1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.collections.list;
18
19 import java.util.ArrayList;
20 import java.util.Collection;
21 import java.util.Collections;
22 import java.util.List;
23
24 /**
25 * Decorates another <code>List</code> to make it seamlessly grow when
26 * indices larger than the list size are used on add and set,
27 * avoiding most IndexOutOfBoundsExceptions.
28 * <p>
29 * This class avoids errors by growing when a set or add method would
30 * normally throw an IndexOutOfBoundsException.
31 * Note that IndexOutOfBoundsException IS returned for invalid negative indices.
32 * <p>
33 * Trying to set or add to an index larger than the size will cause the list
34 * to grow (using <code>null</code> elements). Clearly, care must be taken
35 * not to use excessively large indices, as the internal list will grow to
36 * match.
37 * <p>
38 * Trying to use any method other than add or set with an invalid index will
39 * call the underlying list and probably result in an IndexOutOfBoundsException.
40 * <p>
41 * Take care when using this list with <code>null</code> values, as
42 * <code>null</code> is the value added when growing the list.
43 * <p>
44 * All sub-lists will access the underlying list directly, and will throw
45 * IndexOutOfBoundsExceptions.
46 * <p>
47 * This class differs from {@link LazyList} because here growth occurs on
48 * set and add, where <code>LazyList</code> grows on get. However, they
49 * can be used together by decorating twice.
50 *
51 * @see LazyList
52 * @since 3.2
53 * @version $Id: GrowthList.java 1429905 2013-01-07 17:15:14Z ggregory $
54 */
55 public class GrowthList<E> extends AbstractSerializableListDecorator<E> {
56
57 /** Serialization version */
58 private static final long serialVersionUID = -3620001881672L;
59
60 /**
61 * Factory method to create a growth list.
62 *
63 * @param <E> the type of the elements in the list
64 * @param list the list to decorate, must not be null
65 * @return a new growth list
66 * @throws IllegalArgumentException if list is null
67 */
68 public static <E> GrowthList<E> growthList(final List<E> list) {
69 return new GrowthList<E>(list);
70 }
71
72 //-----------------------------------------------------------------------
73 /**
74 * Constructor that uses an ArrayList internally.
75 */
76 public GrowthList() {
77 super(new ArrayList<E>());
78 }
79
80 /**
81 * Constructor that uses an ArrayList internally.
82 *
83 * @param initialSize the initial size of the ArrayList
84 * @throws IllegalArgumentException if initial size is invalid
85 */
86 public GrowthList(final int initialSize) {
87 super(new ArrayList<E>(initialSize));
88 }
89
90 /**
91 * Constructor that wraps (not copies).
92 *
93 * @param list the list to decorate, must not be null
94 * @throws IllegalArgumentException if list is null
95 */
96 protected GrowthList(final List<E> list) {
97 super(list);
98 }
99
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 }