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 * @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     * Constructor that uses an ArrayList internally.
080     */
081    public GrowthList() {
082        super(new ArrayList<>());
083    }
084
085    /**
086     * Constructor that uses an ArrayList internally.
087     *
088     * @param initialCapacity  the initial capacity of the ArrayList
089     * @throws IllegalArgumentException if initial capacity is invalid
090     */
091    public GrowthList(final int initialCapacity) {
092        super(new ArrayList<>(initialCapacity));
093    }
094
095    /**
096     * Constructor that wraps (not copies).
097     *
098     * @param list  the list to decorate, must not be null
099     * @throws NullPointerException if list is null
100     */
101    protected GrowthList(final List<E> list) {
102        super(list);
103    }
104
105    /**
106     * Decorate the add method to perform the growth behavior.
107     * <p>
108     * If the requested index is greater than the current size, the list will
109     * grow to the new size. Indices between the old size and the requested
110     * size will be filled with {@code null}.
111     * <p>
112     * If the index is less than the current size, the value will be added to
113     * the underlying list directly.
114     * If the index is less than zero, the underlying list is called, which
115     * will probably throw an IndexOutOfBoundsException.
116     *
117     * @param index  the index to add at
118     * @param element  the object to add at the specified index
119     * @throws UnsupportedOperationException if the underlying list doesn't implement set
120     * @throws ClassCastException if the underlying list rejects the element
121     * @throws IllegalArgumentException if the underlying list rejects the element
122     */
123    @Override
124    public void add(final int index, final E element) {
125        final int size = decorated().size();
126        if (index > size) {
127            decorated().addAll(Collections.<E>nCopies(index - size, null));
128        }
129        decorated().add(index, element);
130    }
131
132    /**
133     * Decorate the addAll method to perform the growth behavior.
134     * <p>
135     * If the requested index is greater than the current size, the list will
136     * grow to the new size. Indices between the old size and the requested
137     * size will be filled with {@code null}.
138     * <p>
139     * If the index is less than the current size, the values will be added to
140     * the underlying list directly.
141     * If the index is less than zero, the underlying list is called, which
142     * will probably throw an IndexOutOfBoundsException.
143     *
144     * @param index  the index to add at
145     * @param coll  the collection to add at the specified index
146     * @return true if the list changed
147     * @throws UnsupportedOperationException if the underlying list doesn't implement set
148     * @throws ClassCastException if the underlying list rejects the element
149     * @throws IllegalArgumentException if the underlying list rejects the element
150     */
151    @Override
152    public boolean addAll(final int index, final Collection<? extends E> coll) {
153        final int size = decorated().size();
154        boolean result = false;
155        if (index > size) {
156            decorated().addAll(Collections.<E>nCopies(index - size, null));
157            result = true;
158        }
159        return decorated().addAll(index, coll) || result;
160    }
161
162    /**
163     * Decorate the set method to perform the growth behavior.
164     * <p>
165     * If the requested index is greater than the current size, the list will
166     * grow to the new size. Indices between the old size and the requested
167     * size will be filled with {@code null}.
168     * <p>
169     * If the index is less than the current size, the value will be set onto
170     * the underlying list directly.
171     * If the index is less than zero, the underlying list is called, which
172     * will probably throw an IndexOutOfBoundsException.
173     *
174     * @param index  the index to set
175     * @param element  the object to set at the specified index
176     * @return the object previously at that index
177     * @throws UnsupportedOperationException if the underlying list doesn't implement set
178     * @throws ClassCastException if the underlying list rejects the element
179     * @throws IllegalArgumentException if the underlying list rejects the element
180     */
181    @Override
182    public E set(final int index, final E element) {
183        final int size = decorated().size();
184        if (index >= size) {
185            decorated().addAll(Collections.<E>nCopies(index - size + 1, null));
186        }
187        return decorated().set(index, element);
188    }
189
190}