    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.ArrayList;
    020import java.util.Collection;
    021import java.util.Collections;
    022import java.util.List;
    023
    024/**
    025 * Decorates another <code>List</code> to make it seamlessly grow when
    026 * indices larger than the list size are used on add and set,
    027 * avoiding most IndexOutOfBoundsExceptions.
    028 * <p>
    029 * This class avoids errors by growing when a set or add method would
    030 * normally throw an IndexOutOfBoundsException.
    031 * Note that IndexOutOfBoundsException IS returned for invalid negative indices.
    032 * </p>
    033 * <p>
    034 * Trying to set or add to an index larger than the size will cause the list
    035 * to grow (using <code>null</code> elements). Clearly, care must be taken
    036 * not to use excessively large indices, as the internal list will grow to
    037 * match.
    038 * </p>
    039 * <p>
    040 * Trying to use any method other than add or set with an invalid index will
    041 * call the underlying list and probably result in an IndexOutOfBoundsException.
    042 * </p>
    043 * <p>
    044 * Take care when using this list with <code>null</code> values, as
    045 * <code>null</code> is the value added when growing the list.
    046 * </p>
    047 * <p>
    048 * All sub-lists will access the underlying list directly, and will throw
    049 * IndexOutOfBoundsExceptions.
    050 * </p>
    051 * <p>
    052 * This class differs from {@link LazyList} because here growth occurs on
    053 * set and add, where <code>LazyList</code> grows on get. However, they
    054 * can be used together by decorating twice.
    055 * </p>
    056 *
    057 * @see LazyList
    058 * @since 3.2
    059 */
    060public class GrowthList<E> extends AbstractSerializableListDecorator<E> {
    061
    062    /** Serialization version */
    063    private static final long serialVersionUID = -3620001881672L;
    064
    065    /**
    066     * Factory method to create a growth list.
    067     *
    068     * @param <E> the type of the elements in the list
    069     * @param list  the list to decorate, must not be null
    070     * @return a new growth list
    071     * @throws NullPointerException if list is null
    072     * @since 4.0
    073     */
    074    public static <E> GrowthList<E> growthList(final List<E> list) {
    075        return new GrowthList<>(list);
    076    }
    077
    078    //-----------------------------------------------------------------------
    079    /**
    080     * Constructor that uses an ArrayList internally.
    081     */
    082    public GrowthList() {
    083        super(new ArrayList<E>());
    084    }
    085
    086    /**
    087     * Constructor that uses an ArrayList internally.
    088     *
    089     * @param initialSize  the initial size of the ArrayList
    090     * @throws IllegalArgumentException if initial size is invalid
    091     */
    092    public GrowthList(final int initialSize) {
    093        super(new ArrayList<E>(initialSize));
    094    }
    095
    096    /**
    097     * Constructor that wraps (not copies).
    098     *
    099     * @param list  the list to decorate, must not be null
    100     * @throws NullPointerException if list is null
    101     */
    102    protected GrowthList(final List<E> list) {
    103        super(list);
    104    }
    105
    106    //-----------------------------------------------------------------------
    107    /**
    108     * Decorate the add method to perform the growth behaviour.
    109     * <p>
    110     * If the requested index is greater than the current size, the list will
    111     * grow to the new size. Indices between the old size and the requested
    112     * size will be filled with <code>null</code>.
    113     * <p>
    114     * If the index is less than the current size, the value will be added to
    115     * the underlying list directly.
    116     * If the index is less than zero, the underlying list is called, which
    117     * will probably throw an IndexOutOfBoundsException.
    118     *
    119     * @param index  the index to add at
    120     * @param element  the object to add at the specified index
    121     * @throws UnsupportedOperationException if the underlying list doesn't implement set
    122     * @throws ClassCastException if the underlying list rejects the element
    123     * @throws IllegalArgumentException if the underlying list rejects the element
    124     */
    125    @Override
    126    public void add(final int index, final E element) {
    127        final int size = decorated().size();
    128        if (index > size) {
    129            decorated().addAll(Collections.<E>nCopies(index - size, null));
    130        }
    131        decorated().add(index, element);
    132    }
    133
    134    //-----------------------------------------------------------------------
    135    /**
    136     * Decorate the addAll method to perform the growth behaviour.
    137     * <p>
    138     * If the requested index is greater than the current size, the list will
    139     * grow to the new size. Indices between the old size and the requested
    140     * size will be filled with <code>null</code>.
    141     * <p>
    142     * If the index is less than the current size, the values will be added to
    143     * the underlying list directly.
    144     * If the index is less than zero, the underlying list is called, which
    145     * will probably throw an IndexOutOfBoundsException.
    146     *
    147     * @param index  the index to add at
    148     * @param coll  the collection to add at the specified index
    149     * @return true if the list changed
    150     * @throws UnsupportedOperationException if the underlying list doesn't implement set
    151     * @throws ClassCastException if the underlying list rejects the element
    152     * @throws IllegalArgumentException if the underlying list rejects the element
    153     */
    154    @Override
    155    public boolean addAll(final int index, final Collection<? extends E> coll) {
    156        final int size = decorated().size();
    157        boolean result = false;
    158        if (index > size) {
    159            decorated().addAll(Collections.<E>nCopies(index - size, null));
    160            result = true;
    161        }
    162        return decorated().addAll(index, coll) || result;
    163    }
    164
    165    //-----------------------------------------------------------------------
    166    /**
    167     * Decorate the set method to perform the growth behaviour.
    168     * <p>
    169     * If the requested index is greater than the current size, the list will
    170     * grow to the new size. Indices between the old size and the requested
    171     * size will be filled with <code>null</code>.
    172     * <p>
    173     * If the index is less than the current size, the value will be set onto
    174     * the underlying list directly.
    175     * If the index is less than zero, the underlying list is called, which
    176     * will probably throw an IndexOutOfBoundsException.
    177     *
    178     * @param index  the index to set
    179     * @param element  the object to set at the specified index
    180     * @return the object previously at that index
    181     * @throws UnsupportedOperationException if the underlying list doesn't implement set
    182     * @throws ClassCastException if the underlying list rejects the element
    183     * @throws IllegalArgumentException if the underlying list rejects the element
    184     */
    185    @Override
    186    public E set(final int index, final E element) {
    187        final int size = decorated().size();
    188        if (index >= size) {
    189            decorated().addAll(Collections.<E>nCopies(index - size + 1, null));
    190        }
    191        return decorated().set(index, element);
    192    }
    193
    194}