1 /*
2 * Copyright (c) 2007, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package sun.awt.util;
27
28 import java.util.AbstractList;
29 import java.util.Arrays;
30 import java.util.Collection;
31 import java.util.ConcurrentModificationException;
32 import java.util.List;
33 import java.util.RandomAccess;
34
35 /**
36 * Resizable-array implementation of the <tt>List</tt> interface. Implements
37 * all optional list operations, and permits all elements, including
38 * <tt>null</tt>. In addition to implementing the <tt>List</tt> interface,
39 * this class provides methods to manipulate the size of the array that is
40 * used internally to store the list. (This class is roughly equivalent to
41 * <tt>Vector</tt>, except that it is unsynchronized.)<p>
42 *
43 * The <tt>size</tt>, <tt>isEmpty</tt>, <tt>get</tt>, <tt>set</tt>,
44 * <tt>iterator</tt>, and <tt>listIterator</tt> operations run in constant
45 * time. The <tt>add</tt> operation runs in <i>amortized constant time</i>,
46 * that is, adding n elements requires O(n) time. All of the other operations
47 * run in linear time (roughly speaking). The constant factor is low compared
48 * to that for the <tt>LinkedList</tt> implementation.<p>
49 *
50 * Each <tt>IdentityArrayList</tt> instance has a <i>capacity</i>. The capacity is
51 * the size of the array used to store the elements in the list. It is always
52 * at least as large as the list size. As elements are added to an IdentityArrayList,
53 * its capacity grows automatically. The details of the growth policy are not
54 * specified beyond the fact that adding an element has constant amortized
55 * time cost.<p>
56 *
57 * An application can increase the capacity of an <tt>IdentityArrayList</tt> instance
58 * before adding a large number of elements using the <tt>ensureCapacity</tt>
59 * operation. This may reduce the amount of incremental reallocation.
60 *
61 * <p><strong>Note that this implementation is not synchronized.</strong>
62 * If multiple threads access an <tt>IdentityArrayList</tt> instance concurrently,
63 * and at least one of the threads modifies the list structurally, it
64 * <i>must</i> be synchronized externally. (A structural modification is
65 * any operation that adds or deletes one or more elements, or explicitly
66 * resizes the backing array; merely setting the value of an element is not
67 * a structural modification.) This is typically accomplished by
68 * synchronizing on some object that naturally encapsulates the list.
69 *
70 * If no such object exists, the list should be "wrapped" using the
71 * {@link java.util.Collections#synchronizedList Collections.synchronizedList}
72 * method. This is best done at creation time, to prevent accidental
73 * unsynchronized access to the list:<pre>
74 * List list = Collections.synchronizedList(new IdentityArrayList(...));</pre>
75 *
76 * <p>The iterators returned by this class's <tt>iterator</tt> and
77 * <tt>listIterator</tt> methods are <i>fail-fast</i>: if the list is
78 * structurally modified at any time after the iterator is created, in any way
79 * except through the iterator's own <tt>remove</tt> or <tt>add</tt> methods,
80 * the iterator will throw a {@link ConcurrentModificationException}. Thus, in
81 * the face of concurrent modification, the iterator fails quickly and cleanly,
82 * rather than risking arbitrary, non-deterministic behavior at an undetermined
83 * time in the future.<p>
84 *
85 * Note that the fail-fast behavior of an iterator cannot be guaranteed
86 * as it is, generally speaking, impossible to make any hard guarantees in the
87 * presence of unsynchronized concurrent modification. Fail-fast iterators
88 * throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
89 * Therefore, it would be wrong to write a program that depended on this
90 * exception for its correctness: <i>the fail-fast behavior of iterators
91 * should be used only to detect bugs.</i><p>
92 *
93 */
94
95 public class IdentityArrayList<E> extends AbstractList<E>
96 implements List<E>, RandomAccess
97 {
98
99 /**
100 * The array buffer into which the elements of the IdentityArrayList are stored.
101 * The capacity of the IdentityArrayList is the length of this array buffer.
102 */
103 private transient Object[] elementData;
104
105 /**
106 * The size of the IdentityArrayList (the number of elements it contains).
107 *
108 * @serial
109 */
110 private int size;
111
112 /**
113 * Constructs an empty list with the specified initial capacity.
114 *
115 * @param initialCapacity the initial capacity of the list
116 * @exception IllegalArgumentException if the specified initial capacity
117 * is negative
118 */
119 public IdentityArrayList(int initialCapacity) {
120 super();
121 if (initialCapacity < 0)
122 throw new IllegalArgumentException("Illegal Capacity: "+
123 initialCapacity);
124 this.elementData = new Object[initialCapacity];
125 }
126
127 /**
128 * Constructs an empty list with an initial capacity of ten.
129 */
130 public IdentityArrayList() {
131 this(10);
132 }
133
134 /**
135 * Constructs a list containing the elements of the specified
136 * collection, in the order they are returned by the collection's
137 * iterator.
138 *
139 * @param c the collection whose elements are to be placed into this list
140 * @throws NullPointerException if the specified collection is null
141 */
142 public IdentityArrayList(Collection<? extends E> c) {
143 elementData = c.toArray();
144 size = elementData.length;
145 // defend against c.toArray (incorrectly) not returning Object[]
146 // (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652)
147 if (elementData.getClass() != Object[].class)
148 elementData = Arrays.copyOf(elementData, size, Object[].class);
149 }
150
151 /**
152 * Trims the capacity of this <tt>IdentityArrayList</tt> instance to be the
153 * list's current size. An application can use this operation to minimize
154 * the storage of an <tt>IdentityArrayList</tt> instance.
155 */
156 public void trimToSize() {
157 modCount++;
158 int oldCapacity = elementData.length;
159 if (size < oldCapacity) {
160 elementData = Arrays.copyOf(elementData, size);
161 }
162 }
163
164 /**
165 * Increases the capacity of this <tt>IdentityArrayList</tt> instance, if
166 * necessary, to ensure that it can hold at least the number of elements
167 * specified by the minimum capacity argument.
168 *
169 * @param minCapacity the desired minimum capacity
170 */
171 public void ensureCapacity(int minCapacity) {
172 modCount++;
173 int oldCapacity = elementData.length;
174 if (minCapacity > oldCapacity) {
175 Object oldData[] = elementData;
176 int newCapacity = (oldCapacity * 3)/2 + 1;
177 if (newCapacity < minCapacity)
178 newCapacity = minCapacity;
179 // minCapacity is usually close to size, so this is a win:
180 elementData = Arrays.copyOf(elementData, newCapacity);
181 }
182 }
183
184 /**
185 * Returns the number of elements in this list.
186 *
187 * @return the number of elements in this list
188 */
189 public int size() {
190 return size;
191 }
192
193 /**
194 * Returns <tt>true</tt> if this list contains no elements.
195 *
196 * @return <tt>true</tt> if this list contains no elements
197 */
198 public boolean isEmpty() {
199 return size == 0;
200 }
201
202 /**
203 * Returns <tt>true</tt> if this list contains the specified element.
204 * More formally, returns <tt>true</tt> if and only if this list contains
205 * at least one element <tt>e</tt> such that
206 * <tt>(o==null ? e==null : o == e)</tt>.
207 *
208 * @param o element whose presence in this list is to be tested
209 * @return <tt>true</tt> if this list contains the specified element
210 */
211 public boolean contains(Object o) {
212 return indexOf(o) >= 0;
213 }
214
215 /**
216 * Returns the index of the first occurrence of the specified element
217 * in this list, or -1 if this list does not contain the element.
218 * More formally, returns the lowest index <tt>i</tt> such that
219 * <tt>(o==null ? get(i)==null : o == get(i))</tt>,
220 * or -1 if there is no such index.
221 */
222 public int indexOf(Object o) {
223 for (int i = 0; i < size; i++) {
224 if (o == elementData[i]) {
225 return i;
226 }
227 }
228 return -1;
229 }
230
231 /**
232 * Returns the index of the last occurrence of the specified element
233 * in this list, or -1 if this list does not contain the element.
234 * More formally, returns the highest index <tt>i</tt> such that
235 * <tt>(o==null ? get(i)==null : o == get(i))</tt>,
236 * or -1 if there is no such index.
237 */
238 public int lastIndexOf(Object o) {
239 for (int i = size-1; i >= 0; i--) {
240 if (o == elementData[i]) {
241 return i;
242 }
243 }
244 return -1;
245 }
246
247 /**
248 * Returns an array containing all of the elements in this list
249 * in proper sequence (from first to last element).
250 *
251 * <p>The returned array will be "safe" in that no references to it are
252 * maintained by this list. (In other words, this method must allocate
253 * a new array). The caller is thus free to modify the returned array.
254 *
255 * <p>This method acts as bridge between array-based and collection-based
256 * APIs.
257 *
258 * @return an array containing all of the elements in this list in
259 * proper sequence
260 */
261 public Object[] toArray() {
262 return Arrays.copyOf(elementData, size);
263 }
264
265 /**
266 * Returns an array containing all of the elements in this list in proper
267 * sequence (from first to last element); the runtime type of the returned
268 * array is that of the specified array. If the list fits in the
269 * specified array, it is returned therein. Otherwise, a new array is
270 * allocated with the runtime type of the specified array and the size of
271 * this list.
272 *
273 * <p>If the list fits in the specified array with room to spare
274 * (i.e., the array has more elements than the list), the element in
275 * the array immediately following the end of the collection is set to
276 * <tt>null</tt>. (This is useful in determining the length of the
277 * list <i>only</i> if the caller knows that the list does not contain
278 * any null elements.)
279 *
280 * @param a the array into which the elements of the list are to
281 * be stored, if it is big enough; otherwise, a new array of the
282 * same runtime type is allocated for this purpose.
283 * @return an array containing the elements of the list
284 * @throws ArrayStoreException if the runtime type of the specified array
285 * is not a supertype of the runtime type of every element in
286 * this list
287 * @throws NullPointerException if the specified array is null
288 */
289 @SuppressWarnings("unchecked")
290 public <T> T[] toArray(T[] a) {
291 if (a.length < size)
292 // Make a new array of a's runtime type, but my contents:
293 return (T[]) Arrays.copyOf(elementData, size, a.getClass());
294 System.arraycopy(elementData, 0, a, 0, size);
295 if (a.length > size)
296 a[size] = null;
297 return a;
298 }
299
300 // Positional Access Operations
301
302 /**
303 * Returns the element at the specified position in this list.
304 *
305 * @param index index of the element to return
306 * @return the element at the specified position in this list
307 * @throws IndexOutOfBoundsException {@inheritDoc}
308 */
309 public E get(int index) {
310 rangeCheck(index);
311
312 @SuppressWarnings("unchecked")
313 E rv = (E) elementData[index];
314 return rv;
315 }
316
317 /**
318 * Replaces the element at the specified position in this list with
319 * the specified element.
320 *
321 * @param index index of the element to replace
322 * @param element element to be stored at the specified position
323 * @return the element previously at the specified position
324 * @throws IndexOutOfBoundsException {@inheritDoc}
325 */
326 public E set(int index, E element) {
327 rangeCheck(index);
328
329 @SuppressWarnings("unchecked")
330 E oldValue = (E) elementData[index];
331 elementData[index] = element;
332 return oldValue;
333 }
334
335 /**
336 * Appends the specified element to the end of this list.
337 *
338 * @param e element to be appended to this list
339 * @return <tt>true</tt> (as specified by {@link Collection#add})
340 */
341 public boolean add(E e) {
342 ensureCapacity(size + 1); // Increments modCount!!
343 elementData[size++] = e;
344 return true;
345 }
346
347 /**
348 * Inserts the specified element at the specified position in this
349 * list. Shifts the element currently at that position (if any) and
350 * any subsequent elements to the right (adds one to their indices).
351 *
352 * @param index index at which the specified element is to be inserted
353 * @param element element to be inserted
354 * @throws IndexOutOfBoundsException {@inheritDoc}
355 */
356 public void add(int index, E element) {
357 rangeCheckForAdd(index);
358
359 ensureCapacity(size+1); // Increments modCount!!
360 System.arraycopy(elementData, index, elementData, index + 1,
361 size - index);
362 elementData[index] = element;
363 size++;
364 }
365
366 /**
367 * Removes the element at the specified position in this list.
368 * Shifts any subsequent elements to the left (subtracts one from their
369 * indices).
370 *
371 * @param index the index of the element to be removed
372 * @return the element that was removed from the list
373 * @throws IndexOutOfBoundsException {@inheritDoc}
374 */
375 public E remove(int index) {
376 rangeCheck(index);
377
378 modCount++;
379 @SuppressWarnings("unchecked")
380 E oldValue = (E) elementData[index];
381
382 int numMoved = size - index - 1;
383 if (numMoved > 0)
384 System.arraycopy(elementData, index+1, elementData, index,
385 numMoved);
386 elementData[--size] = null; // Let gc do its work
387
388 return oldValue;
389 }
390
391 /**
392 * Removes the first occurrence of the specified element from this list,
393 * if it is present. If the list does not contain the element, it is
394 * unchanged. More formally, removes the element with the lowest index
395 * <tt>i</tt> such that
396 * <tt>(o==null ? get(i)==null : o == get(i))</tt>
397 * (if such an element exists). Returns <tt>true</tt> if this list
398 * contained the specified element (or equivalently, if this list
399 * changed as a result of the call).
400 *
401 * @param o element to be removed from this list, if present
402 * @return <tt>true</tt> if this list contained the specified element
403 */
404 public boolean remove(Object o) {
405 for (int index = 0; index < size; index++) {
406 if (o == elementData[index]) {
407 fastRemove(index);
408 return true;
409 }
410 }
411 return false;
412 }
413
414 /*
415 * Private remove method that skips bounds checking and does not
416 * return the value removed.
417 */
418 private void fastRemove(int index) {
419 modCount++;
420 int numMoved = size - index - 1;
421 if (numMoved > 0)
422 System.arraycopy(elementData, index+1, elementData, index,
423 numMoved);
424 elementData[--size] = null; // Let gc do its work
425 }
426
427 /**
428 * Removes all of the elements from this list. The list will
429 * be empty after this call returns.
430 */
431 public void clear() {
432 modCount++;
433
434 // Let gc do its work
435 for (int i = 0; i < size; i++)
436 elementData[i] = null;
437
438 size = 0;
439 }
440
441 /**
442 * Appends all of the elements in the specified collection to the end of
443 * this list, in the order that they are returned by the
444 * specified collection's Iterator. The behavior of this operation is
445 * undefined if the specified collection is modified while the operation
446 * is in progress. (This implies that the behavior of this call is
447 * undefined if the specified collection is this list, and this
448 * list is nonempty.)
449 *
450 * @param c collection containing elements to be added to this list
451 * @return <tt>true</tt> if this list changed as a result of the call
452 * @throws NullPointerException if the specified collection is null
453 */
454 public boolean addAll(Collection<? extends E> c) {
455 Object[] a = c.toArray();
456 int numNew = a.length;
457 ensureCapacity(size + numNew); // Increments modCount
458 System.arraycopy(a, 0, elementData, size, numNew);
459 size += numNew;
460 return numNew != 0;
461 }
462
463 /**
464 * Inserts all of the elements in the specified collection into this
465 * list, starting at the specified position. Shifts the element
466 * currently at that position (if any) and any subsequent elements to
467 * the right (increases their indices). The new elements will appear
468 * in the list in the order that they are returned by the
469 * specified collection's iterator.
470 *
471 * @param index index at which to insert the first element from the
472 * specified collection
473 * @param c collection containing elements to be added to this list
474 * @return <tt>true</tt> if this list changed as a result of the call
475 * @throws IndexOutOfBoundsException {@inheritDoc}
476 * @throws NullPointerException if the specified collection is null
477 */
478 public boolean addAll(int index, Collection<? extends E> c) {
479 rangeCheckForAdd(index);
480
481 Object[] a = c.toArray();
482 int numNew = a.length;
483 ensureCapacity(size + numNew); // Increments modCount
484
485 int numMoved = size - index;
486 if (numMoved > 0) {
487 System.arraycopy(elementData, index, elementData, index + numNew, numMoved);
488 }
489
490 System.arraycopy(a, 0, elementData, index, numNew);
491 size += numNew;
492 return numNew != 0;
493 }
494
495 /**
496 * Removes from this list all of the elements whose index is between
497 * <tt>fromIndex</tt>, inclusive, and <tt>toIndex</tt>, exclusive.
498 * Shifts any succeeding elements to the left (reduces their index).
499 * This call shortens the list by <tt>(toIndex - fromIndex)</tt> elements.
500 * (If <tt>toIndex==fromIndex</tt>, this operation has no effect.)
501 *
502 * @param fromIndex index of first element to be removed
503 * @param toIndex index after last element to be removed
504 * @throws IndexOutOfBoundsException if fromIndex or toIndex out of
505 * range (fromIndex < 0 || fromIndex >= size() || toIndex
506 * > size() || toIndex < fromIndex)
507 */
508 protected void removeRange(int fromIndex, int toIndex) {
509 modCount++;
510 int numMoved = size - toIndex;
511 System.arraycopy(elementData, toIndex, elementData, fromIndex,
512 numMoved);
513
514 // Let gc do its work
515 int newSize = size - (toIndex-fromIndex);
516 while (size != newSize)
517 elementData[--size] = null;
518 }
519
520 /**
521 * Checks if the given index is in range. If not, throws an appropriate
522 * runtime exception. This method does *not* check if the index is
523 * negative: It is always used immediately prior to an array access,
524 * which throws an ArrayIndexOutOfBoundsException if index is negative.
525 */
526 private void rangeCheck(int index) {
527 if (index >= size)
528 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
529 }
530
531 /**
532 * A version of rangeCheck used by add and addAll.
533 */
534 private void rangeCheckForAdd(int index) {
535 if (index > size || index < 0)
536 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
537 }
538
539 /**
540 * Constructs an IndexOutOfBoundsException detail message.
541 * Of the many possible refactorings of the error handling code,
542 * this "outlining" performs best with both server and client VMs.
543 */
544 private String outOfBoundsMsg(int index) {
545 return "Index: "+index+", Size: "+size;
546 }
547 }