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} 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} 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} values, as
045 * {@code null} 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} grows on get. However, they
054 * can be used together by decorating twice.
055 * </p>
056 *
057 * @param <E> the type of the elements in the list.
058 * @see LazyList
059 * @since 3.2
060 */
061public class GrowthList<E> extends AbstractSerializableListDecorator<E> {
062
063    /** Serialization version */
064    private static final long serialVersionUID = -3620001881672L;
065
066    /**
067     * Factory method to create a growth list.
068     *
069     * @param <E> the type of the elements in the list
070     * @param list  the list to decorate, must not be null
071     * @return a new growth list
072     * @throws NullPointerException if list is null
073     * @since 4.0
074     */
075    public static <E> GrowthList<E> growthList(final List<E> list) {
076        return new GrowthList<>(list);
077    }
078
079    /**
080     * Constructor that uses an ArrayList internally.
081     */
082    public GrowthList() {
083        super(new ArrayList<>());
084    }
085
086    /**
087     * Constructor that uses an ArrayList internally.
088     *
089     * @param initialCapacity  the initial capacity of the ArrayList
090     * @throws IllegalArgumentException if initial capacity is invalid
091     */
092    public GrowthList(final int initialCapacity) {
093        super(new ArrayList<>(initialCapacity));
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     * Decorate the add method to perform the growth behavior.
108     * <p>
109     * If the requested index is greater than the current size, the list will
110     * grow to the new size. Indices between the old size and the requested
111     * size will be filled with {@code null}.
112     * <p>
113     * If the index is less than the current size, the value will be added to
114     * the underlying list directly.
115     * If the index is less than zero, the underlying list is called, which
116     * will probably throw an IndexOutOfBoundsException.
117     *
118     * @param index  the index to add at
119     * @param element  the object to add at the specified index
120     * @throws UnsupportedOperationException if the underlying list doesn't implement set
121     * @throws ClassCastException if the underlying list rejects the element
122     * @throws IllegalArgumentException if the underlying list rejects the element
123     */
124    @Override
125    public void add(final int index, final E element) {
126        final int size = decorated().size();
127        if (index > size) {
128            decorated().addAll(Collections.<E>nCopies(index - size, null));
129        }
130        decorated().add(index, element);
131    }
132
133    /**
134     * Decorate the addAll method to perform the growth behavior.
135     * <p>
136     * If the requested index is greater than the current size, the list will
137     * grow to the new size. Indices between the old size and the requested
138     * size will be filled with {@code null}.
139     * <p>
140     * If the index is less than the current size, the values will be added to
141     * the underlying list directly.
142     * If the index is less than zero, the underlying list is called, which
143     * will probably throw an IndexOutOfBoundsException.
144     *
145     * @param index  the index to add at
146     * @param coll  the collection to add at the specified index
147     * @return true if the list changed
148     * @throws UnsupportedOperationException if the underlying list doesn't implement set
149     * @throws ClassCastException if the underlying list rejects the element
150     * @throws IllegalArgumentException if the underlying list rejects the element
151     */
152    @Override
153    public boolean addAll(final int index, final Collection<? extends E> coll) {
154        final int size = decorated().size();
155        boolean result = false;
156        if (index > size) {
157            decorated().addAll(Collections.<E>nCopies(index - size, null));
158            result = true;
159        }
160        return decorated().addAll(index, coll) || result;
161    }
162
163    /**
164     * Decorate the set method to perform the growth behavior.
165     * <p>
166     * If the requested index is greater than the current size, the list will
167     * grow to the new size. Indices between the old size and the requested
168     * size will be filled with {@code null}.
169     * <p>
170     * If the index is less than the current size, the value will be set onto
171     * the underlying list directly.
172     * If the index is less than zero, the underlying list is called, which
173     * will probably throw an IndexOutOfBoundsException.
174     *
175     * @param index  the index to set
176     * @param element  the object to set at the specified index
177     * @return the object previously at that index
178     * @throws UnsupportedOperationException if the underlying list doesn't implement set
179     * @throws ClassCastException if the underlying list rejects the element
180     * @throws IllegalArgumentException if the underlying list rejects the element
181     */
182    @Override
183    public E set(final int index, final E element) {
184        final int size = decorated().size();
185        if (index >= size) {
186            decorated().addAll(Collections.<E>nCopies(index - size + 1, null));
187        }
188        return decorated().set(index, element);
189    }
190
191}