1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation. Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25 /*
26 * Written by Doug Lea with assistance from members of JCP JSR-166
27 * Expert Group. Adapted and released, under explicit permission,
28 * from JDK ArrayList.java which carries the following copyright:
29 *
30 * Copyright 1997 by Sun Microsystems, Inc.,
31 * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
32 * All rights reserved.
33 */
34
35 package java.util.concurrent;
36
37 import java.lang.invoke.VarHandle;
38 import java.lang.reflect.Field;
39 import java.util.Arrays;
40 import java.util.Collection;
41 import java.util.Comparator;
42 import java.util.ConcurrentModificationException;
43 import java.util.Iterator;
44 import java.util.List;
45 import java.util.ListIterator;
46 import java.util.NoSuchElementException;
47 import java.util.Objects;
48 import java.util.RandomAccess;
49 import java.util.Spliterator;
50 import java.util.Spliterators;
51 import java.util.function.Consumer;
52 import java.util.function.Predicate;
53 import java.util.function.UnaryOperator;
54 import jdk.internal.misc.SharedSecrets;
55
56 /**
57 * A thread-safe variant of {@link java.util.ArrayList} in which all mutative
58 * operations ({@code add}, {@code set}, and so on) are implemented by
59 * making a fresh copy of the underlying array.
60 *
61 * <p>This is ordinarily too costly, but may be <em>more</em> efficient
62 * than alternatives when traversal operations vastly outnumber
63 * mutations, and is useful when you cannot or don't want to
64 * synchronize traversals, yet need to preclude interference among
65 * concurrent threads. The "snapshot" style iterator method uses a
66 * reference to the state of the array at the point that the iterator
67 * was created. This array never changes during the lifetime of the
68 * iterator, so interference is impossible and the iterator is
69 * guaranteed not to throw {@code ConcurrentModificationException}.
70 * The iterator will not reflect additions, removals, or changes to
71 * the list since the iterator was created. Element-changing
72 * operations on iterators themselves ({@code remove}, {@code set}, and
73 * {@code add}) are not supported. These methods throw
74 * {@code UnsupportedOperationException}.
75 *
76 * <p>All elements are permitted, including {@code null}.
77 *
78 * <p>Memory consistency effects: As with other concurrent
79 * collections, actions in a thread prior to placing an object into a
80 * {@code CopyOnWriteArrayList}
81 * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
82 * actions subsequent to the access or removal of that element from
83 * the {@code CopyOnWriteArrayList} in another thread.
84 *
85 * <p>This class is a member of the
86 * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
87 * Java Collections Framework</a>.
88 *
89 * @since 1.5
90 * @author Doug Lea
91 * @param <E> the type of elements held in this list
92 */
93 public class CopyOnWriteArrayList<E>
94 implements List<E>, RandomAccess, Cloneable, java.io.Serializable {
95 private static final long serialVersionUID = 8673264195747942595L;
96
97 /**
98 * The lock protecting all mutators. (We have a mild preference
99 * for builtin monitors over ReentrantLock when either will do.)
100 */
101 final transient Object lock = new Object();
102
103 /** The array, accessed only via getArray/setArray. */
104 private transient volatile Object[] array;
105
106 /**
107 * Gets the array. Non-private so as to also be accessible
108 * from CopyOnWriteArraySet class.
109 */
110 final Object[] getArray() {
111 return array;
112 }
113
114 /**
115 * Sets the array.
116 */
117 final void setArray(Object[] a) {
118 array = a;
119 }
120
121 /**
122 * Creates an empty list.
123 */
124 public CopyOnWriteArrayList() {
125 setArray(new Object[0]);
126 }
127
128 /**
129 * Creates a list containing the elements of the specified
130 * collection, in the order they are returned by the collection's
131 * iterator.
132 *
133 * @param c the collection of initially held elements
134 * @throws NullPointerException if the specified collection is null
135 */
136 public CopyOnWriteArrayList(Collection<? extends E> c) {
137 Object[] es;
138 if (c.getClass() == CopyOnWriteArrayList.class)
139 es = ((CopyOnWriteArrayList<?>)c).getArray();
140 else {
141 es = c.toArray();
142 // defend against c.toArray (incorrectly) not returning Object[]
143 // (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652)
144 if (es.getClass() != Object[].class)
145 es = Arrays.copyOf(es, es.length, Object[].class);
146 }
147 setArray(es);
148 }
149
150 /**
151 * Creates a list holding a copy of the given array.
152 *
153 * @param toCopyIn the array (a copy of this array is used as the
154 * internal array)
155 * @throws NullPointerException if the specified array is null
156 */
157 public CopyOnWriteArrayList(E[] toCopyIn) {
158 setArray(Arrays.copyOf(toCopyIn, toCopyIn.length, Object[].class));
159 }
160
161 /**
162 * Returns the number of elements in this list.
163 *
164 * @return the number of elements in this list
165 */
166 public int size() {
167 return getArray().length;
168 }
169
170 /**
171 * Returns {@code true} if this list contains no elements.
172 *
173 * @return {@code true} if this list contains no elements
174 */
175 public boolean isEmpty() {
176 return size() == 0;
177 }
178
179 /**
180 * static version of indexOf, to allow repeated calls without
181 * needing to re-acquire array each time.
182 * @param o element to search for
183 * @param es the array
184 * @param from first index to search
185 * @param to one past last index to search
186 * @return index of element, or -1 if absent
187 */
188 private static int indexOfRange(Object o, Object[] es, int from, int to) {
189 if (o == null) {
190 for (int i = from; i < to; i++)
191 if (es[i] == null)
192 return i;
193 } else {
194 for (int i = from; i < to; i++)
195 if (o.equals(es[i]))
196 return i;
197 }
198 return -1;
199 }
200
201 /**
202 * static version of lastIndexOf.
203 * @param o element to search for
204 * @param es the array
205 * @param from index of first element of range, last element to search
206 * @param to one past last element of range, first element to search
207 * @return index of element, or -1 if absent
208 */
209 private static int lastIndexOfRange(Object o, Object[] es, int from, int to) {
210 if (o == null) {
211 for (int i = to - 1; i >= from; i--)
212 if (es[i] == null)
213 return i;
214 } else {
215 for (int i = to - 1; i >= from; i--)
216 if (o.equals(es[i]))
217 return i;
218 }
219 return -1;
220 }
221
222 /**
223 * Returns {@code true} if this list contains the specified element.
224 * More formally, returns {@code true} if and only if this list contains
225 * at least one element {@code e} such that {@code Objects.equals(o, e)}.
226 *
227 * @param o element whose presence in this list is to be tested
228 * @return {@code true} if this list contains the specified element
229 */
230 public boolean contains(Object o) {
231 return indexOf(o) >= 0;
232 }
233
234 /**
235 * {@inheritDoc}
236 */
237 public int indexOf(Object o) {
238 Object[] es = getArray();
239 return indexOfRange(o, es, 0, es.length);
240 }
241
242 /**
243 * Returns the index of the first occurrence of the specified element in
244 * this list, searching forwards from {@code index}, or returns -1 if
245 * the element is not found.
246 * More formally, returns the lowest index {@code i} such that
247 * {@code i >= index && Objects.equals(get(i), e)},
248 * or -1 if there is no such index.
249 *
250 * @param e element to search for
251 * @param index index to start searching from
252 * @return the index of the first occurrence of the element in
253 * this list at position {@code index} or later in the list;
254 * {@code -1} if the element is not found.
255 * @throws IndexOutOfBoundsException if the specified index is negative
256 */
257 public int indexOf(E e, int index) {
258 Object[] es = getArray();
259 return indexOfRange(e, es, index, es.length);
260 }
261
262 /**
263 * {@inheritDoc}
264 */
265 public int lastIndexOf(Object o) {
266 Object[] es = getArray();
267 return lastIndexOfRange(o, es, 0, es.length);
268 }
269
270 /**
271 * Returns the index of the last occurrence of the specified element in
272 * this list, searching backwards from {@code index}, or returns -1 if
273 * the element is not found.
274 * More formally, returns the highest index {@code i} such that
275 * {@code i <= index && Objects.equals(get(i), e)},
276 * or -1 if there is no such index.
277 *
278 * @param e element to search for
279 * @param index index to start searching backwards from
280 * @return the index of the last occurrence of the element at position
281 * less than or equal to {@code index} in this list;
282 * -1 if the element is not found.
283 * @throws IndexOutOfBoundsException if the specified index is greater
284 * than or equal to the current size of this list
285 */
286 public int lastIndexOf(E e, int index) {
287 Object[] es = getArray();
288 return lastIndexOfRange(e, es, 0, index + 1);
289 }
290
291 /**
292 * Returns a shallow copy of this list. (The elements themselves
293 * are not copied.)
294 *
295 * @return a clone of this list
296 */
297 public Object clone() {
298 try {
299 @SuppressWarnings("unchecked")
300 CopyOnWriteArrayList<E> clone =
301 (CopyOnWriteArrayList<E>) super.clone();
302 clone.resetLock();
303 // Unlike in readObject, here we cannot visibility-piggyback on the
304 // volatile write in setArray().
305 VarHandle.releaseFence();
306 return clone;
307 } catch (CloneNotSupportedException e) {
308 // this shouldn't happen, since we are Cloneable
309 throw new InternalError();
310 }
311 }
312
313 /**
314 * Returns an array containing all of the elements in this list
315 * in proper sequence (from first to last element).
316 *
317 * <p>The returned array will be "safe" in that no references to it are
318 * maintained by this list. (In other words, this method must allocate
319 * a new array). The caller is thus free to modify the returned array.
320 *
321 * <p>This method acts as bridge between array-based and collection-based
322 * APIs.
323 *
324 * @return an array containing all the elements in this list
325 */
326 public Object[] toArray() {
327 return getArray().clone();
328 }
329
330 /**
331 * Returns an array containing all of the elements in this list in
332 * proper sequence (from first to last element); the runtime type of
333 * the returned array is that of the specified array. If the list fits
334 * in the specified array, it is returned therein. Otherwise, a new
335 * array is allocated with the runtime type of the specified array and
336 * the size of this list.
337 *
338 * <p>If this list fits in the specified array with room to spare
339 * (i.e., the array has more elements than this list), the element in
340 * the array immediately following the end of the list is set to
341 * {@code null}. (This is useful in determining the length of this
342 * list <i>only</i> if the caller knows that this list does not contain
343 * any null elements.)
344 *
345 * <p>Like the {@link #toArray()} method, this method acts as bridge between
346 * array-based and collection-based APIs. Further, this method allows
347 * precise control over the runtime type of the output array, and may,
348 * under certain circumstances, be used to save allocation costs.
349 *
350 * <p>Suppose {@code x} is a list known to contain only strings.
351 * The following code can be used to dump the list into a newly
352 * allocated array of {@code String}:
353 *
354 * <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
355 *
356 * Note that {@code toArray(new Object[0])} is identical in function to
357 * {@code toArray()}.
358 *
359 * @param a the array into which the elements of the list are to
360 * be stored, if it is big enough; otherwise, a new array of the
361 * same runtime type is allocated for this purpose.
362 * @return an array containing all the elements in this list
363 * @throws ArrayStoreException if the runtime type of the specified array
364 * is not a supertype of the runtime type of every element in
365 * this list
366 * @throws NullPointerException if the specified array is null
367 */
368 @SuppressWarnings("unchecked")
369 public <T> T[] toArray(T[] a) {
370 Object[] es = getArray();
371 int len = es.length;
372 if (a.length < len)
373 return (T[]) Arrays.copyOf(es, len, a.getClass());
374 else {
375 System.arraycopy(es, 0, a, 0, len);
376 if (a.length > len)
377 a[len] = null;
378 return a;
379 }
380 }
381
382 // Positional Access Operations
383
384 @SuppressWarnings("unchecked")
385 static <E> E elementAt(Object[] a, int index) {
386 return (E) a[index];
387 }
388
389 static String outOfBounds(int index, int size) {
390 return "Index: " + index + ", Size: " + size;
391 }
392
393 /**
394 * {@inheritDoc}
395 *
396 * @throws IndexOutOfBoundsException {@inheritDoc}
397 */
398 public E get(int index) {
399 return elementAt(getArray(), index);
400 }
401
402 /**
403 * Replaces the element at the specified position in this list with the
404 * specified element.
405 *
406 * @throws IndexOutOfBoundsException {@inheritDoc}
407 */
408 public E set(int index, E element) {
409 synchronized (lock) {
410 Object[] es = getArray();
411 E oldValue = elementAt(es, index);
412
413 if (oldValue != element) {
414 es = es.clone();
415 es[index] = element;
416 }
417 // Ensure volatile write semantics even when oldvalue == element
418 setArray(es);
419 return oldValue;
420 }
421 }
422
423 /**
424 * Appends the specified element to the end of this list.
425 *
426 * @param e element to be appended to this list
427 * @return {@code true} (as specified by {@link Collection#add})
428 */
429 public boolean add(E e) {
430 synchronized (lock) {
431 Object[] es = getArray();
432 int len = es.length;
433 es = Arrays.copyOf(es, len + 1);
434 es[len] = e;
435 setArray(es);
436 return true;
437 }
438 }
439
440 /**
441 * Inserts the specified element at the specified position in this
442 * list. Shifts the element currently at that position (if any) and
443 * any subsequent elements to the right (adds one to their indices).
444 *
445 * @throws IndexOutOfBoundsException {@inheritDoc}
446 */
447 public void add(int index, E element) {
448 synchronized (lock) {
449 Object[] es = getArray();
450 int len = es.length;
451 if (index > len || index < 0)
452 throw new IndexOutOfBoundsException(outOfBounds(index, len));
453 Object[] newElements;
454 int numMoved = len - index;
455 if (numMoved == 0)
456 newElements = Arrays.copyOf(es, len + 1);
457 else {
458 newElements = new Object[len + 1];
459 System.arraycopy(es, 0, newElements, 0, index);
460 System.arraycopy(es, index, newElements, index + 1,
461 numMoved);
462 }
463 newElements[index] = element;
464 setArray(newElements);
465 }
466 }
467
468 /**
469 * Removes the element at the specified position in this list.
470 * Shifts any subsequent elements to the left (subtracts one from their
471 * indices). Returns the element that was removed from the list.
472 *
473 * @throws IndexOutOfBoundsException {@inheritDoc}
474 */
475 public E remove(int index) {
476 synchronized (lock) {
477 Object[] es = getArray();
478 int len = es.length;
479 E oldValue = elementAt(es, index);
480 int numMoved = len - index - 1;
481 Object[] newElements;
482 if (numMoved == 0)
483 newElements = Arrays.copyOf(es, len - 1);
484 else {
485 newElements = new Object[len - 1];
486 System.arraycopy(es, 0, newElements, 0, index);
487 System.arraycopy(es, index + 1, newElements, index,
488 numMoved);
489 }
490 setArray(newElements);
491 return oldValue;
492 }
493 }
494
495 /**
496 * Removes the first occurrence of the specified element from this list,
497 * if it is present. If this list does not contain the element, it is
498 * unchanged. More formally, removes the element with the lowest index
499 * {@code i} such that {@code Objects.equals(o, get(i))}
500 * (if such an element exists). Returns {@code true} if this list
501 * contained the specified element (or equivalently, if this list
502 * changed as a result of the call).
503 *
504 * @param o element to be removed from this list, if present
505 * @return {@code true} if this list contained the specified element
506 */
507 public boolean remove(Object o) {
508 Object[] snapshot = getArray();
509 int index = indexOfRange(o, snapshot, 0, snapshot.length);
510 return index >= 0 && remove(o, snapshot, index);
511 }
512
513 /**
514 * A version of remove(Object) using the strong hint that given
515 * recent snapshot contains o at the given index.
516 */
517 private boolean remove(Object o, Object[] snapshot, int index) {
518 synchronized (lock) {
519 Object[] current = getArray();
520 int len = current.length;
521 if (snapshot != current) findIndex: {
522 int prefix = Math.min(index, len);
523 for (int i = 0; i < prefix; i++) {
524 if (current[i] != snapshot[i]
525 && Objects.equals(o, current[i])) {
526 index = i;
527 break findIndex;
528 }
529 }
530 if (index >= len)
531 return false;
532 if (current[index] == o)
533 break findIndex;
534 index = indexOfRange(o, current, index, len);
535 if (index < 0)
536 return false;
537 }
538 Object[] newElements = new Object[len - 1];
539 System.arraycopy(current, 0, newElements, 0, index);
540 System.arraycopy(current, index + 1,
541 newElements, index,
542 len - index - 1);
543 setArray(newElements);
544 return true;
545 }
546 }
547
548 /**
549 * Removes from this list all of the elements whose index is between
550 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
551 * Shifts any succeeding elements to the left (reduces their index).
552 * This call shortens the list by {@code (toIndex - fromIndex)} elements.
553 * (If {@code toIndex==fromIndex}, this operation has no effect.)
554 *
555 * @param fromIndex index of first element to be removed
556 * @param toIndex index after last element to be removed
557 * @throws IndexOutOfBoundsException if fromIndex or toIndex out of range
558 * ({@code fromIndex < 0 || toIndex > size() || toIndex < fromIndex})
559 */
560 void removeRange(int fromIndex, int toIndex) {
561 synchronized (lock) {
562 Object[] es = getArray();
563 int len = es.length;
564
565 if (fromIndex < 0 || toIndex > len || toIndex < fromIndex)
566 throw new IndexOutOfBoundsException();
567 int newlen = len - (toIndex - fromIndex);
568 int numMoved = len - toIndex;
569 if (numMoved == 0)
570 setArray(Arrays.copyOf(es, newlen));
571 else {
572 Object[] newElements = new Object[newlen];
573 System.arraycopy(es, 0, newElements, 0, fromIndex);
574 System.arraycopy(es, toIndex, newElements,
575 fromIndex, numMoved);
576 setArray(newElements);
577 }
578 }
579 }
580
581 /**
582 * Appends the element, if not present.
583 *
584 * @param e element to be added to this list, if absent
585 * @return {@code true} if the element was added
586 */
587 public boolean addIfAbsent(E e) {
588 Object[] snapshot = getArray();
589 return indexOfRange(e, snapshot, 0, snapshot.length) < 0
590 && addIfAbsent(e, snapshot);
591 }
592
593 /**
594 * A version of addIfAbsent using the strong hint that given
595 * recent snapshot does not contain e.
596 */
597 private boolean addIfAbsent(E e, Object[] snapshot) {
598 synchronized (lock) {
599 Object[] current = getArray();
600 int len = current.length;
601 if (snapshot != current) {
602 // Optimize for lost race to another addXXX operation
603 int common = Math.min(snapshot.length, len);
604 for (int i = 0; i < common; i++)
605 if (current[i] != snapshot[i]
606 && Objects.equals(e, current[i]))
607 return false;
608 if (indexOfRange(e, current, common, len) >= 0)
609 return false;
610 }
611 Object[] newElements = Arrays.copyOf(current, len + 1);
612 newElements[len] = e;
613 setArray(newElements);
614 return true;
615 }
616 }
617
618 /**
619 * Returns {@code true} if this list contains all of the elements of the
620 * specified collection.
621 *
622 * @param c collection to be checked for containment in this list
623 * @return {@code true} if this list contains all of the elements of the
624 * specified collection
625 * @throws NullPointerException if the specified collection is null
626 * @see #contains(Object)
627 */
628 public boolean containsAll(Collection<?> c) {
629 Object[] es = getArray();
630 int len = es.length;
631 for (Object e : c) {
632 if (indexOfRange(e, es, 0, len) < 0)
633 return false;
634 }
635 return true;
636 }
637
638 /**
639 * Removes from this list all of its elements that are contained in
640 * the specified collection. This is a particularly expensive operation
641 * in this class because of the need for an internal temporary array.
642 *
643 * @param c collection containing elements to be removed from this list
644 * @return {@code true} if this list changed as a result of the call
645 * @throws ClassCastException if the class of an element of this list
646 * is incompatible with the specified collection
647 * (<a href="{@docRoot}/java.base/java/util/Collection.html#optional-restrictions">optional</a>)
648 * @throws NullPointerException if this list contains a null element and the
649 * specified collection does not permit null elements
650 * (<a href="{@docRoot}/java.base/java/util/Collection.html#optional-restrictions">optional</a>),
651 * or if the specified collection is null
652 * @see #remove(Object)
653 */
654 public boolean removeAll(Collection<?> c) {
655 Objects.requireNonNull(c);
656 return bulkRemove(e -> c.contains(e));
657 }
658
659 /**
660 * Retains only the elements in this list that are contained in the
661 * specified collection. In other words, removes from this list all of
662 * its elements that are not contained in the specified collection.
663 *
664 * @param c collection containing elements to be retained in this list
665 * @return {@code true} if this list changed as a result of the call
666 * @throws ClassCastException if the class of an element of this list
667 * is incompatible with the specified collection
668 * (<a href="{@docRoot}/java.base/java/util/Collection.html#optional-restrictions">optional</a>)
669 * @throws NullPointerException if this list contains a null element and the
670 * specified collection does not permit null elements
671 * (<a href="{@docRoot}/java.base/java/util/Collection.html#optional-restrictions">optional</a>),
672 * or if the specified collection is null
673 * @see #remove(Object)
674 */
675 public boolean retainAll(Collection<?> c) {
676 Objects.requireNonNull(c);
677 return bulkRemove(e -> !c.contains(e));
678 }
679
680 /**
681 * Appends all of the elements in the specified collection that
682 * are not already contained in this list, to the end of
683 * this list, in the order that they are returned by the
684 * specified collection's iterator.
685 *
686 * @param c collection containing elements to be added to this list
687 * @return the number of elements added
688 * @throws NullPointerException if the specified collection is null
689 * @see #addIfAbsent(Object)
690 */
691 public int addAllAbsent(Collection<? extends E> c) {
692 Object[] cs = c.toArray();
693 if (cs.length == 0)
694 return 0;
695 synchronized (lock) {
696 Object[] es = getArray();
697 int len = es.length;
698 int added = 0;
699 // uniquify and compact elements in cs
700 for (int i = 0; i < cs.length; ++i) {
701 Object e = cs[i];
702 if (indexOfRange(e, es, 0, len) < 0 &&
703 indexOfRange(e, cs, 0, added) < 0)
704 cs[added++] = e;
705 }
706 if (added > 0) {
707 Object[] newElements = Arrays.copyOf(es, len + added);
708 System.arraycopy(cs, 0, newElements, len, added);
709 setArray(newElements);
710 }
711 return added;
712 }
713 }
714
715 /**
716 * Removes all of the elements from this list.
717 * The list will be empty after this call returns.
718 */
719 public void clear() {
720 synchronized (lock) {
721 setArray(new Object[0]);
722 }
723 }
724
725 /**
726 * Appends all of the elements in the specified collection to the end
727 * of this list, in the order that they are returned by the specified
728 * collection's iterator.
729 *
730 * @param c collection containing elements to be added to this list
731 * @return {@code true} if this list changed as a result of the call
732 * @throws NullPointerException if the specified collection is null
733 * @see #add(Object)
734 */
735 public boolean addAll(Collection<? extends E> c) {
736 Object[] cs = (c.getClass() == CopyOnWriteArrayList.class) ?
737 ((CopyOnWriteArrayList<?>)c).getArray() : c.toArray();
738 if (cs.length == 0)
739 return false;
740 synchronized (lock) {
741 Object[] es = getArray();
742 int len = es.length;
743 Object[] newElements;
744 if (len == 0 && cs.getClass() == Object[].class)
745 newElements = cs;
746 else {
747 newElements = Arrays.copyOf(es, len + cs.length);
748 System.arraycopy(cs, 0, newElements, len, cs.length);
749 }
750 setArray(newElements);
751 return true;
752 }
753 }
754
755 /**
756 * Inserts all of the elements in the specified collection into this
757 * list, starting at the specified position. Shifts the element
758 * currently at that position (if any) and any subsequent elements to
759 * the right (increases their indices). The new elements will appear
760 * in this list in the order that they are returned by the
761 * specified collection's iterator.
762 *
763 * @param index index at which to insert the first element
764 * from the specified collection
765 * @param c collection containing elements to be added to this list
766 * @return {@code true} if this list changed as a result of the call
767 * @throws IndexOutOfBoundsException {@inheritDoc}
768 * @throws NullPointerException if the specified collection is null
769 * @see #add(int,Object)
770 */
771 public boolean addAll(int index, Collection<? extends E> c) {
772 Object[] cs = c.toArray();
773 synchronized (lock) {
774 Object[] es = getArray();
775 int len = es.length;
776 if (index > len || index < 0)
777 throw new IndexOutOfBoundsException(outOfBounds(index, len));
778 if (cs.length == 0)
779 return false;
780 int numMoved = len - index;
781 Object[] newElements;
782 if (numMoved == 0)
783 newElements = Arrays.copyOf(es, len + cs.length);
784 else {
785 newElements = new Object[len + cs.length];
786 System.arraycopy(es, 0, newElements, 0, index);
787 System.arraycopy(es, index,
788 newElements, index + cs.length,
789 numMoved);
790 }
791 System.arraycopy(cs, 0, newElements, index, cs.length);
792 setArray(newElements);
793 return true;
794 }
795 }
796
797 /**
798 * @throws NullPointerException {@inheritDoc}
799 */
800 public void forEach(Consumer<? super E> action) {
801 Objects.requireNonNull(action);
802 for (Object x : getArray()) {
803 @SuppressWarnings("unchecked") E e = (E) x;
804 action.accept(e);
805 }
806 }
807
808 /**
809 * @throws NullPointerException {@inheritDoc}
810 */
811 public boolean removeIf(Predicate<? super E> filter) {
812 Objects.requireNonNull(filter);
813 return bulkRemove(filter);
814 }
815
816 // A tiny bit set implementation
817
818 private static long[] nBits(int n) {
819 return new long[((n - 1) >> 6) + 1];
820 }
821 private static void setBit(long[] bits, int i) {
822 bits[i >> 6] |= 1L << i;
823 }
824 private static boolean isClear(long[] bits, int i) {
825 return (bits[i >> 6] & (1L << i)) == 0;
826 }
827
828 private boolean bulkRemove(Predicate<? super E> filter) {
829 synchronized (lock) {
830 return bulkRemove(filter, 0, getArray().length);
831 }
832 }
833
834 boolean bulkRemove(Predicate<? super E> filter, int i, int end) {
835 // assert Thread.holdsLock(lock);
836 final Object[] es = getArray();
837 // Optimize for initial run of survivors
838 for (; i < end && !filter.test(elementAt(es, i)); i++)
839 ;
840 if (i < end) {
841 final int beg = i;
842 final long[] deathRow = nBits(end - beg);
843 int deleted = 1;
844 deathRow[0] = 1L; // set bit 0
845 for (i = beg + 1; i < end; i++)
846 if (filter.test(elementAt(es, i))) {
847 setBit(deathRow, i - beg);
848 deleted++;
849 }
850 // Did filter reentrantly modify the list?
851 if (es != getArray())
852 throw new ConcurrentModificationException();
853 final Object[] newElts = Arrays.copyOf(es, es.length - deleted);
854 int w = beg;
855 for (i = beg; i < end; i++)
856 if (isClear(deathRow, i - beg))
857 newElts[w++] = es[i];
858 System.arraycopy(es, i, newElts, w, es.length - i);
859 setArray(newElts);
860 return true;
861 } else {
862 if (es != getArray())
863 throw new ConcurrentModificationException();
864 return false;
865 }
866 }
867
868 public void replaceAll(UnaryOperator<E> operator) {
869 synchronized (lock) {
870 replaceAllRange(operator, 0, getArray().length);
871 }
872 }
873
874 void replaceAllRange(UnaryOperator<E> operator, int i, int end) {
875 // assert Thread.holdsLock(lock);
876 Objects.requireNonNull(operator);
877 final Object[] es = getArray().clone();
878 for (; i < end; i++)
879 es[i] = operator.apply(elementAt(es, i));
880 setArray(es);
881 }
882
883 public void sort(Comparator<? super E> c) {
884 synchronized (lock) {
885 sortRange(c, 0, getArray().length);
886 }
887 }
888
889 @SuppressWarnings("unchecked")
890 void sortRange(Comparator<? super E> c, int i, int end) {
891 // assert Thread.holdsLock(lock);
892 final Object[] es = getArray().clone();
893 Arrays.sort(es, i, end, (Comparator<Object>)c);
894 setArray(es);
895 }
896
897 /**
898 * Saves this list to a stream (that is, serializes it).
899 *
900 * @param s the stream
901 * @throws java.io.IOException if an I/O error occurs
902 * @serialData The length of the array backing the list is emitted
903 * (int), followed by all of its elements (each an Object)
904 * in the proper order.
905 */
906 private void writeObject(java.io.ObjectOutputStream s)
907 throws java.io.IOException {
908
909 s.defaultWriteObject();
910
911 Object[] es = getArray();
912 // Write out array length
913 s.writeInt(es.length);
914
915 // Write out all elements in the proper order.
916 for (Object element : es)
917 s.writeObject(element);
918 }
919
920 /**
921 * Reconstitutes this list from a stream (that is, deserializes it).
922 * @param s the stream
923 * @throws ClassNotFoundException if the class of a serialized object
924 * could not be found
925 * @throws java.io.IOException if an I/O error occurs
926 */
927 private void readObject(java.io.ObjectInputStream s)
928 throws java.io.IOException, ClassNotFoundException {
929
930 s.defaultReadObject();
931
932 // bind to new lock
933 resetLock();
934
935 // Read in array length and allocate array
936 int len = s.readInt();
937 SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, len);
938 Object[] es = new Object[len];
939
940 // Read in all elements in the proper order.
941 for (int i = 0; i < len; i++)
942 es[i] = s.readObject();
943 setArray(es);
944 }
945
946 /**
947 * Returns a string representation of this list. The string
948 * representation consists of the string representations of the list's
949 * elements in the order they are returned by its iterator, enclosed in
950 * square brackets ({@code "[]"}). Adjacent elements are separated by
951 * the characters {@code ", "} (comma and space). Elements are
952 * converted to strings as by {@link String#valueOf(Object)}.
953 *
954 * @return a string representation of this list
955 */
956 public String toString() {
957 return Arrays.toString(getArray());
958 }
959
960 /**
961 * Compares the specified object with this list for equality.
962 * Returns {@code true} if the specified object is the same object
963 * as this object, or if it is also a {@link List} and the sequence
964 * of elements returned by an {@linkplain List#iterator() iterator}
965 * over the specified list is the same as the sequence returned by
966 * an iterator over this list. The two sequences are considered to
967 * be the same if they have the same length and corresponding
968 * elements at the same position in the sequence are <em>equal</em>.
969 * Two elements {@code e1} and {@code e2} are considered
970 * <em>equal</em> if {@code Objects.equals(e1, e2)}.
971 *
972 * @param o the object to be compared for equality with this list
973 * @return {@code true} if the specified object is equal to this list
974 */
975 public boolean equals(Object o) {
976 if (o == this)
977 return true;
978 if (!(o instanceof List))
979 return false;
980
981 List<?> list = (List<?>)o;
982 Iterator<?> it = list.iterator();
983 for (Object element : getArray())
984 if (!it.hasNext() || !Objects.equals(element, it.next()))
985 return false;
986 return !it.hasNext();
987 }
988
989 private static int hashCodeOfRange(Object[] es, int from, int to) {
990 int hashCode = 1;
991 for (int i = from; i < to; i++) {
992 Object x = es[i];
993 hashCode = 31 * hashCode + (x == null ? 0 : x.hashCode());
994 }
995 return hashCode;
996 }
997
998 /**
999 * Returns the hash code value for this list.
1000 *
1001 * <p>This implementation uses the definition in {@link List#hashCode}.
1002 *
1003 * @return the hash code value for this list
1004 */
1005 public int hashCode() {
1006 Object[] es = getArray();
1007 return hashCodeOfRange(es, 0, es.length);
1008 }
1009
1010 /**
1011 * Returns an iterator over the elements in this list in proper sequence.
1012 *
1013 * <p>The returned iterator provides a snapshot of the state of the list
1014 * when the iterator was constructed. No synchronization is needed while
1015 * traversing the iterator. The iterator does <em>NOT</em> support the
1016 * {@code remove} method.
1017 *
1018 * @return an iterator over the elements in this list in proper sequence
1019 */
1020 public Iterator<E> iterator() {
1021 return new COWIterator<E>(getArray(), 0);
1022 }
1023
1024 /**
1025 * {@inheritDoc}
1026 *
1027 * <p>The returned iterator provides a snapshot of the state of the list
1028 * when the iterator was constructed. No synchronization is needed while
1029 * traversing the iterator. The iterator does <em>NOT</em> support the
1030 * {@code remove}, {@code set} or {@code add} methods.
1031 */
1032 public ListIterator<E> listIterator() {
1033 return new COWIterator<E>(getArray(), 0);
1034 }
1035
1036 /**
1037 * {@inheritDoc}
1038 *
1039 * <p>The returned iterator provides a snapshot of the state of the list
1040 * when the iterator was constructed. No synchronization is needed while
1041 * traversing the iterator. The iterator does <em>NOT</em> support the
1042 * {@code remove}, {@code set} or {@code add} methods.
1043 *
1044 * @throws IndexOutOfBoundsException {@inheritDoc}
1045 */
1046 public ListIterator<E> listIterator(int index) {
1047 Object[] es = getArray();
1048 int len = es.length;
1049 if (index < 0 || index > len)
1050 throw new IndexOutOfBoundsException(outOfBounds(index, len));
1051
1052 return new COWIterator<E>(es, index);
1053 }
1054
1055 /**
1056 * Returns a {@link Spliterator} over the elements in this list.
1057 *
1058 * <p>The {@code Spliterator} reports {@link Spliterator#IMMUTABLE},
1059 * {@link Spliterator#ORDERED}, {@link Spliterator#SIZED}, and
1060 * {@link Spliterator#SUBSIZED}.
1061 *
1062 * <p>The spliterator provides a snapshot of the state of the list
1063 * when the spliterator was constructed. No synchronization is needed while
1064 * operating on the spliterator.
1065 *
1066 * @return a {@code Spliterator} over the elements in this list
1067 * @since 1.8
1068 */
1069 public Spliterator<E> spliterator() {
1070 return Spliterators.spliterator
1071 (getArray(), Spliterator.IMMUTABLE | Spliterator.ORDERED);
1072 }
1073
1074 static final class COWIterator<E> implements ListIterator<E> {
1075 /** Snapshot of the array */
1076 private final Object[] snapshot;
1077 /** Index of element to be returned by subsequent call to next. */
1078 private int cursor;
1079
1080 COWIterator(Object[] es, int initialCursor) {
1081 cursor = initialCursor;
1082 snapshot = es;
1083 }
1084
1085 public boolean hasNext() {
1086 return cursor < snapshot.length;
1087 }
1088
1089 public boolean hasPrevious() {
1090 return cursor > 0;
1091 }
1092
1093 @SuppressWarnings("unchecked")
1094 public E next() {
1095 if (! hasNext())
1096 throw new NoSuchElementException();
1097 return (E) snapshot[cursor++];
1098 }
1099
1100 @SuppressWarnings("unchecked")
1101 public E previous() {
1102 if (! hasPrevious())
1103 throw new NoSuchElementException();
1104 return (E) snapshot[--cursor];
1105 }
1106
1107 public int nextIndex() {
1108 return cursor;
1109 }
1110
1111 public int previousIndex() {
1112 return cursor - 1;
1113 }
1114
1115 /**
1116 * Not supported. Always throws UnsupportedOperationException.
1117 * @throws UnsupportedOperationException always; {@code remove}
1118 * is not supported by this iterator.
1119 */
1120 public void remove() {
1121 throw new UnsupportedOperationException();
1122 }
1123
1124 /**
1125 * Not supported. Always throws UnsupportedOperationException.
1126 * @throws UnsupportedOperationException always; {@code set}
1127 * is not supported by this iterator.
1128 */
1129 public void set(E e) {
1130 throw new UnsupportedOperationException();
1131 }
1132
1133 /**
1134 * Not supported. Always throws UnsupportedOperationException.
1135 * @throws UnsupportedOperationException always; {@code add}
1136 * is not supported by this iterator.
1137 */
1138 public void add(E e) {
1139 throw new UnsupportedOperationException();
1140 }
1141
1142 @Override
1143 public void forEachRemaining(Consumer<? super E> action) {
1144 Objects.requireNonNull(action);
1145 final int size = snapshot.length;
1146 int i = cursor;
1147 cursor = size;
1148 for (; i < size; i++)
1149 action.accept(elementAt(snapshot, i));
1150 }
1151 }
1152
1153 /**
1154 * Returns a view of the portion of this list between
1155 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
1156 * The returned list is backed by this list, so changes in the
1157 * returned list are reflected in this list.
1158 *
1159 * <p>The semantics of the list returned by this method become
1160 * undefined if the backing list (i.e., this list) is modified in
1161 * any way other than via the returned list.
1162 *
1163 * @param fromIndex low endpoint (inclusive) of the subList
1164 * @param toIndex high endpoint (exclusive) of the subList
1165 * @return a view of the specified range within this list
1166 * @throws IndexOutOfBoundsException {@inheritDoc}
1167 */
1168 public List<E> subList(int fromIndex, int toIndex) {
1169 synchronized (lock) {
1170 Object[] es = getArray();
1171 int len = es.length;
1172 int size = toIndex - fromIndex;
1173 if (fromIndex < 0 || toIndex > len || size < 0)
1174 throw new IndexOutOfBoundsException();
1175 return new COWSubList(es, fromIndex, size);
1176 }
1177 }
1178
1179 /**
1180 * Sublist for CopyOnWriteArrayList.
1181 */
1182 private class COWSubList implements List<E>, RandomAccess {
1183 private final int offset;
1184 private int size;
1185 private Object[] expectedArray;
1186
1187 COWSubList(Object[] es, int offset, int size) {
1188 // assert Thread.holdsLock(lock);
1189 expectedArray = es;
1190 this.offset = offset;
1191 this.size = size;
1192 }
1193
1194 private void checkForComodification() {
1195 // assert Thread.holdsLock(lock);
1196 if (getArray() != expectedArray)
1197 throw new ConcurrentModificationException();
1198 }
1199
1200 private Object[] getArrayChecked() {
1201 // assert Thread.holdsLock(lock);
1202 Object[] a = getArray();
1203 if (a != expectedArray)
1204 throw new ConcurrentModificationException();
1205 return a;
1206 }
1207
1208 private void rangeCheck(int index) {
1209 // assert Thread.holdsLock(lock);
1210 if (index < 0 || index >= size)
1211 throw new IndexOutOfBoundsException(outOfBounds(index, size));
1212 }
1213
1214 private void rangeCheckForAdd(int index) {
1215 // assert Thread.holdsLock(lock);
1216 if (index < 0 || index > size)
1217 throw new IndexOutOfBoundsException(outOfBounds(index, size));
1218 }
1219
1220 public Object[] toArray() {
1221 final Object[] es;
1222 final int offset;
1223 final int size;
1224 synchronized (lock) {
1225 es = getArrayChecked();
1226 offset = this.offset;
1227 size = this.size;
1228 }
1229 return Arrays.copyOfRange(es, offset, offset + size);
1230 }
1231
1232 @SuppressWarnings("unchecked")
1233 public <T> T[] toArray(T[] a) {
1234 final Object[] es;
1235 final int offset;
1236 final int size;
1237 synchronized (lock) {
1238 es = getArrayChecked();
1239 offset = this.offset;
1240 size = this.size;
1241 }
1242 if (a.length < size)
1243 return (T[]) Arrays.copyOfRange(
1244 es, offset, offset + size, a.getClass());
1245 else {
1246 System.arraycopy(es, offset, a, 0, size);
1247 if (a.length > size)
1248 a[size] = null;
1249 return a;
1250 }
1251 }
1252
1253 public int indexOf(Object o) {
1254 final Object[] es;
1255 final int offset;
1256 final int size;
1257 synchronized (lock) {
1258 es = getArrayChecked();
1259 offset = this.offset;
1260 size = this.size;
1261 }
1262 int i = indexOfRange(o, es, offset, offset + size);
1263 return (i == -1) ? -1 : i - offset;
1264 }
1265
1266 public int lastIndexOf(Object o) {
1267 final Object[] es;
1268 final int offset;
1269 final int size;
1270 synchronized (lock) {
1271 es = getArrayChecked();
1272 offset = this.offset;
1273 size = this.size;
1274 }
1275 int i = lastIndexOfRange(o, es, offset, offset + size);
1276 return (i == -1) ? -1 : i - offset;
1277 }
1278
1279 public boolean contains(Object o) {
1280 return indexOf(o) >= 0;
1281 }
1282
1283 public boolean containsAll(Collection<?> c) {
1284 final Object[] es;
1285 final int offset;
1286 final int size;
1287 synchronized (lock) {
1288 es = getArrayChecked();
1289 offset = this.offset;
1290 size = this.size;
1291 }
1292 for (Object o : c)
1293 if (indexOfRange(o, es, offset, offset + size) < 0)
1294 return false;
1295 return true;
1296 }
1297
1298 public boolean isEmpty() {
1299 return size() == 0;
1300 }
1301
1302 public String toString() {
1303 return Arrays.toString(toArray());
1304 }
1305
1306 public int hashCode() {
1307 final Object[] es;
1308 final int offset;
1309 final int size;
1310 synchronized (lock) {
1311 es = getArrayChecked();
1312 offset = this.offset;
1313 size = this.size;
1314 }
1315 return hashCodeOfRange(es, offset, offset + size);
1316 }
1317
1318 public boolean equals(Object o) {
1319 if (o == this)
1320 return true;
1321 if (!(o instanceof List))
1322 return false;
1323 Iterator<?> it = ((List<?>)o).iterator();
1324
1325 final Object[] es;
1326 final int offset;
1327 final int size;
1328 synchronized (lock) {
1329 es = getArrayChecked();
1330 offset = this.offset;
1331 size = this.size;
1332 }
1333
1334 for (int i = offset, end = offset + size; i < end; i++)
1335 if (!it.hasNext() || !Objects.equals(es[i], it.next()))
1336 return false;
1337 return !it.hasNext();
1338 }
1339
1340 public E set(int index, E element) {
1341 synchronized (lock) {
1342 rangeCheck(index);
1343 checkForComodification();
1344 E x = CopyOnWriteArrayList.this.set(offset + index, element);
1345 expectedArray = getArray();
1346 return x;
1347 }
1348 }
1349
1350 public E get(int index) {
1351 synchronized (lock) {
1352 rangeCheck(index);
1353 checkForComodification();
1354 return CopyOnWriteArrayList.this.get(offset + index);
1355 }
1356 }
1357
1358 public int size() {
1359 synchronized (lock) {
1360 checkForComodification();
1361 return size;
1362 }
1363 }
1364
1365 public boolean add(E element) {
1366 synchronized (lock) {
1367 checkForComodification();
1368 CopyOnWriteArrayList.this.add(offset + size, element);
1369 expectedArray = getArray();
1370 size++;
1371 }
1372 return true;
1373 }
1374
1375 public void add(int index, E element) {
1376 synchronized (lock) {
1377 checkForComodification();
1378 rangeCheckForAdd(index);
1379 CopyOnWriteArrayList.this.add(offset + index, element);
1380 expectedArray = getArray();
1381 size++;
1382 }
1383 }
1384
1385 public boolean addAll(Collection<? extends E> c) {
1386 synchronized (lock) {
1387 final Object[] oldArray = getArrayChecked();
1388 boolean modified =
1389 CopyOnWriteArrayList.this.addAll(offset + size, c);
1390 size += (expectedArray = getArray()).length - oldArray.length;
1391 return modified;
1392 }
1393 }
1394
1395 public boolean addAll(int index, Collection<? extends E> c) {
1396 synchronized (lock) {
1397 rangeCheckForAdd(index);
1398 final Object[] oldArray = getArrayChecked();
1399 boolean modified =
1400 CopyOnWriteArrayList.this.addAll(offset + index, c);
1401 size += (expectedArray = getArray()).length - oldArray.length;
1402 return modified;
1403 }
1404 }
1405
1406 public void clear() {
1407 synchronized (lock) {
1408 checkForComodification();
1409 removeRange(offset, offset + size);
1410 expectedArray = getArray();
1411 size = 0;
1412 }
1413 }
1414
1415 public E remove(int index) {
1416 synchronized (lock) {
1417 rangeCheck(index);
1418 checkForComodification();
1419 E result = CopyOnWriteArrayList.this.remove(offset + index);
1420 expectedArray = getArray();
1421 size--;
1422 return result;
1423 }
1424 }
1425
1426 public boolean remove(Object o) {
1427 synchronized (lock) {
1428 checkForComodification();
1429 int index = indexOf(o);
1430 if (index == -1)
1431 return false;
1432 remove(index);
1433 return true;
1434 }
1435 }
1436
1437 public Iterator<E> iterator() {
1438 return listIterator(0);
1439 }
1440
1441 public ListIterator<E> listIterator() {
1442 return listIterator(0);
1443 }
1444
1445 public ListIterator<E> listIterator(int index) {
1446 synchronized (lock) {
1447 checkForComodification();
1448 rangeCheckForAdd(index);
1449 return new COWSubListIterator<E>(
1450 CopyOnWriteArrayList.this, index, offset, size);
1451 }
1452 }
1453
1454 public List<E> subList(int fromIndex, int toIndex) {
1455 synchronized (lock) {
1456 checkForComodification();
1457 if (fromIndex < 0 || toIndex > size || fromIndex > toIndex)
1458 throw new IndexOutOfBoundsException();
1459 return new COWSubList(expectedArray, fromIndex + offset, toIndex - fromIndex);
1460 }
1461 }
1462
1463 public void forEach(Consumer<? super E> action) {
1464 Objects.requireNonNull(action);
1465 int i, end; final Object[] es;
1466 synchronized (lock) {
1467 es = getArrayChecked();
1468 i = offset;
1469 end = i + size;
1470 }
1471 for (; i < end; i++)
1472 action.accept(elementAt(es, i));
1473 }
1474
1475 public void replaceAll(UnaryOperator<E> operator) {
1476 synchronized (lock) {
1477 checkForComodification();
1478 replaceAllRange(operator, offset, offset + size);
1479 expectedArray = getArray();
1480 }
1481 }
1482
1483 public void sort(Comparator<? super E> c) {
1484 synchronized (lock) {
1485 checkForComodification();
1486 sortRange(c, offset, offset + size);
1487 expectedArray = getArray();
1488 }
1489 }
1490
1491 public boolean removeAll(Collection<?> c) {
1492 Objects.requireNonNull(c);
1493 return bulkRemove(e -> c.contains(e));
1494 }
1495
1496 public boolean retainAll(Collection<?> c) {
1497 Objects.requireNonNull(c);
1498 return bulkRemove(e -> !c.contains(e));
1499 }
1500
1501 public boolean removeIf(Predicate<? super E> filter) {
1502 Objects.requireNonNull(filter);
1503 return bulkRemove(filter);
1504 }
1505
1506 private boolean bulkRemove(Predicate<? super E> filter) {
1507 synchronized (lock) {
1508 final Object[] oldArray = getArrayChecked();
1509 boolean modified = CopyOnWriteArrayList.this.bulkRemove(
1510 filter, offset, offset + size);
1511 size += (expectedArray = getArray()).length - oldArray.length;
1512 return modified;
1513 }
1514 }
1515
1516 public Spliterator<E> spliterator() {
1517 synchronized (lock) {
1518 return Spliterators.spliterator(
1519 getArrayChecked(), offset, offset + size,
1520 Spliterator.IMMUTABLE | Spliterator.ORDERED);
1521 }
1522 }
1523
1524 }
1525
1526 private static class COWSubListIterator<E> implements ListIterator<E> {
1527 private final ListIterator<E> it;
1528 private final int offset;
1529 private final int size;
1530
1531 COWSubListIterator(List<E> l, int index, int offset, int size) {
1532 this.offset = offset;
1533 this.size = size;
1534 it = l.listIterator(index + offset);
1535 }
1536
1537 public boolean hasNext() {
1538 return nextIndex() < size;
1539 }
1540
1541 public E next() {
1542 if (hasNext())
1543 return it.next();
1544 else
1545 throw new NoSuchElementException();
1546 }
1547
1548 public boolean hasPrevious() {
1549 return previousIndex() >= 0;
1550 }
1551
1552 public E previous() {
1553 if (hasPrevious())
1554 return it.previous();
1555 else
1556 throw new NoSuchElementException();
1557 }
1558
1559 public int nextIndex() {
1560 return it.nextIndex() - offset;
1561 }
1562
1563 public int previousIndex() {
1564 return it.previousIndex() - offset;
1565 }
1566
1567 public void remove() {
1568 throw new UnsupportedOperationException();
1569 }
1570
1571 public void set(E e) {
1572 throw new UnsupportedOperationException();
1573 }
1574
1575 public void add(E e) {
1576 throw new UnsupportedOperationException();
1577 }
1578
1579 @Override
1580 @SuppressWarnings("unchecked")
1581 public void forEachRemaining(Consumer<? super E> action) {
1582 Objects.requireNonNull(action);
1583 while (hasNext()) {
1584 action.accept(it.next());
1585 }
1586 }
1587 }
1588
1589 /** Initializes the lock; for use when deserializing or cloning. */
1590 private void resetLock() {
1591 Field lockField = java.security.AccessController.doPrivileged(
1592 (java.security.PrivilegedAction<Field>) () -> {
1593 try {
1594 Field f = CopyOnWriteArrayList.class
1595 .getDeclaredField("lock");
1596 f.setAccessible(true);
1597 return f;
1598 } catch (ReflectiveOperationException e) {
1599 throw new Error(e);
1600 }});
1601 try {
1602 lockField.set(this, new Object());
1603 } catch (IllegalAccessException e) {
1604 throw new Error(e);
1605 }
1606 }
1607 }