    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.BoundedCollection;
    026import org.apache.commons.collections4.iterators.AbstractListIteratorDecorator;
    027import org.apache.commons.collections4.iterators.UnmodifiableIterator;
    028
    029/**
    030 * Decorates another <code>List</code> 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    /** Serialization version */
    053    private static final long serialVersionUID = -2218010673611160319L;
    054
    055    /**
    056     * Factory method to create a fixed size list.
    057     *
    058     * @param <E> the type of the elements in the list
    059     * @param list  the list to decorate, must not be null
    060     * @return a new fixed size list
    061     * @throws NullPointerException if list is null
    062     * @since 4.0
    063     */
    064    public static <E> FixedSizeList<E> fixedSizeList(final List<E> list) {
    065        return new FixedSizeList<>(list);
    066    }
    067
    068    //-----------------------------------------------------------------------
    069    /**
    070     * Constructor that wraps (not copies).
    071     *
    072     * @param list  the list to decorate, must not be null
    073     * @throws NullPointerException if list is null
    074     */
    075    protected FixedSizeList(final List<E> list) {
    076        super(list);
    077    }
    078
    079    //-----------------------------------------------------------------------
    080    @Override
    081    public boolean add(final E object) {
    082        throw unsupportedOperationException();
    083    }
    084
    085    @Override
    086    public void add(final int index, final E object) {
    087        throw unsupportedOperationException();
    088    }
    089
    090    @Override
    091    public boolean addAll(final Collection<? extends E> coll) {
    092        throw unsupportedOperationException();
    093    }
    094
    095    @Override
    096    public boolean addAll(final int index, final Collection<? extends E> coll) {
    097        throw unsupportedOperationException();
    098    }
    099
    100    @Override
    101    public void clear() {
    102        throw unsupportedOperationException();
    103    }
    104
    105    @Override
    106    public E get(final int index) {
    107        return decorated().get(index);
    108    }
    109
    110    @Override
    111    public int indexOf(final Object object) {
    112        return decorated().indexOf(object);
    113    }
    114
    115    @Override
    116    public Iterator<E> iterator() {
    117        return UnmodifiableIterator.unmodifiableIterator(decorated().iterator());
    118    }
    119
    120    @Override
    121    public int lastIndexOf(final Object object) {
    122        return decorated().lastIndexOf(object);
    123    }
    124
    125    @Override
    126    public ListIterator<E> listIterator() {
    127        return new FixedSizeListIterator(decorated().listIterator(0));
    128    }
    129
    130    @Override
    131    public ListIterator<E> listIterator(final int index) {
    132        return new FixedSizeListIterator(decorated().listIterator(index));
    133    }
    134
    135    @Override
    136    public E remove(final int index) {
    137        throw unsupportedOperationException();
    138    }
    139
    140    @Override
    141    public boolean remove(final Object object) {
    142        throw unsupportedOperationException();
    143    }
    144
    145    /**
    146     * @since 4.4
    147     */
    148    @Override
    149    public boolean removeIf(Predicate<? super E> filter) {
    150        throw unsupportedOperationException();
    151    }
    152
    153    @Override
    154    public boolean removeAll(final Collection<?> coll) {
    155        throw unsupportedOperationException();
    156    }
    157
    158    @Override
    159    public boolean retainAll(final Collection<?> coll) {
    160        throw unsupportedOperationException();
    161    }
    162
    163    @Override
    164    public E set(final int index, final E object) {
    165        return decorated().set(index, object);
    166    }
    167
    168    @Override
    169    public List<E> subList(final int fromIndex, final int toIndex) {
    170        final List<E> sub = decorated().subList(fromIndex, toIndex);
    171        return new FixedSizeList<>(sub);
    172    }
    173
    174    /**
    175     * List iterator that only permits changes via set()
    176     */
    177    private class FixedSizeListIterator extends AbstractListIteratorDecorator<E> {
    178        protected FixedSizeListIterator(final ListIterator<E> iterator) {
    179            super(iterator);
    180        }
    181        @Override
    182        public void remove() {
    183            throw unsupportedOperationException();
    184        }
    185        @Override
    186        public void add(final Object object) {
    187            throw unsupportedOperationException();
    188        }
    189    }
    190
    191    @Override
    192    public boolean isFull() {
    193        return true;
    194    }
    195
    196    @Override
    197    public int maxSize() {
    198        return size();
    199    }
    200
    201    private static UnsupportedOperationException unsupportedOperationException() {
    202        return new UnsupportedOperationException("List is fixed size");
    203    }
    204
    205}