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 import java.util.AbstractList;
37 import java.util.Arrays;
38 import java.util.Collection;
39 import java.util.Comparator;
40 import java.util.ConcurrentModificationException;
41 import java.util.Iterator;
42 import java.util.List;
43 import java.util.ListIterator;
44 import java.util.NoSuchElementException;
45 import java.util.Objects;
46 import java.util.RandomAccess;
47 import java.util.Spliterator;
48 import java.util.Spliterators;
49 import java.util.concurrent.locks.ReentrantLock;
50 import java.util.function.Consumer;
51 import java.util.function.Predicate;
52 import java.util.function.UnaryOperator;
53
54 /**
55 * A thread-safe variant of {@link java.util.ArrayList} in which all mutative
56 * operations ({@code add}, {@code set}, and so on) are implemented by
57 * making a fresh copy of the underlying array.
58 *
59 * <p>This is ordinarily too costly, but may be <em>more</em> efficient
60 * than alternatives when traversal operations vastly outnumber
61 * mutations, and is useful when you cannot or don't want to
62 * synchronize traversals, yet need to preclude interference among
63 * concurrent threads. The "snapshot" style iterator method uses a
64 * reference to the state of the array at the point that the iterator
65 * was created. This array never changes during the lifetime of the
66 * iterator, so interference is impossible and the iterator is
67 * guaranteed not to throw {@code ConcurrentModificationException}.
68 * The iterator will not reflect additions, removals, or changes to
69 * the list since the iterator was created. Element-changing
70 * operations on iterators themselves ({@code remove}, {@code set}, and
71 * {@code add}) are not supported. These methods throw
72 * {@code UnsupportedOperationException}.
73 *
74 * <p>All elements are permitted, including {@code null}.
75 *
76 * <p>Memory consistency effects: As with other concurrent
77 * collections, actions in a thread prior to placing an object into a
78 * {@code CopyOnWriteArrayList}
79 * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
80 * actions subsequent to the access or removal of that element from
81 * the {@code CopyOnWriteArrayList} in another thread.
82 *
83 * <p>This class is a member of the
84 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
85 * Java Collections Framework</a>.
86 *
87 * @since 1.5
88 * @author Doug Lea
89 * @param <E> the type of elements held in this collection
90 */
91 public class CopyOnWriteArrayList<E>
92 implements List<E>, RandomAccess, Cloneable, java.io.Serializable {
93 private static final long serialVersionUID = 8673264195747942595L;
94
95 /** The lock protecting all mutators */
96 final transient ReentrantLock lock = new ReentrantLock();
97
98 /** The array, accessed only via getArray/setArray. */
99 private transient volatile Object[] array;
100
101 /**
102 * Gets the array. Non-private so as to also be accessible
103 * from CopyOnWriteArraySet class.
104 */
105 final Object[] getArray() {
106 return array;
107 }
108
109 /**
110 * Sets the array.
111 */
112 final void setArray(Object[] a) {
113 array = a;
114 }
115
116 /**
117 * Creates an empty list.
118 */
119 public CopyOnWriteArrayList() {
120 setArray(new Object[0]);
121 }
122
123 /**
124 * Creates a list containing the elements of the specified
125 * collection, in the order they are returned by the collection's
126 * iterator.
127 *
128 * @param c the collection of initially held elements
129 * @throws NullPointerException if the specified collection is null
130 */
131 public CopyOnWriteArrayList(Collection<? extends E> c) {
132 Object[] elements;
133 if (c.getClass() == CopyOnWriteArrayList.class)
134 elements = ((CopyOnWriteArrayList<?>)c).getArray();
135 else {
136 elements = c.toArray();
137 // defend against c.toArray (incorrectly) not returning Object[]
138 // (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652)
139 if (elements.getClass() != Object[].class)
140 elements = Arrays.copyOf(elements, elements.length, Object[].class);
141 }
142 setArray(elements);
143 }
144
145 /**
146 * Creates a list holding a copy of the given array.
147 *
148 * @param toCopyIn the array (a copy of this array is used as the
149 * internal array)
150 * @throws NullPointerException if the specified array is null
151 */
152 public CopyOnWriteArrayList(E[] toCopyIn) {
153 setArray(Arrays.copyOf(toCopyIn, toCopyIn.length, Object[].class));
154 }
155
156 /**
157 * Returns the number of elements in this list.
158 *
159 * @return the number of elements in this list
160 */
161 public int size() {
162 return getArray().length;
163 }
164
165 /**
166 * Returns {@code true} if this list contains no elements.
167 *
168 * @return {@code true} if this list contains no elements
169 */
170 public boolean isEmpty() {
171 return size() == 0;
172 }
173
174 /**
175 * Tests for equality, coping with nulls.
176 */
177 private static boolean eq(Object o1, Object o2) {
178 return (o1 == null) ? o2 == null : o1.equals(o2);
179 }
180
181 /**
182 * static version of indexOf, to allow repeated calls without
183 * needing to re-acquire array each time.
184 * @param o element to search for
185 * @param elements the array
186 * @param index first index to search
187 * @param fence one past last index to search
188 * @return index of element, or -1 if absent
189 */
190 private static int indexOf(Object o, Object[] elements,
191 int index, int fence) {
192 if (o == null) {
193 for (int i = index; i < fence; i++)
194 if (elements[i] == null)
195 return i;
196 } else {
197 for (int i = index; i < fence; i++)
198 if (o.equals(elements[i]))
199 return i;
200 }
201 return -1;
202 }
203
204 /**
205 * static version of lastIndexOf.
206 * @param o element to search for
207 * @param elements the array
208 * @param index first index to search
209 * @return index of element, or -1 if absent
210 */
211 private static int lastIndexOf(Object o, Object[] elements, int index) {
212 if (o == null) {
213 for (int i = index; i >= 0; i--)
214 if (elements[i] == null)
215 return i;
216 } else {
217 for (int i = index; i >= 0; i--)
218 if (o.equals(elements[i]))
219 return i;
220 }
221 return -1;
222 }
223
224 /**
225 * Returns {@code true} if this list contains the specified element.
226 * More formally, returns {@code true} if and only if this list contains
227 * at least one element {@code e} such that
228 * <tt>(o==null ? e==null : o.equals(e))</tt>.
229 *
230 * @param o element whose presence in this list is to be tested
231 * @return {@code true} if this list contains the specified element
232 */
233 public boolean contains(Object o) {
234 Object[] elements = getArray();
235 return indexOf(o, elements, 0, elements.length) >= 0;
236 }
237
238 /**
239 * {@inheritDoc}
240 */
241 public int indexOf(Object o) {
242 Object[] elements = getArray();
243 return indexOf(o, elements, 0, elements.length);
244 }
245
246 /**
247 * Returns the index of the first occurrence of the specified element in
248 * this list, searching forwards from {@code index}, or returns -1 if
249 * the element is not found.
250 * More formally, returns the lowest index {@code i} such that
251 * <tt>(i >= index && (e==null ? get(i)==null : e.equals(get(i))))</tt>,
252 * or -1 if there is no such index.
253 *
254 * @param e element to search for
255 * @param index index to start searching from
256 * @return the index of the first occurrence of the element in
257 * this list at position {@code index} or later in the list;
258 * {@code -1} if the element is not found.
259 * @throws IndexOutOfBoundsException if the specified index is negative
260 */
261 public int indexOf(E e, int index) {
262 Object[] elements = getArray();
263 return indexOf(e, elements, index, elements.length);
264 }
265
266 /**
267 * {@inheritDoc}
268 */
269 public int lastIndexOf(Object o) {
270 Object[] elements = getArray();
271 return lastIndexOf(o, elements, elements.length - 1);
272 }
273
274 /**
275 * Returns the index of the last occurrence of the specified element in
276 * this list, searching backwards from {@code index}, or returns -1 if
277 * the element is not found.
278 * More formally, returns the highest index {@code i} such that
279 * <tt>(i <= index && (e==null ? get(i)==null : e.equals(get(i))))</tt>,
280 * or -1 if there is no such index.
281 *
282 * @param e element to search for
283 * @param index index to start searching backwards from
284 * @return the index of the last occurrence of the element at position
285 * less than or equal to {@code index} in this list;
286 * -1 if the element is not found.
287 * @throws IndexOutOfBoundsException if the specified index is greater
288 * than or equal to the current size of this list
289 */
290 public int lastIndexOf(E e, int index) {
291 Object[] elements = getArray();
292 return lastIndexOf(e, elements, index);
293 }
294
295 /**
296 * Returns a shallow copy of this list. (The elements themselves
297 * are not copied.)
298 *
299 * @return a clone of this list
300 */
301 public Object clone() {
302 try {
303 @SuppressWarnings("unchecked")
304 CopyOnWriteArrayList<E> clone =
305 (CopyOnWriteArrayList<E>) super.clone();
306 clone.resetLock();
307 return clone;
308 } catch (CloneNotSupportedException e) {
309 // this shouldn't happen, since we are Cloneable
310 throw new InternalError();
311 }
312 }
313
314 /**
315 * Returns an array containing all of the elements in this list
316 * in proper sequence (from first to last element).
317 *
318 * <p>The returned array will be "safe" in that no references to it are
319 * maintained by this list. (In other words, this method must allocate
320 * a new array). The caller is thus free to modify the returned array.
321 *
322 * <p>This method acts as bridge between array-based and collection-based
323 * APIs.
324 *
325 * @return an array containing all the elements in this list
326 */
327 public Object[] toArray() {
328 Object[] elements = getArray();
329 return Arrays.copyOf(elements, elements.length);
330 }
331
332 /**
333 * Returns an array containing all of the elements in this list in
334 * proper sequence (from first to last element); the runtime type of
335 * the returned array is that of the specified array. If the list fits
336 * in the specified array, it is returned therein. Otherwise, a new
337 * array is allocated with the runtime type of the specified array and
338 * the size of this list.
339 *
340 * <p>If this list fits in the specified array with room to spare
341 * (i.e., the array has more elements than this list), the element in
342 * the array immediately following the end of the list is set to
343 * {@code null}. (This is useful in determining the length of this
344 * list <i>only</i> if the caller knows that this list does not contain
345 * any null elements.)
346 *
347 * <p>Like the {@link #toArray()} method, this method acts as bridge between
348 * array-based and collection-based APIs. Further, this method allows
349 * precise control over the runtime type of the output array, and may,
350 * under certain circumstances, be used to save allocation costs.
351 *
352 * <p>Suppose {@code x} is a list known to contain only strings.
353 * The following code can be used to dump the list into a newly
354 * allocated array of {@code String}:
355 *
356 * <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
357 *
358 * Note that {@code toArray(new Object[0])} is identical in function to
359 * {@code toArray()}.
360 *
361 * @param a the array into which the elements of the list are to
362 * be stored, if it is big enough; otherwise, a new array of the
363 * same runtime type is allocated for this purpose.
364 * @return an array containing all the elements in this list
365 * @throws ArrayStoreException if the runtime type of the specified array
366 * is not a supertype of the runtime type of every element in
367 * this list
368 * @throws NullPointerException if the specified array is null
369 */
370 @SuppressWarnings("unchecked")
371 public <T> T[] toArray(T a[]) {
372 Object[] elements = getArray();
373 int len = elements.length;
374 if (a.length < len)
375 return (T[]) Arrays.copyOf(elements, len, a.getClass());
376 else {
377 System.arraycopy(elements, 0, a, 0, len);
378 if (a.length > len)
379 a[len] = null;
380 return a;
381 }
382 }
383
384 // Positional Access Operations
385
386 @SuppressWarnings("unchecked")
387 private E get(Object[] a, int index) {
388 return (E) a[index];
389 }
390
391 /**
392 * {@inheritDoc}
393 *
394 * @throws IndexOutOfBoundsException {@inheritDoc}
395 */
396 public E get(int index) {
397 return get(getArray(), index);
398 }
399
400 /**
401 * Replaces the element at the specified position in this list with the
402 * specified element.
403 *
404 * @throws IndexOutOfBoundsException {@inheritDoc}
405 */
406 public E set(int index, E element) {
407 final ReentrantLock lock = this.lock;
408 lock.lock();
409 try {
410 Object[] elements = getArray();
411 E oldValue = get(elements, index);
412
413 if (oldValue != element) {
414 int len = elements.length;
415 Object[] newElements = Arrays.copyOf(elements, len);
416 newElements[index] = element;
417 setArray(newElements);
418 } else {
419 // Not quite a no-op; ensures volatile write semantics
420 setArray(elements);
421 }
422 return oldValue;
423 } finally {
424 lock.unlock();
425 }
426 }
427
428 /**
429 * Appends the specified element to the end of this list.
430 *
431 * @param e element to be appended to this list
432 * @return {@code true} (as specified by {@link Collection#add})
433 */
434 public boolean add(E e) {
435 final ReentrantLock lock = this.lock;
436 lock.lock();
437 try {
438 Object[] elements = getArray();
439 int len = elements.length;
440 Object[] newElements = Arrays.copyOf(elements, len + 1);
441 newElements[len] = e;
442 setArray(newElements);
443 return true;
444 } finally {
445 lock.unlock();
446 }
447 }
448
449 /**
450 * Inserts the specified element at the specified position in this
451 * list. Shifts the element currently at that position (if any) and
452 * any subsequent elements to the right (adds one to their indices).
453 *
454 * @throws IndexOutOfBoundsException {@inheritDoc}
455 */
456 public void add(int index, E element) {
457 final ReentrantLock lock = this.lock;
458 lock.lock();
459 try {
460 Object[] elements = getArray();
461 int len = elements.length;
462 if (index > len || index < 0)
463 throw new IndexOutOfBoundsException("Index: "+index+
464 ", Size: "+len);
465 Object[] newElements;
466 int numMoved = len - index;
467 if (numMoved == 0)
468 newElements = Arrays.copyOf(elements, len + 1);
469 else {
470 newElements = new Object[len + 1];
471 System.arraycopy(elements, 0, newElements, 0, index);
472 System.arraycopy(elements, index, newElements, index + 1,
473 numMoved);
474 }
475 newElements[index] = element;
476 setArray(newElements);
477 } finally {
478 lock.unlock();
479 }
480 }
481
482 /**
483 * Removes the element at the specified position in this list.
484 * Shifts any subsequent elements to the left (subtracts one from their
485 * indices). Returns the element that was removed from the list.
486 *
487 * @throws IndexOutOfBoundsException {@inheritDoc}
488 */
489 public E remove(int index) {
490 final ReentrantLock lock = this.lock;
491 lock.lock();
492 try {
493 Object[] elements = getArray();
494 int len = elements.length;
495 E oldValue = get(elements, index);
496 int numMoved = len - index - 1;
497 if (numMoved == 0)
498 setArray(Arrays.copyOf(elements, len - 1));
499 else {
500 Object[] newElements = new Object[len - 1];
501 System.arraycopy(elements, 0, newElements, 0, index);
502 System.arraycopy(elements, index + 1, newElements, index,
503 numMoved);
504 setArray(newElements);
505 }
506 return oldValue;
507 } finally {
508 lock.unlock();
509 }
510 }
511
512 /**
513 * Removes the first occurrence of the specified element from this list,
514 * if it is present. If this list does not contain the element, it is
515 * unchanged. More formally, removes the element with the lowest index
516 * {@code i} such that
517 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>
518 * (if such an element exists). Returns {@code true} if this list
519 * contained the specified element (or equivalently, if this list
520 * changed as a result of the call).
521 *
522 * @param o element to be removed from this list, if present
523 * @return {@code true} if this list contained the specified element
524 */
525 public boolean remove(Object o) {
526 Object[] snapshot = getArray();
527 int index = indexOf(o, snapshot, 0, snapshot.length);
528 return (index < 0) ? false : remove(o, snapshot, index);
529 }
530
531 /**
532 * A version of remove(Object) using the strong hint that given
533 * recent snapshot contains o at the given index.
534 */
535 private boolean remove(Object o, Object[] snapshot, int index) {
536 final ReentrantLock lock = this.lock;
537 lock.lock();
538 try {
539 Object[] current = getArray();
540 int len = current.length;
541 if (snapshot != current) findIndex: {
542 int prefix = Math.min(index, len);
543 for (int i = 0; i < prefix; i++) {
544 if (current[i] != snapshot[i] && eq(o, current[i])) {
545 index = i;
546 break findIndex;
547 }
548 }
549 if (index >= len)
550 return false;
551 if (current[index] == o)
552 break findIndex;
553 index = indexOf(o, current, index, len);
554 if (index < 0)
555 return false;
556 }
557 Object[] newElements = new Object[len - 1];
558 System.arraycopy(current, 0, newElements, 0, index);
559 System.arraycopy(current, index + 1,
560 newElements, index,
561 len - index - 1);
562 setArray(newElements);
563 return true;
564 } finally {
565 lock.unlock();
566 }
567 }
568
569 /**
570 * Removes from this list all of the elements whose index is between
571 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
572 * Shifts any succeeding elements to the left (reduces their index).
573 * This call shortens the list by {@code (toIndex - fromIndex)} elements.
574 * (If {@code toIndex==fromIndex}, this operation has no effect.)
575 *
576 * @param fromIndex index of first element to be removed
577 * @param toIndex index after last element to be removed
578 * @throws IndexOutOfBoundsException if fromIndex or toIndex out of range
579 * ({@code fromIndex < 0 || toIndex > size() || toIndex < fromIndex})
580 */
581 void removeRange(int fromIndex, int toIndex) {
582 final ReentrantLock lock = this.lock;
583 lock.lock();
584 try {
585 Object[] elements = getArray();
586 int len = elements.length;
587
588 if (fromIndex < 0 || toIndex > len || toIndex < fromIndex)
589 throw new IndexOutOfBoundsException();
590 int newlen = len - (toIndex - fromIndex);
591 int numMoved = len - toIndex;
592 if (numMoved == 0)
593 setArray(Arrays.copyOf(elements, newlen));
594 else {
595 Object[] newElements = new Object[newlen];
596 System.arraycopy(elements, 0, newElements, 0, fromIndex);
597 System.arraycopy(elements, toIndex, newElements,
598 fromIndex, numMoved);
599 setArray(newElements);
600 }
601 } finally {
602 lock.unlock();
603 }
604 }
605
606 /**
607 * Appends the element, if not present.
608 *
609 * @param e element to be added to this list, if absent
610 * @return {@code true} if the element was added
611 */
612 public boolean addIfAbsent(E e) {
613 Object[] snapshot = getArray();
614 return indexOf(e, snapshot, 0, snapshot.length) >= 0 ? false :
615 addIfAbsent(e, snapshot);
616 }
617
618 /**
619 * A version of addIfAbsent using the strong hint that given
620 * recent snapshot does not contain e.
621 */
622 private boolean addIfAbsent(E e, Object[] snapshot) {
623 final ReentrantLock lock = this.lock;
624 lock.lock();
625 try {
626 Object[] current = getArray();
627 int len = current.length;
628 if (snapshot != current) {
629 // Optimize for lost race to another addXXX operation
630 int common = Math.min(snapshot.length, len);
631 for (int i = 0; i < common; i++)
632 if (current[i] != snapshot[i] && eq(e, current[i]))
633 return false;
634 if (indexOf(e, current, common, len) >= 0)
635 return false;
636 }
637 Object[] newElements = Arrays.copyOf(current, len + 1);
638 newElements[len] = e;
639 setArray(newElements);
640 return true;
641 } finally {
642 lock.unlock();
643 }
644 }
645
646 /**
647 * Returns {@code true} if this list contains all of the elements of the
648 * specified collection.
649 *
650 * @param c collection to be checked for containment in this list
651 * @return {@code true} if this list contains all of the elements of the
652 * specified collection
653 * @throws NullPointerException if the specified collection is null
654 * @see #contains(Object)
655 */
656 public boolean containsAll(Collection<?> c) {
657 Object[] elements = getArray();
658 int len = elements.length;
659 for (Object e : c) {
660 if (indexOf(e, elements, 0, len) < 0)
661 return false;
662 }
663 return true;
664 }
665
666 /**
667 * Removes from this list all of its elements that are contained in
668 * the specified collection. This is a particularly expensive operation
669 * in this class because of the need for an internal temporary array.
670 *
671 * @param c collection containing elements to be removed from this list
672 * @return {@code true} if this list changed as a result of the call
673 * @throws ClassCastException if the class of an element of this list
674 * is incompatible with the specified collection
675 * (<a href="../Collection.html#optional-restrictions">optional</a>)
676 * @throws NullPointerException if this list contains a null element and the
677 * specified collection does not permit null elements
678 * (<a href="../Collection.html#optional-restrictions">optional</a>),
679 * or if the specified collection is null
680 * @see #remove(Object)
681 */
682 public boolean removeAll(Collection<?> c) {
683 if (c == null) throw new NullPointerException();
684 final ReentrantLock lock = this.lock;
685 lock.lock();
686 try {
687 Object[] elements = getArray();
688 int len = elements.length;
689 if (len != 0) {
690 // temp array holds those elements we know we want to keep
691 int newlen = 0;
692 Object[] temp = new Object[len];
693 for (int i = 0; i < len; ++i) {
694 Object element = elements[i];
695 if (!c.contains(element))
696 temp[newlen++] = element;
697 }
698 if (newlen != len) {
699 setArray(Arrays.copyOf(temp, newlen));
700 return true;
701 }
702 }
703 return false;
704 } finally {
705 lock.unlock();
706 }
707 }
708
709 /**
710 * Retains only the elements in this list that are contained in the
711 * specified collection. In other words, removes from this list all of
712 * its elements that are not contained in the specified collection.
713 *
714 * @param c collection containing elements to be retained in this list
715 * @return {@code true} if this list changed as a result of the call
716 * @throws ClassCastException if the class of an element of this list
717 * is incompatible with the specified collection
718 * (<a href="../Collection.html#optional-restrictions">optional</a>)
719 * @throws NullPointerException if this list contains a null element and the
720 * specified collection does not permit null elements
721 * (<a href="../Collection.html#optional-restrictions">optional</a>),
722 * or if the specified collection is null
723 * @see #remove(Object)
724 */
725 public boolean retainAll(Collection<?> c) {
726 if (c == null) throw new NullPointerException();
727 final ReentrantLock lock = this.lock;
728 lock.lock();
729 try {
730 Object[] elements = getArray();
731 int len = elements.length;
732 if (len != 0) {
733 // temp array holds those elements we know we want to keep
734 int newlen = 0;
735 Object[] temp = new Object[len];
736 for (int i = 0; i < len; ++i) {
737 Object element = elements[i];
738 if (c.contains(element))
739 temp[newlen++] = element;
740 }
741 if (newlen != len) {
742 setArray(Arrays.copyOf(temp, newlen));
743 return true;
744 }
745 }
746 return false;
747 } finally {
748 lock.unlock();
749 }
750 }
751
752 /**
753 * Appends all of the elements in the specified collection that
754 * are not already contained in this list, to the end of
755 * this list, in the order that they are returned by the
756 * specified collection's iterator.
757 *
758 * @param c collection containing elements to be added to this list
759 * @return the number of elements added
760 * @throws NullPointerException if the specified collection is null
761 * @see #addIfAbsent(Object)
762 */
763 public int addAllAbsent(Collection<? extends E> c) {
764 Object[] cs = c.toArray();
765 if (cs.length == 0)
766 return 0;
767 final ReentrantLock lock = this.lock;
768 lock.lock();
769 try {
770 Object[] elements = getArray();
771 int len = elements.length;
772 int added = 0;
773 // uniquify and compact elements in cs
774 for (int i = 0; i < cs.length; ++i) {
775 Object e = cs[i];
776 if (indexOf(e, elements, 0, len) < 0 &&
777 indexOf(e, cs, 0, added) < 0)
778 cs[added++] = e;
779 }
780 if (added > 0) {
781 Object[] newElements = Arrays.copyOf(elements, len + added);
782 System.arraycopy(cs, 0, newElements, len, added);
783 setArray(newElements);
784 }
785 return added;
786 } finally {
787 lock.unlock();
788 }
789 }
790
791 /**
792 * Removes all of the elements from this list.
793 * The list will be empty after this call returns.
794 */
795 public void clear() {
796 final ReentrantLock lock = this.lock;
797 lock.lock();
798 try {
799 setArray(new Object[0]);
800 } finally {
801 lock.unlock();
802 }
803 }
804
805 /**
806 * Appends all of the elements in the specified collection to the end
807 * of this list, in the order that they are returned by the specified
808 * collection's iterator.
809 *
810 * @param c collection containing elements to be added to this list
811 * @return {@code true} if this list changed as a result of the call
812 * @throws NullPointerException if the specified collection is null
813 * @see #add(Object)
814 */
815 public boolean addAll(Collection<? extends E> c) {
816 Object[] cs = (c.getClass() == CopyOnWriteArrayList.class) ?
817 ((CopyOnWriteArrayList<?>)c).getArray() : c.toArray();
818 if (cs.length == 0)
819 return false;
820 final ReentrantLock lock = this.lock;
821 lock.lock();
822 try {
823 Object[] elements = getArray();
824 int len = elements.length;
825 if (len == 0 && cs.getClass() == Object[].class)
826 setArray(cs);
827 else {
828 Object[] newElements = Arrays.copyOf(elements, len + cs.length);
829 System.arraycopy(cs, 0, newElements, len, cs.length);
830 setArray(newElements);
831 }
832 return true;
833 } finally {
834 lock.unlock();
835 }
836 }
837
838 /**
839 * Inserts all of the elements in the specified collection into this
840 * list, starting at the specified position. Shifts the element
841 * currently at that position (if any) and any subsequent elements to
842 * the right (increases their indices). The new elements will appear
843 * in this list in the order that they are returned by the
844 * specified collection's iterator.
845 *
846 * @param index index at which to insert the first element
847 * from the specified collection
848 * @param c collection containing elements to be added to this list
849 * @return {@code true} if this list changed as a result of the call
850 * @throws IndexOutOfBoundsException {@inheritDoc}
851 * @throws NullPointerException if the specified collection is null
852 * @see #add(int,Object)
853 */
854 public boolean addAll(int index, Collection<? extends E> c) {
855 Object[] cs = c.toArray();
856 final ReentrantLock lock = this.lock;
857 lock.lock();
858 try {
859 Object[] elements = getArray();
860 int len = elements.length;
861 if (index > len || index < 0)
862 throw new IndexOutOfBoundsException("Index: "+index+
863 ", Size: "+len);
864 if (cs.length == 0)
865 return false;
866 int numMoved = len - index;
867 Object[] newElements;
868 if (numMoved == 0)
869 newElements = Arrays.copyOf(elements, len + cs.length);
870 else {
871 newElements = new Object[len + cs.length];
872 System.arraycopy(elements, 0, newElements, 0, index);
873 System.arraycopy(elements, index,
874 newElements, index + cs.length,
875 numMoved);
876 }
877 System.arraycopy(cs, 0, newElements, index, cs.length);
878 setArray(newElements);
879 return true;
880 } finally {
881 lock.unlock();
882 }
883 }
884
885 public void forEach(Consumer<? super E> action) {
886 if (action == null) throw new NullPointerException();
887 Object[] elements = getArray();
888 int len = elements.length;
889 for (int i = 0; i < len; ++i) {
890 @SuppressWarnings("unchecked") E e = (E) elements[i];
891 action.accept(e);
892 }
893 }
894
895 public boolean removeIf(Predicate<? super E> filter) {
896 if (filter == null) throw new NullPointerException();
897 final ReentrantLock lock = this.lock;
898 lock.lock();
899 try {
900 Object[] elements = getArray();
901 int len = elements.length;
902 if (len != 0) {
903 int newlen = 0;
904 Object[] temp = new Object[len];
905 for (int i = 0; i < len; ++i) {
906 @SuppressWarnings("unchecked") E e = (E) elements[i];
907 if (!filter.test(e))
908 temp[newlen++] = e;
909 }
910 if (newlen != len) {
911 setArray(Arrays.copyOf(temp, newlen));
912 return true;
913 }
914 }
915 return false;
916 } finally {
917 lock.unlock();
918 }
919 }
920
921 public void replaceAll(UnaryOperator<E> operator) {
922 if (operator == null) throw new NullPointerException();
923 final ReentrantLock lock = this.lock;
924 lock.lock();
925 try {
926 Object[] elements = getArray();
927 int len = elements.length;
928 Object[] newElements = Arrays.copyOf(elements, len);
929 for (int i = 0; i < len; ++i) {
930 @SuppressWarnings("unchecked") E e = (E) elements[i];
931 newElements[i] = operator.apply(e);
932 }
933 setArray(newElements);
934 } finally {
935 lock.unlock();
936 }
937 }
938
939 public void sort(Comparator<? super E> c) {
940 final ReentrantLock lock = this.lock;
941 lock.lock();
942 try {
943 Object[] elements = getArray();
944 Object[] newElements = Arrays.copyOf(elements, elements.length);
945 @SuppressWarnings("unchecked") E[] es = (E[])newElements;
946 Arrays.sort(es, c);
947 setArray(newElements);
948 } finally {
949 lock.unlock();
950 }
951 }
952
953 /**
954 * Saves this list to a stream (that is, serializes it).
955 *
956 * @param s the stream
957 * @throws java.io.IOException if an I/O error occurs
958 * @serialData The length of the array backing the list is emitted
959 * (int), followed by all of its elements (each an Object)
960 * in the proper order.
961 */
962 private void writeObject(java.io.ObjectOutputStream s)
963 throws java.io.IOException {
964
965 s.defaultWriteObject();
966
967 Object[] elements = getArray();
968 // Write out array length
969 s.writeInt(elements.length);
970
971 // Write out all elements in the proper order.
972 for (Object element : elements)
973 s.writeObject(element);
974 }
975
976 /**
977 * Reconstitutes this list from a stream (that is, deserializes it).
978 * @param s the stream
979 * @throws ClassNotFoundException if the class of a serialized object
980 * could not be found
981 * @throws java.io.IOException if an I/O error occurs
982 */
983 private void readObject(java.io.ObjectInputStream s)
984 throws java.io.IOException, ClassNotFoundException {
985
986 s.defaultReadObject();
987
988 // bind to new lock
989 resetLock();
990
991 // Read in array length and allocate array
992 int len = s.readInt();
993 Object[] elements = new Object[len];
994
995 // Read in all elements in the proper order.
996 for (int i = 0; i < len; i++)
997 elements[i] = s.readObject();
998 setArray(elements);
999 }
1000
1001 /**
1002 * Returns a string representation of this list. The string
1003 * representation consists of the string representations of the list's
1004 * elements in the order they are returned by its iterator, enclosed in
1005 * square brackets ({@code "[]"}). Adjacent elements are separated by
1006 * the characters {@code ", "} (comma and space). Elements are
1007 * converted to strings as by {@link String#valueOf(Object)}.
1008 *
1009 * @return a string representation of this list
1010 */
1011 public String toString() {
1012 return Arrays.toString(getArray());
1013 }
1014
1015 /**
1016 * Compares the specified object with this list for equality.
1017 * Returns {@code true} if the specified object is the same object
1018 * as this object, or if it is also a {@link List} and the sequence
1019 * of elements returned by an {@linkplain List#iterator() iterator}
1020 * over the specified list is the same as the sequence returned by
1021 * an iterator over this list. The two sequences are considered to
1022 * be the same if they have the same length and corresponding
1023 * elements at the same position in the sequence are <em>equal</em>.
1024 * Two elements {@code e1} and {@code e2} are considered
1025 * <em>equal</em> if {@code (e1==null ? e2==null : e1.equals(e2))}.
1026 *
1027 * @param o the object to be compared for equality with this list
1028 * @return {@code true} if the specified object is equal to this list
1029 */
1030 public boolean equals(Object o) {
1031 if (o == this)
1032 return true;
1033 if (!(o instanceof List))
1034 return false;
1035
1036 List<?> list = (List<?>)(o);
1037 Iterator<?> it = list.iterator();
1038 Object[] elements = getArray();
1039 int len = elements.length;
1040 for (int i = 0; i < len; ++i)
1041 if (!it.hasNext() || !eq(elements[i], it.next()))
1042 return false;
1043 if (it.hasNext())
1044 return false;
1045 return true;
1046 }
1047
1048 /**
1049 * Returns the hash code value for this list.
1050 *
1051 * <p>This implementation uses the definition in {@link List#hashCode}.
1052 *
1053 * @return the hash code value for this list
1054 */
1055 public int hashCode() {
1056 int hashCode = 1;
1057 Object[] elements = getArray();
1058 int len = elements.length;
1059 for (int i = 0; i < len; ++i) {
1060 Object obj = elements[i];
1061 hashCode = 31*hashCode + (obj==null ? 0 : obj.hashCode());
1062 }
1063 return hashCode;
1064 }
1065
1066 /**
1067 * Returns an iterator over the elements in this list in proper sequence.
1068 *
1069 * <p>The returned iterator provides a snapshot of the state of the list
1070 * when the iterator was constructed. No synchronization is needed while
1071 * traversing the iterator. The iterator does <em>NOT</em> support the
1072 * {@code remove} method.
1073 *
1074 * @return an iterator over the elements in this list in proper sequence
1075 */
1076 public Iterator<E> iterator() {
1077 return new COWIterator<E>(getArray(), 0);
1078 }
1079
1080 /**
1081 * {@inheritDoc}
1082 *
1083 * <p>The returned iterator provides a snapshot of the state of the list
1084 * when the iterator was constructed. No synchronization is needed while
1085 * traversing the iterator. The iterator does <em>NOT</em> support the
1086 * {@code remove}, {@code set} or {@code add} methods.
1087 */
1088 public ListIterator<E> listIterator() {
1089 return new COWIterator<E>(getArray(), 0);
1090 }
1091
1092 /**
1093 * {@inheritDoc}
1094 *
1095 * <p>The returned iterator provides a snapshot of the state of the list
1096 * when the iterator was constructed. No synchronization is needed while
1097 * traversing the iterator. The iterator does <em>NOT</em> support the
1098 * {@code remove}, {@code set} or {@code add} methods.
1099 *
1100 * @throws IndexOutOfBoundsException {@inheritDoc}
1101 */
1102 public ListIterator<E> listIterator(int index) {
1103 Object[] elements = getArray();
1104 int len = elements.length;
1105 if (index < 0 || index > len)
1106 throw new IndexOutOfBoundsException("Index: "+index);
1107
1108 return new COWIterator<E>(elements, index);
1109 }
1110
1111 /**
1112 * Returns a {@link Spliterator} over the elements in this list.
1113 *
1114 * <p>The {@code Spliterator} reports {@link Spliterator#IMMUTABLE},
1115 * {@link Spliterator#ORDERED}, {@link Spliterator#SIZED}, and
1116 * {@link Spliterator#SUBSIZED}.
1117 *
1118 * <p>The spliterator provides a snapshot of the state of the list
1119 * when the spliterator was constructed. No synchronization is needed while
1120 * operating on the spliterator.
1121 *
1122 * @return a {@code Spliterator} over the elements in this list
1123 * @since 1.8
1124 */
1125 public Spliterator<E> spliterator() {
1126 return Spliterators.spliterator
1127 (getArray(), Spliterator.IMMUTABLE | Spliterator.ORDERED);
1128 }
1129
1130 static final class COWIterator<E> implements ListIterator<E> {
1131 /** Snapshot of the array */
1132 private final Object[] snapshot;
1133 /** Index of element to be returned by subsequent call to next. */
1134 private int cursor;
1135
1136 private COWIterator(Object[] elements, int initialCursor) {
1137 cursor = initialCursor;
1138 snapshot = elements;
1139 }
1140
1141 public boolean hasNext() {
1142 return cursor < snapshot.length;
1143 }
1144
1145 public boolean hasPrevious() {
1146 return cursor > 0;
1147 }
1148
1149 @SuppressWarnings("unchecked")
1150 public E next() {
1151 if (! hasNext())
1152 throw new NoSuchElementException();
1153 return (E) snapshot[cursor++];
1154 }
1155
1156 @SuppressWarnings("unchecked")
1157 public E previous() {
1158 if (! hasPrevious())
1159 throw new NoSuchElementException();
1160 return (E) snapshot[--cursor];
1161 }
1162
1163 public int nextIndex() {
1164 return cursor;
1165 }
1166
1167 public int previousIndex() {
1168 return cursor-1;
1169 }
1170
1171 /**
1172 * Not supported. Always throws UnsupportedOperationException.
1173 * @throws UnsupportedOperationException always; {@code remove}
1174 * is not supported by this iterator.
1175 */
1176 public void remove() {
1177 throw new UnsupportedOperationException();
1178 }
1179
1180 /**
1181 * Not supported. Always throws UnsupportedOperationException.
1182 * @throws UnsupportedOperationException always; {@code set}
1183 * is not supported by this iterator.
1184 */
1185 public void set(E e) {
1186 throw new UnsupportedOperationException();
1187 }
1188
1189 /**
1190 * Not supported. Always throws UnsupportedOperationException.
1191 * @throws UnsupportedOperationException always; {@code add}
1192 * is not supported by this iterator.
1193 */
1194 public void add(E e) {
1195 throw new UnsupportedOperationException();
1196 }
1197
1198 @Override
1199 public void forEachRemaining(Consumer<? super E> action) {
1200 Objects.requireNonNull(action);
1201 Object[] elements = snapshot;
1202 final int size = elements.length;
1203 for (int i = cursor; i < size; i++) {
1204 @SuppressWarnings("unchecked") E e = (E) elements[i];
1205 action.accept(e);
1206 }
1207 cursor = size;
1208 }
1209 }
1210
1211 /**
1212 * Returns a view of the portion of this list between
1213 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
1214 * The returned list is backed by this list, so changes in the
1215 * returned list are reflected in this list.
1216 *
1217 * <p>The semantics of the list returned by this method become
1218 * undefined if the backing list (i.e., this list) is modified in
1219 * any way other than via the returned list.
1220 *
1221 * @param fromIndex low endpoint (inclusive) of the subList
1222 * @param toIndex high endpoint (exclusive) of the subList
1223 * @return a view of the specified range within this list
1224 * @throws IndexOutOfBoundsException {@inheritDoc}
1225 */
1226 public List<E> subList(int fromIndex, int toIndex) {
1227 final ReentrantLock lock = this.lock;
1228 lock.lock();
1229 try {
1230 Object[] elements = getArray();
1231 int len = elements.length;
1232 if (fromIndex < 0 || toIndex > len || fromIndex > toIndex)
1233 throw new IndexOutOfBoundsException();
1234 return new COWSubList<E>(this, fromIndex, toIndex);
1235 } finally {
1236 lock.unlock();
1237 }
1238 }
1239
1240 /**
1241 * Sublist for CopyOnWriteArrayList.
1242 * This class extends AbstractList merely for convenience, to
1243 * avoid having to define addAll, etc. This doesn't hurt, but
1244 * is wasteful. This class does not need or use modCount
1245 * mechanics in AbstractList, but does need to check for
1246 * concurrent modification using similar mechanics. On each
1247 * operation, the array that we expect the backing list to use
1248 * is checked and updated. Since we do this for all of the
1249 * base operations invoked by those defined in AbstractList,
1250 * all is well. While inefficient, this is not worth
1251 * improving. The kinds of list operations inherited from
1252 * AbstractList are already so slow on COW sublists that
1253 * adding a bit more space/time doesn't seem even noticeable.
1254 */
1255 private static class COWSubList<E>
1256 extends AbstractList<E>
1257 implements RandomAccess
1258 {
1259 private final CopyOnWriteArrayList<E> l;
1260 private final int offset;
1261 private int size;
1262 private Object[] expectedArray;
1263
1264 // only call this holding l's lock
1265 COWSubList(CopyOnWriteArrayList<E> list,
1266 int fromIndex, int toIndex) {
1267 l = list;
1268 expectedArray = l.getArray();
1269 offset = fromIndex;
1270 size = toIndex - fromIndex;
1271 }
1272
1273 // only call this holding l's lock
1274 private void checkForComodification() {
1275 if (l.getArray() != expectedArray)
1276 throw new ConcurrentModificationException();
1277 }
1278
1279 // only call this holding l's lock
1280 private void rangeCheck(int index) {
1281 if (index < 0 || index >= size)
1282 throw new IndexOutOfBoundsException("Index: "+index+
1283 ",Size: "+size);
1284 }
1285
1286 public E set(int index, E element) {
1287 final ReentrantLock lock = l.lock;
1288 lock.lock();
1289 try {
1290 rangeCheck(index);
1291 checkForComodification();
1292 E x = l.set(index+offset, element);
1293 expectedArray = l.getArray();
1294 return x;
1295 } finally {
1296 lock.unlock();
1297 }
1298 }
1299
1300 public E get(int index) {
1301 final ReentrantLock lock = l.lock;
1302 lock.lock();
1303 try {
1304 rangeCheck(index);
1305 checkForComodification();
1306 return l.get(index+offset);
1307 } finally {
1308 lock.unlock();
1309 }
1310 }
1311
1312 public int size() {
1313 final ReentrantLock lock = l.lock;
1314 lock.lock();
1315 try {
1316 checkForComodification();
1317 return size;
1318 } finally {
1319 lock.unlock();
1320 }
1321 }
1322
1323 public void add(int index, E element) {
1324 final ReentrantLock lock = l.lock;
1325 lock.lock();
1326 try {
1327 checkForComodification();
1328 if (index < 0 || index > size)
1329 throw new IndexOutOfBoundsException();
1330 l.add(index+offset, element);
1331 expectedArray = l.getArray();
1332 size++;
1333 } finally {
1334 lock.unlock();
1335 }
1336 }
1337
1338 public void clear() {
1339 final ReentrantLock lock = l.lock;
1340 lock.lock();
1341 try {
1342 checkForComodification();
1343 l.removeRange(offset, offset+size);
1344 expectedArray = l.getArray();
1345 size = 0;
1346 } finally {
1347 lock.unlock();
1348 }
1349 }
1350
1351 public E remove(int index) {
1352 final ReentrantLock lock = l.lock;
1353 lock.lock();
1354 try {
1355 rangeCheck(index);
1356 checkForComodification();
1357 E result = l.remove(index+offset);
1358 expectedArray = l.getArray();
1359 size--;
1360 return result;
1361 } finally {
1362 lock.unlock();
1363 }
1364 }
1365
1366 public boolean remove(Object o) {
1367 int index = indexOf(o);
1368 if (index == -1)
1369 return false;
1370 remove(index);
1371 return true;
1372 }
1373
1374 public Iterator<E> iterator() {
1375 final ReentrantLock lock = l.lock;
1376 lock.lock();
1377 try {
1378 checkForComodification();
1379 return new COWSubListIterator<E>(l, 0, offset, size);
1380 } finally {
1381 lock.unlock();
1382 }
1383 }
1384
1385 public ListIterator<E> listIterator(int index) {
1386 final ReentrantLock lock = l.lock;
1387 lock.lock();
1388 try {
1389 checkForComodification();
1390 if (index < 0 || index > size)
1391 throw new IndexOutOfBoundsException("Index: "+index+
1392 ", Size: "+size);
1393 return new COWSubListIterator<E>(l, index, offset, size);
1394 } finally {
1395 lock.unlock();
1396 }
1397 }
1398
1399 public List<E> subList(int fromIndex, int toIndex) {
1400 final ReentrantLock lock = l.lock;
1401 lock.lock();
1402 try {
1403 checkForComodification();
1404 if (fromIndex < 0 || toIndex > size || fromIndex > toIndex)
1405 throw new IndexOutOfBoundsException();
1406 return new COWSubList<E>(l, fromIndex + offset,
1407 toIndex + offset);
1408 } finally {
1409 lock.unlock();
1410 }
1411 }
1412
1413 public void forEach(Consumer<? super E> action) {
1414 if (action == null) throw new NullPointerException();
1415 int lo = offset;
1416 int hi = offset + size;
1417 Object[] a = expectedArray;
1418 if (l.getArray() != a)
1419 throw new ConcurrentModificationException();
1420 if (lo < 0 || hi > a.length)
1421 throw new IndexOutOfBoundsException();
1422 for (int i = lo; i < hi; ++i) {
1423 @SuppressWarnings("unchecked") E e = (E) a[i];
1424 action.accept(e);
1425 }
1426 }
1427
1428 public void replaceAll(UnaryOperator<E> operator) {
1429 if (operator == null) throw new NullPointerException();
1430 final ReentrantLock lock = l.lock;
1431 lock.lock();
1432 try {
1433 int lo = offset;
1434 int hi = offset + size;
1435 Object[] elements = expectedArray;
1436 if (l.getArray() != elements)
1437 throw new ConcurrentModificationException();
1438 int len = elements.length;
1439 if (lo < 0 || hi > len)
1440 throw new IndexOutOfBoundsException();
1441 Object[] newElements = Arrays.copyOf(elements, len);
1442 for (int i = lo; i < hi; ++i) {
1443 @SuppressWarnings("unchecked") E e = (E) elements[i];
1444 newElements[i] = operator.apply(e);
1445 }
1446 l.setArray(expectedArray = newElements);
1447 } finally {
1448 lock.unlock();
1449 }
1450 }
1451
1452 public void sort(Comparator<? super E> c) {
1453 final ReentrantLock lock = l.lock;
1454 lock.lock();
1455 try {
1456 int lo = offset;
1457 int hi = offset + size;
1458 Object[] elements = expectedArray;
1459 if (l.getArray() != elements)
1460 throw new ConcurrentModificationException();
1461 int len = elements.length;
1462 if (lo < 0 || hi > len)
1463 throw new IndexOutOfBoundsException();
1464 Object[] newElements = Arrays.copyOf(elements, len);
1465 @SuppressWarnings("unchecked") E[] es = (E[])newElements;
1466 Arrays.sort(es, lo, hi, c);
1467 l.setArray(expectedArray = newElements);
1468 } finally {
1469 lock.unlock();
1470 }
1471 }
1472
1473 public boolean removeAll(Collection<?> c) {
1474 if (c == null) throw new NullPointerException();
1475 boolean removed = false;
1476 final ReentrantLock lock = l.lock;
1477 lock.lock();
1478 try {
1479 int n = size;
1480 if (n > 0) {
1481 int lo = offset;
1482 int hi = offset + n;
1483 Object[] elements = expectedArray;
1484 if (l.getArray() != elements)
1485 throw new ConcurrentModificationException();
1486 int len = elements.length;
1487 if (lo < 0 || hi > len)
1488 throw new IndexOutOfBoundsException();
1489 int newSize = 0;
1490 Object[] temp = new Object[n];
1491 for (int i = lo; i < hi; ++i) {
1492 Object element = elements[i];
1493 if (!c.contains(element))
1494 temp[newSize++] = element;
1495 }
1496 if (newSize != n) {
1497 Object[] newElements = new Object[len - n + newSize];
1498 System.arraycopy(elements, 0, newElements, 0, lo);
1499 System.arraycopy(temp, 0, newElements, lo, newSize);
1500 System.arraycopy(elements, hi, newElements,
1501 lo + newSize, len - hi);
1502 size = newSize;
1503 removed = true;
1504 l.setArray(expectedArray = newElements);
1505 }
1506 }
1507 } finally {
1508 lock.unlock();
1509 }
1510 return removed;
1511 }
1512
1513 public boolean retainAll(Collection<?> c) {
1514 if (c == null) throw new NullPointerException();
1515 boolean removed = false;
1516 final ReentrantLock lock = l.lock;
1517 lock.lock();
1518 try {
1519 int n = size;
1520 if (n > 0) {
1521 int lo = offset;
1522 int hi = offset + n;
1523 Object[] elements = expectedArray;
1524 if (l.getArray() != elements)
1525 throw new ConcurrentModificationException();
1526 int len = elements.length;
1527 if (lo < 0 || hi > len)
1528 throw new IndexOutOfBoundsException();
1529 int newSize = 0;
1530 Object[] temp = new Object[n];
1531 for (int i = lo; i < hi; ++i) {
1532 Object element = elements[i];
1533 if (c.contains(element))
1534 temp[newSize++] = element;
1535 }
1536 if (newSize != n) {
1537 Object[] newElements = new Object[len - n + newSize];
1538 System.arraycopy(elements, 0, newElements, 0, lo);
1539 System.arraycopy(temp, 0, newElements, lo, newSize);
1540 System.arraycopy(elements, hi, newElements,
1541 lo + newSize, len - hi);
1542 size = newSize;
1543 removed = true;
1544 l.setArray(expectedArray = newElements);
1545 }
1546 }
1547 } finally {
1548 lock.unlock();
1549 }
1550 return removed;
1551 }
1552
1553 public boolean removeIf(Predicate<? super E> filter) {
1554 if (filter == null) throw new NullPointerException();
1555 boolean removed = false;
1556 final ReentrantLock lock = l.lock;
1557 lock.lock();
1558 try {
1559 int n = size;
1560 if (n > 0) {
1561 int lo = offset;
1562 int hi = offset + n;
1563 Object[] elements = expectedArray;
1564 if (l.getArray() != elements)
1565 throw new ConcurrentModificationException();
1566 int len = elements.length;
1567 if (lo < 0 || hi > len)
1568 throw new IndexOutOfBoundsException();
1569 int newSize = 0;
1570 Object[] temp = new Object[n];
1571 for (int i = lo; i < hi; ++i) {
1572 @SuppressWarnings("unchecked") E e = (E) elements[i];
1573 if (!filter.test(e))
1574 temp[newSize++] = e;
1575 }
1576 if (newSize != n) {
1577 Object[] newElements = new Object[len - n + newSize];
1578 System.arraycopy(elements, 0, newElements, 0, lo);
1579 System.arraycopy(temp, 0, newElements, lo, newSize);
1580 System.arraycopy(elements, hi, newElements,
1581 lo + newSize, len - hi);
1582 size = newSize;
1583 removed = true;
1584 l.setArray(expectedArray = newElements);
1585 }
1586 }
1587 } finally {
1588 lock.unlock();
1589 }
1590 return removed;
1591 }
1592
1593 public Spliterator<E> spliterator() {
1594 int lo = offset;
1595 int hi = offset + size;
1596 Object[] a = expectedArray;
1597 if (l.getArray() != a)
1598 throw new ConcurrentModificationException();
1599 if (lo < 0 || hi > a.length)
1600 throw new IndexOutOfBoundsException();
1601 return Spliterators.spliterator
1602 (a, lo, hi, Spliterator.IMMUTABLE | Spliterator.ORDERED);
1603 }
1604
1605 }
1606
1607 private static class COWSubListIterator<E> implements ListIterator<E> {
1608 private final ListIterator<E> it;
1609 private final int offset;
1610 private final int size;
1611
1612 COWSubListIterator(List<E> l, int index, int offset, int size) {
1613 this.offset = offset;
1614 this.size = size;
1615 it = l.listIterator(index+offset);
1616 }
1617
1618 public boolean hasNext() {
1619 return nextIndex() < size;
1620 }
1621
1622 public E next() {
1623 if (hasNext())
1624 return it.next();
1625 else
1626 throw new NoSuchElementException();
1627 }
1628
1629 public boolean hasPrevious() {
1630 return previousIndex() >= 0;
1631 }
1632
1633 public E previous() {
1634 if (hasPrevious())
1635 return it.previous();
1636 else
1637 throw new NoSuchElementException();
1638 }
1639
1640 public int nextIndex() {
1641 return it.nextIndex() - offset;
1642 }
1643
1644 public int previousIndex() {
1645 return it.previousIndex() - offset;
1646 }
1647
1648 public void remove() {
1649 throw new UnsupportedOperationException();
1650 }
1651
1652 public void set(E e) {
1653 throw new UnsupportedOperationException();
1654 }
1655
1656 public void add(E e) {
1657 throw new UnsupportedOperationException();
1658 }
1659
1660 @Override
1661 public void forEachRemaining(Consumer<? super E> action) {
1662 Objects.requireNonNull(action);
1663 int s = size;
1664 ListIterator<E> i = it;
1665 while (nextIndex() < s) {
1666 action.accept(i.next());
1667 }
1668 }
1669 }
1670
1671 // Support for resetting lock while deserializing
1672 private void resetLock() {
1673 UNSAFE.putObjectVolatile(this, lockOffset, new ReentrantLock());
1674 }
1675 private static final sun.misc.Unsafe UNSAFE;
1676 private static final long lockOffset;
1677 static {
1678 try {
1679 UNSAFE = sun.misc.Unsafe.getUnsafe();
1680 Class<?> k = CopyOnWriteArrayList.class;
1681 lockOffset = UNSAFE.objectFieldOffset
1682 (k.getDeclaredField("lock"));
1683 } catch (Exception e) {
1684 throw new Error(e);
1685 }
1686 }
1687 }