    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.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.BoundedCollection;
    026import org.apache.commons.collections4.iterators.AbstractListIteratorDecorator;
    027import org.apache.commons.collections4.iterators.UnmodifiableIterator;
    028
    029/**
    030 * Decorates another {@code List} to fix the size preventing add/remove.
    031 * <p>
    032 * The add, remove, clear and retain operations are unsupported.
    033 * The set method is allowed (as it doesn't change the list size).
    034 * </p>
    035 * <p>
    036 * NOTE:
    037 * Modifying the decorated list directly would results in influencing the outcome
    038 * of method calls on this object. For example, the bounds of this list would reflect
    039 * a newly added object to the underlying list.
    040 * </p>
    041 * <p>
    042 * This class is Serializable from Commons Collections 3.1.
    043 * </p>
    044 *
    045 * @param <E> The type of elements in this collection
    046 * @since 3.0
    047 */
    048public class FixedSizeList<E>
    049        extends AbstractSerializableListDecorator<E>
    050        implements BoundedCollection<E> {
    051
    052    /**
    053     * List iterator that only permits changes via set()
    054     */
    055    private final class FixedSizeListIterator extends AbstractListIteratorDecorator<E> {
    056        protected FixedSizeListIterator(final ListIterator<E> iterator) {
    057            super(iterator);
    058        }
    059        @Override
    060        public void add(final Object object) {
    061            throw unsupportedOperationException();
    062        }
    063        @Override
    064        public void remove() {
    065            throw unsupportedOperationException();
    066        }
    067    }
    068
    069    /** Serialization version */
    070    private static final long serialVersionUID = -2218010673611160319L;
    071
    072    /**
    073     * Factory method to create a fixed size list.
    074     *
    075     * @param <E> The type of the elements in the list
    076     * @param list  The list to decorate, must not be null
    077     * @return A new fixed size list
    078     * @throws NullPointerException if list is null
    079     * @since 4.0
    080     */
    081    public static <E> FixedSizeList<E> fixedSizeList(final List<E> list) {
    082        return new FixedSizeList<>(list);
    083    }
    084
    085    /**
    086     * Always throws {@link UnsupportedOperationException}.
    087     *
    088     * @throws UnsupportedOperationException Always thrown.
    089     */
    090    private static UnsupportedOperationException unsupportedOperationException() {
    091        return new UnsupportedOperationException("List is fixed size");
    092    }
    093
    094    /**
    095     * Constructor that wraps (not copies).
    096     *
    097     * @param list  The list to decorate, must not be null
    098     * @throws NullPointerException if list is null
    099     */
    100    protected FixedSizeList(final List<E> list) {
    101        super(list);
    102    }
    103
    104    @Override
    105    public boolean add(final E object) {
    106        throw unsupportedOperationException();
    107    }
    108
    109    @Override
    110    public void add(final int index, final E object) {
    111        throw unsupportedOperationException();
    112    }
    113
    114    @Override
    115    public boolean addAll(final Collection<? extends E> coll) {
    116        throw unsupportedOperationException();
    117    }
    118
    119    @Override
    120    public boolean addAll(final int index, final Collection<? extends E> coll) {
    121        throw unsupportedOperationException();
    122    }
    123
    124    @Override
    125    public void clear() {
    126        throw unsupportedOperationException();
    127    }
    128
    129    @Override
    130    public E get(final int index) {
    131        return decorated().get(index);
    132    }
    133
    134    @Override
    135    public int indexOf(final Object object) {
    136        return decorated().indexOf(object);
    137    }
    138
    139    @Override
    140    public boolean isFull() {
    141        return true;
    142    }
    143
    144    @Override
    145    public Iterator<E> iterator() {
    146        return UnmodifiableIterator.unmodifiableIterator(decorated().iterator());
    147    }
    148
    149    @Override
    150    public int lastIndexOf(final Object object) {
    151        return decorated().lastIndexOf(object);
    152    }
    153
    154    @Override
    155    public ListIterator<E> listIterator() {
    156        return new FixedSizeListIterator(decorated().listIterator(0));
    157    }
    158
    159    @Override
    160    public ListIterator<E> listIterator(final int index) {
    161        return new FixedSizeListIterator(decorated().listIterator(index));
    162    }
    163
    164    @Override
    165    public int maxSize() {
    166        return size();
    167    }
    168
    169    @Override
    170    public E remove(final int index) {
    171        throw unsupportedOperationException();
    172    }
    173
    174    @Override
    175    public boolean remove(final Object object) {
    176        throw unsupportedOperationException();
    177    }
    178
    179    @Override
    180    public boolean removeAll(final Collection<?> coll) {
    181        throw unsupportedOperationException();
    182    }
    183
    184    /**
    185     * @since 4.4
    186     */
    187    @Override
    188    public boolean removeIf(final Predicate<? super E> filter) {
    189        throw unsupportedOperationException();
    190    }
    191
    192    @Override
    193    public boolean retainAll(final Collection<?> coll) {
    194        throw unsupportedOperationException();
    195    }
    196
    197    @Override
    198    public E set(final int index, final E object) {
    199        return decorated().set(index, object);
    200    }
    201
    202    @Override
    203    public List<E> subList(final int fromIndex, final int toIndex) {
    204        final List<E> sub = decorated().subList(fromIndex, toIndex);
    205        return new FixedSizeList<>(sub);
    206    }
    207
    208}