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}