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