIf(final Predicate<? super E> filter) {
    137        throw new UnsupportedOperationException();
    138    }
    139
    140    @Override
    141    public boolean retainAll(final Collection<?> coll) {
    142        throw new UnsupportedOperationException();
    143    }
    144
    145    @Override
    146    public E set(final int index, final E object) {
    147        throw new UnsupportedOperationException();
    148    }
    149
    150    @Override
    151    public List<E> subList(final int fromIndex, final int toIndex) {
    152        final List<E> sub = decorated().subList(fromIndex, toIndex);
    153        return new UnmodifiableList<>(sub);
    154    }
    155
    156}