1 /*
2 * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.util;
27
28 import java.util.function.Consumer;
29 import java.util.function.Predicate;
30 import java.util.function.UnaryOperator;
31 import jdk.internal.access.SharedSecrets;
32
33 /**
34 * Resizable-array implementation of the {@code List} interface. Implements
35 * all optional list operations, and permits all elements, including
36 * {@code null}. In addition to implementing the {@code List} interface,
37 * this class provides methods to manipulate the size of the array that is
38 * used internally to store the list. (This class is roughly equivalent to
39 * {@code Vector}, except that it is unsynchronized.)
40 *
41 * <p>The {@code size}, {@code isEmpty}, {@code get}, {@code set},
42 * {@code iterator}, and {@code listIterator} operations run in constant
43 * time. The {@code add} operation runs in <i>amortized constant time</i>,
44 * that is, adding n elements requires O(n) time. All of the other operations
45 * run in linear time (roughly speaking). The constant factor is low compared
46 * to that for the {@code LinkedList} implementation.
47 *
48 * <p>Each {@code ArrayList} instance has a <i>capacity</i>. The capacity is
49 * the size of the array used to store the elements in the list. It is always
50 * at least as large as the list size. As elements are added to an ArrayList,
51 * its capacity grows automatically. The details of the growth policy are not
52 * specified beyond the fact that adding an element has constant amortized
53 * time cost.
54 *
55 * <p>An application can increase the capacity of an {@code ArrayList} instance
56 * before adding a large number of elements using the {@code ensureCapacity}
57 * operation. This may reduce the amount of incremental reallocation.
58 *
59 * <p><strong>Note that this implementation is not synchronized.</strong>
60 * If multiple threads access an {@code ArrayList} instance concurrently,
61 * and at least one of the threads modifies the list structurally, it
62 * <i>must</i> be synchronized externally. (A structural modification is
63 * any operation that adds or deletes one or more elements, or explicitly
64 * resizes the backing array; merely setting the value of an element is not
65 * a structural modification.) This is typically accomplished by
66 * synchronizing on some object that naturally encapsulates the list.
67 *
68 * If no such object exists, the list should be "wrapped" using the
69 * {@link Collections#synchronizedList Collections.synchronizedList}
70 * method. This is best done at creation time, to prevent accidental
71 * unsynchronized access to the list:<pre>
72 * List list = Collections.synchronizedList(new ArrayList(...));</pre>
73 *
74 * <p id="fail-fast">
75 * The iterators returned by this class's {@link #iterator() iterator} and
76 * {@link #listIterator(int) listIterator} methods are <em>fail-fast</em>:
77 * if the list is structurally modified at any time after the iterator is
78 * created, in any way except through the iterator's own
79 * {@link ListIterator#remove() remove} or
80 * {@link ListIterator#add(Object) add} methods, the iterator will throw a
81 * {@link ConcurrentModificationException}. Thus, in the face of
82 * concurrent modification, the iterator fails quickly and cleanly, rather
83 * than risking arbitrary, non-deterministic behavior at an undetermined
84 * time in the future.
85 *
86 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
87 * as it is, generally speaking, impossible to make any hard guarantees in the
88 * presence of unsynchronized concurrent modification. Fail-fast iterators
89 * throw {@code ConcurrentModificationException} on a best-effort basis.
90 * Therefore, it would be wrong to write a program that depended on this
91 * exception for its correctness: <i>the fail-fast behavior of iterators
92 * should be used only to detect bugs.</i>
93 *
94 * <p>This class is a member of the
95 * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
96 * Java Collections Framework</a>.
97 *
98 * @param <E> the type of elements in this list
99 *
100 * @author Josh Bloch
101 * @author Neal Gafter
102 * @see Collection
103 * @see List
104 * @see LinkedList
105 * @see Vector
106 * @since 1.2
107 */
108 public class ArrayList<E> extends AbstractList<E>
109 implements List<E>, RandomAccess, Cloneable, java.io.Serializable
110 {
111 private static final long serialVersionUID = 8683452581122892189L;
112
113 /**
114 * Default initial capacity.
115 */
116 private static final int DEFAULT_CAPACITY = 10;
117
118 /**
119 * Shared empty array instance used for empty instances.
120 */
121 private static final Object[] EMPTY_ELEMENTDATA = {};
122
123 /**
124 * Shared empty array instance used for default sized empty instances. We
125 * distinguish this from EMPTY_ELEMENTDATA to know how much to inflate when
126 * first element is added.
127 */
128 private static final Object[] DEFAULTCAPACITY_EMPTY_ELEMENTDATA = {};
129
130 /**
131 * The array buffer into which the elements of the ArrayList are stored.
132 * The capacity of the ArrayList is the length of this array buffer. Any
133 * empty ArrayList with elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA
134 * will be expanded to DEFAULT_CAPACITY when the first element is added.
135 */
136 transient Object[] elementData; // non-private to simplify nested class access
137
138 /**
139 * The size of the ArrayList (the number of elements it contains).
140 *
141 * @serial
142 */
143 private int size;
144
145 /**
146 * Constructs an empty list with the specified initial capacity.
147 *
148 * @param initialCapacity the initial capacity of the list
149 * @throws IllegalArgumentException if the specified initial capacity
150 * is negative
151 */
152 public ArrayList(int initialCapacity) {
153 if (initialCapacity > 0) {
154 this.elementData = new Object[initialCapacity];
155 } else if (initialCapacity == 0) {
156 this.elementData = EMPTY_ELEMENTDATA;
157 } else {
158 throw new IllegalArgumentException("Illegal Capacity: "+
159 initialCapacity);
160 }
161 }
162
163 /**
164 * Constructs an empty list with an initial capacity of ten.
165 */
166 public ArrayList() {
167 this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA;
168 }
169
170 /**
171 * Constructs a list containing the elements of the specified
172 * collection, in the order they are returned by the collection's
173 * iterator.
174 *
175 * @param c the collection whose elements are to be placed into this list
176 * @throws NullPointerException if the specified collection is null
177 */
178 public ArrayList(Collection<? extends E> c) {
179 if (c instanceof ArrayList) {
180 elementData = new Object[((ArrayList)c).elementData.length];
181 System.arraycopy(((ArrayList)c).elementData, 0, elementData, 0, ((ArrayList)c).elementData.length);
182 size = ((ArrayList)c).size;
183 } else {
184 elementData = c.toArray();
185 if ((size = elementData.length) != 0) {
186 // defend against c.toArray (incorrectly) not returning Object[]
187 // (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652)
188 if (elementData.getClass() != Object[].class)
189 elementData = Arrays.copyOf(elementData, size, Object[].class);
190 } else {
191 // replace with empty array.
192 this.elementData = EMPTY_ELEMENTDATA;
193 }
194 }
195 }
196
197 /**
198 * Trims the capacity of this {@code ArrayList} instance to be the
199 * list's current size. An application can use this operation to minimize
200 * the storage of an {@code ArrayList} instance.
201 */
202 public void trimToSize() {
203 modCount++;
204 if (size < elementData.length) {
205 elementData = (size == 0)
206 ? EMPTY_ELEMENTDATA
207 : Arrays.copyOf(elementData, size);
208 }
209 }
210
211 /**
212 * Increases the capacity of this {@code ArrayList} instance, if
213 * necessary, to ensure that it can hold at least the number of elements
214 * specified by the minimum capacity argument.
215 *
216 * @param minCapacity the desired minimum capacity
217 */
218 public void ensureCapacity(int minCapacity) {
219 if (minCapacity > elementData.length
220 && !(elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA
221 && minCapacity <= DEFAULT_CAPACITY)) {
222 modCount++;
223 grow(minCapacity);
224 }
225 }
226
227 /**
228 * The maximum size of array to allocate (unless necessary).
229 * Some VMs reserve some header words in an array.
230 * Attempts to allocate larger arrays may result in
231 * OutOfMemoryError: Requested array size exceeds VM limit
232 */
233 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
234
235 /**
236 * Increases the capacity to ensure that it can hold at least the
237 * number of elements specified by the minimum capacity argument.
238 *
239 * @param minCapacity the desired minimum capacity
240 * @throws OutOfMemoryError if minCapacity is less than zero
241 */
242 private Object[] grow(int minCapacity) {
243 return elementData = Arrays.copyOf(elementData,
244 newCapacity(minCapacity));
245 }
246
247 private Object[] grow() {
248 return grow(size + 1);
249 }
250
251 /**
252 * Returns a capacity at least as large as the given minimum capacity.
253 * Returns the current capacity increased by 50% if that suffices.
254 * Will not return a capacity greater than MAX_ARRAY_SIZE unless
255 * the given minimum capacity is greater than MAX_ARRAY_SIZE.
256 *
257 * @param minCapacity the desired minimum capacity
258 * @throws OutOfMemoryError if minCapacity is less than zero
259 */
260 private int newCapacity(int minCapacity) {
261 // overflow-conscious code
262 int oldCapacity = elementData.length;
263 int newCapacity = oldCapacity + (oldCapacity >> 1);
264 if (newCapacity - minCapacity <= 0) {
265 if (elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA)
266 return Math.max(DEFAULT_CAPACITY, minCapacity);
267 if (minCapacity < 0) // overflow
268 throw new OutOfMemoryError();
269 return minCapacity;
270 }
271 return (newCapacity - MAX_ARRAY_SIZE <= 0)
272 ? newCapacity
273 : hugeCapacity(minCapacity);
274 }
275
276 private static int hugeCapacity(int minCapacity) {
277 if (minCapacity < 0) // overflow
278 throw new OutOfMemoryError();
279 return (minCapacity > MAX_ARRAY_SIZE)
280 ? Integer.MAX_VALUE
281 : MAX_ARRAY_SIZE;
282 }
283
284 /**
285 * Returns the number of elements in this list.
286 *
287 * @return the number of elements in this list
288 */
289 public int size() {
290 return size;
291 }
292
293 /**
294 * Returns {@code true} if this list contains no elements.
295 *
296 * @return {@code true} if this list contains no elements
297 */
298 public boolean isEmpty() {
299 return size == 0;
300 }
301
302 /**
303 * Returns {@code true} if this list contains the specified element.
304 * More formally, returns {@code true} if and only if this list contains
305 * at least one element {@code e} such that
306 * {@code Objects.equals(o, e)}.
307 *
308 * @param o element whose presence in this list is to be tested
309 * @return {@code true} if this list contains the specified element
310 */
311 public boolean contains(Object o) {
312 return indexOf(o) >= 0;
313 }
314
315 /**
316 * Returns the index of the first occurrence of the specified element
317 * in this list, or -1 if this list does not contain the element.
318 * More formally, returns the lowest index {@code i} such that
319 * {@code Objects.equals(o, get(i))},
320 * or -1 if there is no such index.
321 */
322 public int indexOf(Object o) {
323 return indexOfRange(o, 0, size);
324 }
325
326 int indexOfRange(Object o, int start, int end) {
327 Object[] es = elementData;
328 if (o == null) {
329 for (int i = start; i < end; i++) {
330 if (es[i] == null) {
331 return i;
332 }
333 }
334 } else {
335 for (int i = start; i < end; i++) {
336 if (o.equals(es[i])) {
337 return i;
338 }
339 }
340 }
341 return -1;
342 }
343
344 /**
345 * Returns the index of the last occurrence of the specified element
346 * in this list, or -1 if this list does not contain the element.
347 * More formally, returns the highest index {@code i} such that
348 * {@code Objects.equals(o, get(i))},
349 * or -1 if there is no such index.
350 */
351 public int lastIndexOf(Object o) {
352 return lastIndexOfRange(o, 0, size);
353 }
354
355 int lastIndexOfRange(Object o, int start, int end) {
356 Object[] es = elementData;
357 if (o == null) {
358 for (int i = end - 1; i >= start; i--) {
359 if (es[i] == null) {
360 return i;
361 }
362 }
363 } else {
364 for (int i = end - 1; i >= start; i--) {
365 if (o.equals(es[i])) {
366 return i;
367 }
368 }
369 }
370 return -1;
371 }
372
373 /**
374 * Returns a shallow copy of this {@code ArrayList} instance. (The
375 * elements themselves are not copied.)
376 *
377 * @return a clone of this {@code ArrayList} instance
378 */
379 public Object clone() {
380 try {
381 ArrayList<?> v = (ArrayList<?>) super.clone();
382 v.elementData = Arrays.copyOf(elementData, size);
383 v.modCount = 0;
384 return v;
385 } catch (CloneNotSupportedException e) {
386 // this shouldn't happen, since we are Cloneable
387 throw new InternalError(e);
388 }
389 }
390
391 /**
392 * Returns an array containing all of the elements in this list
393 * in proper sequence (from first to last element).
394 *
395 * <p>The returned array will be "safe" in that no references to it are
396 * maintained by this list. (In other words, this method must allocate
397 * a new array). The caller is thus free to modify the returned array.
398 *
399 * <p>This method acts as bridge between array-based and collection-based
400 * APIs.
401 *
402 * @return an array containing all of the elements in this list in
403 * proper sequence
404 */
405 public Object[] toArray() {
406 return Arrays.copyOf(elementData, size);
407 }
408
409 /**
410 * Returns an array containing all of the elements in this list in proper
411 * sequence (from first to last element); the runtime type of the returned
412 * array is that of the specified array. If the list fits in the
413 * specified array, it is returned therein. Otherwise, a new array is
414 * allocated with the runtime type of the specified array and the size of
415 * this list.
416 *
417 * <p>If the list fits in the specified array with room to spare
418 * (i.e., the array has more elements than the list), the element in
419 * the array immediately following the end of the collection is set to
420 * {@code null}. (This is useful in determining the length of the
421 * list <i>only</i> if the caller knows that the list does not contain
422 * any null elements.)
423 *
424 * @param a the array into which the elements of the list are to
425 * be stored, if it is big enough; otherwise, a new array of the
426 * same runtime type is allocated for this purpose.
427 * @return an array containing the elements of the list
428 * @throws ArrayStoreException if the runtime type of the specified array
429 * is not a supertype of the runtime type of every element in
430 * this list
431 * @throws NullPointerException if the specified array is null
432 */
433 @SuppressWarnings("unchecked")
434 public <T> T[] toArray(T[] a) {
435 if (a.length < size)
436 // Make a new array of a's runtime type, but my contents:
437 return (T[]) Arrays.copyOf(elementData, size, a.getClass());
438 System.arraycopy(elementData, 0, a, 0, size);
439 if (a.length > size)
440 a[size] = null;
441 return a;
442 }
443
444 // Positional Access Operations
445
446 @SuppressWarnings("unchecked")
447 E elementData(int index) {
448 return (E) elementData[index];
449 }
450
451 @SuppressWarnings("unchecked")
452 static <E> E elementAt(Object[] es, int index) {
453 return (E) es[index];
454 }
455
456 /**
457 * Returns the element at the specified position in this list.
458 *
459 * @param index index of the element to return
460 * @return the element at the specified position in this list
461 * @throws IndexOutOfBoundsException {@inheritDoc}
462 */
463 public E get(int index) {
464 Objects.checkIndex(index, size);
465 return elementData(index);
466 }
467
468 /**
469 * Replaces the element at the specified position in this list with
470 * the specified element.
471 *
472 * @param index index of the element to replace
473 * @param element element to be stored at the specified position
474 * @return the element previously at the specified position
475 * @throws IndexOutOfBoundsException {@inheritDoc}
476 */
477 public E set(int index, E element) {
478 Objects.checkIndex(index, size);
479 E oldValue = elementData(index);
480 elementData[index] = element;
481 return oldValue;
482 }
483
484 /**
485 * This helper method split out from add(E) to keep method
486 * bytecode size under 35 (the -XX:MaxInlineSize default value),
487 * which helps when add(E) is called in a C1-compiled loop.
488 */
489 private void add(E e, Object[] elementData, int s) {
490 if (s == elementData.length)
491 elementData = grow();
492 elementData[s] = e;
493 size = s + 1;
494 }
495
496 /**
497 * Appends the specified element to the end of this list.
498 *
499 * @param e element to be appended to this list
500 * @return {@code true} (as specified by {@link Collection#add})
501 */
502 public boolean add(E e) {
503 modCount++;
504 add(e, elementData, size);
505 return true;
506 }
507
508 /**
509 * Inserts the specified element at the specified position in this
510 * list. Shifts the element currently at that position (if any) and
511 * any subsequent elements to the right (adds one to their indices).
512 *
513 * @param index index at which the specified element is to be inserted
514 * @param element element to be inserted
515 * @throws IndexOutOfBoundsException {@inheritDoc}
516 */
517 public void add(int index, E element) {
518 rangeCheckForAdd(index);
519 modCount++;
520 final int s;
521 Object[] elementData;
522 if ((s = size) == (elementData = this.elementData).length)
523 elementData = grow();
524 System.arraycopy(elementData, index,
525 elementData, index + 1,
526 s - index);
527 elementData[index] = element;
528 size = s + 1;
529 }
530
531 /**
532 * Removes the element at the specified position in this list.
533 * Shifts any subsequent elements to the left (subtracts one from their
534 * indices).
535 *
536 * @param index the index of the element to be removed
537 * @return the element that was removed from the list
538 * @throws IndexOutOfBoundsException {@inheritDoc}
539 */
540 public E remove(int index) {
541 Objects.checkIndex(index, size);
542 final Object[] es = elementData;
543
544 @SuppressWarnings("unchecked") E oldValue = (E) es[index];
545 fastRemove(es, index);
546
547 return oldValue;
548 }
549
550 /**
551 * {@inheritDoc}
552 */
553 public boolean equals(Object o) {
554 if (o == this) {
555 return true;
556 }
557
558 if (!(o instanceof List)) {
559 return false;
560 }
561
562 final int expectedModCount = modCount;
563 // ArrayList can be subclassed and given arbitrary behavior, but we can
564 // still deal with the common case where o is ArrayList precisely
565 boolean equal = (o.getClass() == ArrayList.class)
566 ? equalsArrayList((ArrayList<?>) o)
567 : equalsRange((List<?>) o, 0, size);
568
569 checkForComodification(expectedModCount);
570 return equal;
571 }
572
573 boolean equalsRange(List<?> other, int from, int to) {
574 final Object[] es = elementData;
575 if (to > es.length) {
576 throw new ConcurrentModificationException();
577 }
578 var oit = other.iterator();
579 for (; from < to; from++) {
580 if (!oit.hasNext() || !Objects.equals(es[from], oit.next())) {
581 return false;
582 }
583 }
584 return !oit.hasNext();
585 }
586
587 private boolean equalsArrayList(ArrayList<?> other) {
588 final int otherModCount = other.modCount;
589 final int s = size;
590 boolean equal;
591 if (equal = (s == other.size)) {
592 final Object[] otherEs = other.elementData;
593 final Object[] es = elementData;
594 if (s > es.length || s > otherEs.length) {
595 throw new ConcurrentModificationException();
596 }
597 for (int i = 0; i < s; i++) {
598 if (!Objects.equals(es[i], otherEs[i])) {
599 equal = false;
600 break;
601 }
602 }
603 }
604 other.checkForComodification(otherModCount);
605 return equal;
606 }
607
608 private void checkForComodification(final int expectedModCount) {
609 if (modCount != expectedModCount) {
610 throw new ConcurrentModificationException();
611 }
612 }
613
614 /**
615 * {@inheritDoc}
616 */
617 public int hashCode() {
618 int expectedModCount = modCount;
619 int hash = hashCodeRange(0, size);
620 checkForComodification(expectedModCount);
621 return hash;
622 }
623
624 int hashCodeRange(int from, int to) {
625 final Object[] es = elementData;
626 if (to > es.length) {
627 throw new ConcurrentModificationException();
628 }
629 int hashCode = 1;
630 for (int i = from; i < to; i++) {
631 Object e = es[i];
632 hashCode = 31 * hashCode + (e == null ? 0 : e.hashCode());
633 }
634 return hashCode;
635 }
636
637 /**
638 * Removes the first occurrence of the specified element from this list,
639 * if it is present. If the list does not contain the element, it is
640 * unchanged. More formally, removes the element with the lowest index
641 * {@code i} such that
642 * {@code Objects.equals(o, get(i))}
643 * (if such an element exists). Returns {@code true} if this list
644 * contained the specified element (or equivalently, if this list
645 * changed as a result of the call).
646 *
647 * @param o element to be removed from this list, if present
648 * @return {@code true} if this list contained the specified element
649 */
650 public boolean remove(Object o) {
651 final Object[] es = elementData;
652 final int size = this.size;
653 int i = 0;
654 found: {
655 if (o == null) {
656 for (; i < size; i++)
657 if (es[i] == null)
658 break found;
659 } else {
660 for (; i < size; i++)
661 if (o.equals(es[i]))
662 break found;
663 }
664 return false;
665 }
666 fastRemove(es, i);
667 return true;
668 }
669
670 /**
671 * Private remove method that skips bounds checking and does not
672 * return the value removed.
673 */
674 private void fastRemove(Object[] es, int i) {
675 modCount++;
676 final int newSize;
677 if ((newSize = size - 1) > i)
678 System.arraycopy(es, i + 1, es, i, newSize - i);
679 es[size = newSize] = null;
680 }
681
682 /**
683 * Removes all of the elements from this list. The list will
684 * be empty after this call returns.
685 */
686 public void clear() {
687 modCount++;
688 final Object[] es = elementData;
689 for (int to = size, i = size = 0; i < to; i++)
690 es[i] = null;
691 }
692
693 /**
694 * Appends all of the elements in the specified collection to the end of
695 * this list, in the order that they are returned by the
696 * specified collection's Iterator. The behavior of this operation is
697 * undefined if the specified collection is modified while the operation
698 * is in progress. (This implies that the behavior of this call is
699 * undefined if the specified collection is this list, and this
700 * list is nonempty.)
701 *
702 * @param c collection containing elements to be added to this list
703 * @return {@code true} if this list changed as a result of the call
704 * @throws NullPointerException if the specified collection is null
705 */
706 public boolean addAll(Collection<? extends E> c) {
707 Object[] a = c.toArray();
708 modCount++;
709 int numNew = a.length;
710 if (numNew == 0)
711 return false;
712 Object[] elementData;
713 final int s;
714 if (numNew > (elementData = this.elementData).length - (s = size))
715 elementData = grow(s + numNew);
716 System.arraycopy(a, 0, elementData, s, numNew);
717 size = s + numNew;
718 return true;
719 }
720
721 /**
722 * Inserts all of the elements in the specified collection into this
723 * list, starting at the specified position. Shifts the element
724 * currently at that position (if any) and any subsequent elements to
725 * the right (increases their indices). The new elements will appear
726 * in the list in the order that they are returned by the
727 * specified collection's iterator.
728 *
729 * @param index index at which to insert the first element from the
730 * specified collection
731 * @param c collection containing elements to be added to this list
732 * @return {@code true} if this list changed as a result of the call
733 * @throws IndexOutOfBoundsException {@inheritDoc}
734 * @throws NullPointerException if the specified collection is null
735 */
736 public boolean addAll(int index, Collection<? extends E> c) {
737 rangeCheckForAdd(index);
738
739 Object[] a = c.toArray();
740 modCount++;
741 int numNew = a.length;
742 if (numNew == 0)
743 return false;
744 Object[] elementData;
745 final int s;
746 if (numNew > (elementData = this.elementData).length - (s = size))
747 elementData = grow(s + numNew);
748
749 int numMoved = s - index;
750 if (numMoved > 0)
751 System.arraycopy(elementData, index,
752 elementData, index + numNew,
753 numMoved);
754 System.arraycopy(a, 0, elementData, index, numNew);
755 size = s + numNew;
756 return true;
757 }
758
759 /**
760 * Removes from this list all of the elements whose index is between
761 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
762 * Shifts any succeeding elements to the left (reduces their index).
763 * This call shortens the list by {@code (toIndex - fromIndex)} elements.
764 * (If {@code toIndex==fromIndex}, this operation has no effect.)
765 *
766 * @throws IndexOutOfBoundsException if {@code fromIndex} or
767 * {@code toIndex} is out of range
768 * ({@code fromIndex < 0 ||
769 * toIndex > size() ||
770 * toIndex < fromIndex})
771 */
772 protected void removeRange(int fromIndex, int toIndex) {
773 if (fromIndex > toIndex) {
774 throw new IndexOutOfBoundsException(
775 outOfBoundsMsg(fromIndex, toIndex));
776 }
777 modCount++;
778 shiftTailOverGap(elementData, fromIndex, toIndex);
779 }
780
781 /** Erases the gap from lo to hi, by sliding down following elements. */
782 private void shiftTailOverGap(Object[] es, int lo, int hi) {
783 System.arraycopy(es, hi, es, lo, size - hi);
784 for (int to = size, i = (size -= hi - lo); i < to; i++)
785 es[i] = null;
786 }
787
788 /**
789 * A version of rangeCheck used by add and addAll.
790 */
791 private void rangeCheckForAdd(int index) {
792 if (index > size || index < 0)
793 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
794 }
795
796 /**
797 * Constructs an IndexOutOfBoundsException detail message.
798 * Of the many possible refactorings of the error handling code,
799 * this "outlining" performs best with both server and client VMs.
800 */
801 private String outOfBoundsMsg(int index) {
802 return "Index: "+index+", Size: "+size;
803 }
804
805 /**
806 * A version used in checking (fromIndex > toIndex) condition
807 */
808 private static String outOfBoundsMsg(int fromIndex, int toIndex) {
809 return "From Index: " + fromIndex + " > To Index: " + toIndex;
810 }
811
812 /**
813 * Removes from this list all of its elements that are contained in the
814 * specified collection.
815 *
816 * @param c collection containing elements to be removed from this list
817 * @return {@code true} if this list changed as a result of the call
818 * @throws ClassCastException if the class of an element of this list
819 * is incompatible with the specified collection
820 * (<a href="Collection.html#optional-restrictions">optional</a>)
821 * @throws NullPointerException if this list contains a null element and the
822 * specified collection does not permit null elements
823 * (<a href="Collection.html#optional-restrictions">optional</a>),
824 * or if the specified collection is null
825 * @see Collection#contains(Object)
826 */
827 public boolean removeAll(Collection<?> c) {
828 return batchRemove(c, false, 0, size);
829 }
830
831 /**
832 * Retains only the elements in this list that are contained in the
833 * specified collection. In other words, removes from this list all
834 * of its elements that are not contained in the specified collection.
835 *
836 * @param c collection containing elements to be retained in this list
837 * @return {@code true} if this list changed as a result of the call
838 * @throws ClassCastException if the class of an element of this list
839 * is incompatible with the specified collection
840 * (<a href="Collection.html#optional-restrictions">optional</a>)
841 * @throws NullPointerException if this list contains a null element and the
842 * specified collection does not permit null elements
843 * (<a href="Collection.html#optional-restrictions">optional</a>),
844 * or if the specified collection is null
845 * @see Collection#contains(Object)
846 */
847 public boolean retainAll(Collection<?> c) {
848 return batchRemove(c, true, 0, size);
849 }
850
851 boolean batchRemove(Collection<?> c, boolean complement,
852 final int from, final int end) {
853 Objects.requireNonNull(c);
854 final Object[] es = elementData;
855 int r;
856 // Optimize for initial run of survivors
857 for (r = from;; r++) {
858 if (r == end)
859 return false;
860 if (c.contains(es[r]) != complement)
861 break;
862 }
863 int w = r++;
864 try {
865 for (Object e; r < end; r++)
866 if (c.contains(e = es[r]) == complement)
867 es[w++] = e;
868 } catch (Throwable ex) {
869 // Preserve behavioral compatibility with AbstractCollection,
870 // even if c.contains() throws.
871 System.arraycopy(es, r, es, w, end - r);
872 w += end - r;
873 throw ex;
874 } finally {
875 modCount += end - w;
876 shiftTailOverGap(es, w, end);
877 }
878 return true;
879 }
880
881 /**
882 * Saves the state of the {@code ArrayList} instance to a stream
883 * (that is, serializes it).
884 *
885 * @param s the stream
886 * @throws java.io.IOException if an I/O error occurs
887 * @serialData The length of the array backing the {@code ArrayList}
888 * instance is emitted (int), followed by all of its elements
889 * (each an {@code Object}) in the proper order.
890 */
891 private void writeObject(java.io.ObjectOutputStream s)
892 throws java.io.IOException {
893 // Write out element count, and any hidden stuff
894 int expectedModCount = modCount;
895 s.defaultWriteObject();
896
897 // Write out size as capacity for behavioral compatibility with clone()
898 s.writeInt(size);
899
900 // Write out all elements in the proper order.
901 for (int i=0; i<size; i++) {
902 s.writeObject(elementData[i]);
903 }
904
905 if (modCount != expectedModCount) {
906 throw new ConcurrentModificationException();
907 }
908 }
909
910 /**
911 * Reconstitutes the {@code ArrayList} instance from a stream (that is,
912 * deserializes it).
913 * @param s the stream
914 * @throws ClassNotFoundException if the class of a serialized object
915 * could not be found
916 * @throws java.io.IOException if an I/O error occurs
917 */
918 private void readObject(java.io.ObjectInputStream s)
919 throws java.io.IOException, ClassNotFoundException {
920
921 // Read in size, and any hidden stuff
922 s.defaultReadObject();
923
924 // Read in capacity
925 s.readInt(); // ignored
926
927 if (size > 0) {
928 // like clone(), allocate array based upon size not capacity
929 SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, size);
930 Object[] elements = new Object[size];
931
932 // Read in all elements in the proper order.
933 for (int i = 0; i < size; i++) {
934 elements[i] = s.readObject();
935 }
936
937 elementData = elements;
938 } else if (size == 0) {
939 elementData = EMPTY_ELEMENTDATA;
940 } else {
941 throw new java.io.InvalidObjectException("Invalid size: " + size);
942 }
943 }
944
945 /**
946 * Returns a list iterator over the elements in this list (in proper
947 * sequence), starting at the specified position in the list.
948 * The specified index indicates the first element that would be
949 * returned by an initial call to {@link ListIterator#next next}.
950 * An initial call to {@link ListIterator#previous previous} would
951 * return the element with the specified index minus one.
952 *
953 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
954 *
955 * @throws IndexOutOfBoundsException {@inheritDoc}
956 */
957 public ListIterator<E> listIterator(int index) {
958 rangeCheckForAdd(index);
959 return new ListItr(index);
960 }
961
962 /**
963 * Returns a list iterator over the elements in this list (in proper
964 * sequence).
965 *
966 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
967 *
968 * @see #listIterator(int)
969 */
970 public ListIterator<E> listIterator() {
971 return new ListItr(0);
972 }
973
974 /**
975 * Returns an iterator over the elements in this list in proper sequence.
976 *
977 * <p>The returned iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
978 *
979 * @return an iterator over the elements in this list in proper sequence
980 */
981 public Iterator<E> iterator() {
982 return new Itr();
983 }
984
985 /**
986 * An optimized version of AbstractList.Itr
987 */
988 private class Itr implements Iterator<E> {
989 int cursor; // index of next element to return
990 int lastRet = -1; // index of last element returned; -1 if no such
991 int expectedModCount = modCount;
992
993 // prevent creating a synthetic constructor
994 Itr() {}
995
996 public boolean hasNext() {
997 return cursor != size;
998 }
999
1000 @SuppressWarnings("unchecked")
1001 public E next() {
1002 checkForComodification();
1003 int i = cursor;
1004 if (i >= size)
1005 throw new NoSuchElementException();
1006 Object[] elementData = ArrayList.this.elementData;
1007 if (i >= elementData.length)
1008 throw new ConcurrentModificationException();
1009 cursor = i + 1;
1010 return (E) elementData[lastRet = i];
1011 }
1012
1013 public void remove() {
1014 if (lastRet < 0)
1015 throw new IllegalStateException();
1016 checkForComodification();
1017
1018 try {
1019 ArrayList.this.remove(lastRet);
1020 cursor = lastRet;
1021 lastRet = -1;
1022 expectedModCount = modCount;
1023 } catch (IndexOutOfBoundsException ex) {
1024 throw new ConcurrentModificationException();
1025 }
1026 }
1027
1028 @Override
1029 public void forEachRemaining(Consumer<? super E> action) {
1030 Objects.requireNonNull(action);
1031 final int size = ArrayList.this.size;
1032 int i = cursor;
1033 if (i < size) {
1034 final Object[] es = elementData;
1035 if (i >= es.length)
1036 throw new ConcurrentModificationException();
1037 for (; i < size && modCount == expectedModCount; i++)
1038 action.accept(elementAt(es, i));
1039 // update once at end to reduce heap write traffic
1040 cursor = i;
1041 lastRet = i - 1;
1042 checkForComodification();
1043 }
1044 }
1045
1046 final void checkForComodification() {
1047 if (modCount != expectedModCount)
1048 throw new ConcurrentModificationException();
1049 }
1050 }
1051
1052 /**
1053 * An optimized version of AbstractList.ListItr
1054 */
1055 private class ListItr extends Itr implements ListIterator<E> {
1056 ListItr(int index) {
1057 super();
1058 cursor = index;
1059 }
1060
1061 public boolean hasPrevious() {
1062 return cursor != 0;
1063 }
1064
1065 public int nextIndex() {
1066 return cursor;
1067 }
1068
1069 public int previousIndex() {
1070 return cursor - 1;
1071 }
1072
1073 @SuppressWarnings("unchecked")
1074 public E previous() {
1075 checkForComodification();
1076 int i = cursor - 1;
1077 if (i < 0)
1078 throw new NoSuchElementException();
1079 Object[] elementData = ArrayList.this.elementData;
1080 if (i >= elementData.length)
1081 throw new ConcurrentModificationException();
1082 cursor = i;
1083 return (E) elementData[lastRet = i];
1084 }
1085
1086 public void set(E e) {
1087 if (lastRet < 0)
1088 throw new IllegalStateException();
1089 checkForComodification();
1090
1091 try {
1092 ArrayList.this.set(lastRet, e);
1093 } catch (IndexOutOfBoundsException ex) {
1094 throw new ConcurrentModificationException();
1095 }
1096 }
1097
1098 public void add(E e) {
1099 checkForComodification();
1100
1101 try {
1102 int i = cursor;
1103 ArrayList.this.add(i, e);
1104 cursor = i + 1;
1105 lastRet = -1;
1106 expectedModCount = modCount;
1107 } catch (IndexOutOfBoundsException ex) {
1108 throw new ConcurrentModificationException();
1109 }
1110 }
1111 }
1112
1113 /**
1114 * Returns a view of the portion of this list between the specified
1115 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. (If
1116 * {@code fromIndex} and {@code toIndex} are equal, the returned list is
1117 * empty.) The returned list is backed by this list, so non-structural
1118 * changes in the returned list are reflected in this list, and vice-versa.
1119 * The returned list supports all of the optional list operations.
1120 *
1121 * <p>This method eliminates the need for explicit range operations (of
1122 * the sort that commonly exist for arrays). Any operation that expects
1123 * a list can be used as a range operation by passing a subList view
1124 * instead of a whole list. For example, the following idiom
1125 * removes a range of elements from a list:
1126 * <pre>
1127 * list.subList(from, to).clear();
1128 * </pre>
1129 * Similar idioms may be constructed for {@link #indexOf(Object)} and
1130 * {@link #lastIndexOf(Object)}, and all of the algorithms in the
1131 * {@link Collections} class can be applied to a subList.
1132 *
1133 * <p>The semantics of the list returned by this method become undefined if
1134 * the backing list (i.e., this list) is <i>structurally modified</i> in
1135 * any way other than via the returned list. (Structural modifications are
1136 * those that change the size of this list, or otherwise perturb it in such
1137 * a fashion that iterations in progress may yield incorrect results.)
1138 *
1139 * @throws IndexOutOfBoundsException {@inheritDoc}
1140 * @throws IllegalArgumentException {@inheritDoc}
1141 */
1142 public List<E> subList(int fromIndex, int toIndex) {
1143 subListRangeCheck(fromIndex, toIndex, size);
1144 return new SubList<>(this, fromIndex, toIndex);
1145 }
1146
1147 private static class SubList<E> extends AbstractList<E> implements RandomAccess {
1148 private final ArrayList<E> root;
1149 private final SubList<E> parent;
1150 private final int offset;
1151 private int size;
1152
1153 /**
1154 * Constructs a sublist of an arbitrary ArrayList.
1155 */
1156 public SubList(ArrayList<E> root, int fromIndex, int toIndex) {
1157 this.root = root;
1158 this.parent = null;
1159 this.offset = fromIndex;
1160 this.size = toIndex - fromIndex;
1161 this.modCount = root.modCount;
1162 }
1163
1164 /**
1165 * Constructs a sublist of another SubList.
1166 */
1167 private SubList(SubList<E> parent, int fromIndex, int toIndex) {
1168 this.root = parent.root;
1169 this.parent = parent;
1170 this.offset = parent.offset + fromIndex;
1171 this.size = toIndex - fromIndex;
1172 this.modCount = root.modCount;
1173 }
1174
1175 public E set(int index, E element) {
1176 Objects.checkIndex(index, size);
1177 checkForComodification();
1178 E oldValue = root.elementData(offset + index);
1179 root.elementData[offset + index] = element;
1180 return oldValue;
1181 }
1182
1183 public E get(int index) {
1184 Objects.checkIndex(index, size);
1185 checkForComodification();
1186 return root.elementData(offset + index);
1187 }
1188
1189 public int size() {
1190 checkForComodification();
1191 return size;
1192 }
1193
1194 public void add(int index, E element) {
1195 rangeCheckForAdd(index);
1196 checkForComodification();
1197 root.add(offset + index, element);
1198 updateSizeAndModCount(1);
1199 }
1200
1201 public E remove(int index) {
1202 Objects.checkIndex(index, size);
1203 checkForComodification();
1204 E result = root.remove(offset + index);
1205 updateSizeAndModCount(-1);
1206 return result;
1207 }
1208
1209 protected void removeRange(int fromIndex, int toIndex) {
1210 checkForComodification();
1211 root.removeRange(offset + fromIndex, offset + toIndex);
1212 updateSizeAndModCount(fromIndex - toIndex);
1213 }
1214
1215 public boolean addAll(Collection<? extends E> c) {
1216 return addAll(this.size, c);
1217 }
1218
1219 public boolean addAll(int index, Collection<? extends E> c) {
1220 rangeCheckForAdd(index);
1221 int cSize = c.size();
1222 if (cSize==0)
1223 return false;
1224 checkForComodification();
1225 root.addAll(offset + index, c);
1226 updateSizeAndModCount(cSize);
1227 return true;
1228 }
1229
1230 public void replaceAll(UnaryOperator<E> operator) {
1231 root.replaceAllRange(operator, offset, offset + size);
1232 }
1233
1234 public boolean removeAll(Collection<?> c) {
1235 return batchRemove(c, false);
1236 }
1237
1238 public boolean retainAll(Collection<?> c) {
1239 return batchRemove(c, true);
1240 }
1241
1242 private boolean batchRemove(Collection<?> c, boolean complement) {
1243 checkForComodification();
1244 int oldSize = root.size;
1245 boolean modified =
1246 root.batchRemove(c, complement, offset, offset + size);
1247 if (modified)
1248 updateSizeAndModCount(root.size - oldSize);
1249 return modified;
1250 }
1251
1252 public boolean removeIf(Predicate<? super E> filter) {
1253 checkForComodification();
1254 int oldSize = root.size;
1255 boolean modified = root.removeIf(filter, offset, offset + size);
1256 if (modified)
1257 updateSizeAndModCount(root.size - oldSize);
1258 return modified;
1259 }
1260
1261 public Object[] toArray() {
1262 checkForComodification();
1263 return Arrays.copyOfRange(root.elementData, offset, offset + size);
1264 }
1265
1266 @SuppressWarnings("unchecked")
1267 public <T> T[] toArray(T[] a) {
1268 checkForComodification();
1269 if (a.length < size)
1270 return (T[]) Arrays.copyOfRange(
1271 root.elementData, offset, offset + size, a.getClass());
1272 System.arraycopy(root.elementData, offset, a, 0, size);
1273 if (a.length > size)
1274 a[size] = null;
1275 return a;
1276 }
1277
1278 public boolean equals(Object o) {
1279 if (o == this) {
1280 return true;
1281 }
1282
1283 if (!(o instanceof List)) {
1284 return false;
1285 }
1286
1287 boolean equal = root.equalsRange((List<?>)o, offset, offset + size);
1288 checkForComodification();
1289 return equal;
1290 }
1291
1292 public int hashCode() {
1293 int hash = root.hashCodeRange(offset, offset + size);
1294 checkForComodification();
1295 return hash;
1296 }
1297
1298 public int indexOf(Object o) {
1299 int index = root.indexOfRange(o, offset, offset + size);
1300 checkForComodification();
1301 return index >= 0 ? index - offset : -1;
1302 }
1303
1304 public int lastIndexOf(Object o) {
1305 int index = root.lastIndexOfRange(o, offset, offset + size);
1306 checkForComodification();
1307 return index >= 0 ? index - offset : -1;
1308 }
1309
1310 public boolean contains(Object o) {
1311 return indexOf(o) >= 0;
1312 }
1313
1314 public Iterator<E> iterator() {
1315 return listIterator();
1316 }
1317
1318 public ListIterator<E> listIterator(int index) {
1319 checkForComodification();
1320 rangeCheckForAdd(index);
1321
1322 return new ListIterator<E>() {
1323 int cursor = index;
1324 int lastRet = -1;
1325 int expectedModCount = root.modCount;
1326
1327 public boolean hasNext() {
1328 return cursor != SubList.this.size;
1329 }
1330
1331 @SuppressWarnings("unchecked")
1332 public E next() {
1333 checkForComodification();
1334 int i = cursor;
1335 if (i >= SubList.this.size)
1336 throw new NoSuchElementException();
1337 Object[] elementData = root.elementData;
1338 if (offset + i >= elementData.length)
1339 throw new ConcurrentModificationException();
1340 cursor = i + 1;
1341 return (E) elementData[offset + (lastRet = i)];
1342 }
1343
1344 public boolean hasPrevious() {
1345 return cursor != 0;
1346 }
1347
1348 @SuppressWarnings("unchecked")
1349 public E previous() {
1350 checkForComodification();
1351 int i = cursor - 1;
1352 if (i < 0)
1353 throw new NoSuchElementException();
1354 Object[] elementData = root.elementData;
1355 if (offset + i >= elementData.length)
1356 throw new ConcurrentModificationException();
1357 cursor = i;
1358 return (E) elementData[offset + (lastRet = i)];
1359 }
1360
1361 public void forEachRemaining(Consumer<? super E> action) {
1362 Objects.requireNonNull(action);
1363 final int size = SubList.this.size;
1364 int i = cursor;
1365 if (i < size) {
1366 final Object[] es = root.elementData;
1367 if (offset + i >= es.length)
1368 throw new ConcurrentModificationException();
1369 for (; i < size && modCount == expectedModCount; i++)
1370 action.accept(elementAt(es, offset + i));
1371 // update once at end to reduce heap write traffic
1372 cursor = i;
1373 lastRet = i - 1;
1374 checkForComodification();
1375 }
1376 }
1377
1378 public int nextIndex() {
1379 return cursor;
1380 }
1381
1382 public int previousIndex() {
1383 return cursor - 1;
1384 }
1385
1386 public void remove() {
1387 if (lastRet < 0)
1388 throw new IllegalStateException();
1389 checkForComodification();
1390
1391 try {
1392 SubList.this.remove(lastRet);
1393 cursor = lastRet;
1394 lastRet = -1;
1395 expectedModCount = root.modCount;
1396 } catch (IndexOutOfBoundsException ex) {
1397 throw new ConcurrentModificationException();
1398 }
1399 }
1400
1401 public void set(E e) {
1402 if (lastRet < 0)
1403 throw new IllegalStateException();
1404 checkForComodification();
1405
1406 try {
1407 root.set(offset + lastRet, e);
1408 } catch (IndexOutOfBoundsException ex) {
1409 throw new ConcurrentModificationException();
1410 }
1411 }
1412
1413 public void add(E e) {
1414 checkForComodification();
1415
1416 try {
1417 int i = cursor;
1418 SubList.this.add(i, e);
1419 cursor = i + 1;
1420 lastRet = -1;
1421 expectedModCount = root.modCount;
1422 } catch (IndexOutOfBoundsException ex) {
1423 throw new ConcurrentModificationException();
1424 }
1425 }
1426
1427 final void checkForComodification() {
1428 if (root.modCount != expectedModCount)
1429 throw new ConcurrentModificationException();
1430 }
1431 };
1432 }
1433
1434 public List<E> subList(int fromIndex, int toIndex) {
1435 subListRangeCheck(fromIndex, toIndex, size);
1436 return new SubList<>(this, fromIndex, toIndex);
1437 }
1438
1439 private void rangeCheckForAdd(int index) {
1440 if (index < 0 || index > this.size)
1441 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
1442 }
1443
1444 private String outOfBoundsMsg(int index) {
1445 return "Index: "+index+", Size: "+this.size;
1446 }
1447
1448 private void checkForComodification() {
1449 if (root.modCount != modCount)
1450 throw new ConcurrentModificationException();
1451 }
1452
1453 private void updateSizeAndModCount(int sizeChange) {
1454 SubList<E> slist = this;
1455 do {
1456 slist.size += sizeChange;
1457 slist.modCount = root.modCount;
1458 slist = slist.parent;
1459 } while (slist != null);
1460 }
1461
1462 public Spliterator<E> spliterator() {
1463 checkForComodification();
1464
1465 // ArrayListSpliterator not used here due to late-binding
1466 return new Spliterator<E>() {
1467 private int index = offset; // current index, modified on advance/split
1468 private int fence = -1; // -1 until used; then one past last index
1469 private int expectedModCount; // initialized when fence set
1470
1471 private int getFence() { // initialize fence to size on first use
1472 int hi; // (a specialized variant appears in method forEach)
1473 if ((hi = fence) < 0) {
1474 expectedModCount = modCount;
1475 hi = fence = offset + size;
1476 }
1477 return hi;
1478 }
1479
1480 public ArrayList<E>.ArrayListSpliterator trySplit() {
1481 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1482 // ArrayListSpliterator can be used here as the source is already bound
1483 return (lo >= mid) ? null : // divide range in half unless too small
1484 root.new ArrayListSpliterator(lo, index = mid, expectedModCount);
1485 }
1486
1487 public boolean tryAdvance(Consumer<? super E> action) {
1488 Objects.requireNonNull(action);
1489 int hi = getFence(), i = index;
1490 if (i < hi) {
1491 index = i + 1;
1492 @SuppressWarnings("unchecked") E e = (E)root.elementData[i];
1493 action.accept(e);
1494 if (root.modCount != expectedModCount)
1495 throw new ConcurrentModificationException();
1496 return true;
1497 }
1498 return false;
1499 }
1500
1501 public void forEachRemaining(Consumer<? super E> action) {
1502 Objects.requireNonNull(action);
1503 int i, hi, mc; // hoist accesses and checks from loop
1504 ArrayList<E> lst = root;
1505 Object[] a;
1506 if ((a = lst.elementData) != null) {
1507 if ((hi = fence) < 0) {
1508 mc = modCount;
1509 hi = offset + size;
1510 }
1511 else
1512 mc = expectedModCount;
1513 if ((i = index) >= 0 && (index = hi) <= a.length) {
1514 for (; i < hi; ++i) {
1515 @SuppressWarnings("unchecked") E e = (E) a[i];
1516 action.accept(e);
1517 }
1518 if (lst.modCount == mc)
1519 return;
1520 }
1521 }
1522 throw new ConcurrentModificationException();
1523 }
1524
1525 public long estimateSize() {
1526 return getFence() - index;
1527 }
1528
1529 public int characteristics() {
1530 return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
1531 }
1532 };
1533 }
1534 }
1535
1536 /**
1537 * @throws NullPointerException {@inheritDoc}
1538 */
1539 @Override
1540 public void forEach(Consumer<? super E> action) {
1541 Objects.requireNonNull(action);
1542 final int expectedModCount = modCount;
1543 final Object[] es = elementData;
1544 final int size = this.size;
1545 for (int i = 0; modCount == expectedModCount && i < size; i++)
1546 action.accept(elementAt(es, i));
1547 if (modCount != expectedModCount)
1548 throw new ConcurrentModificationException();
1549 }
1550
1551 /**
1552 * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
1553 * and <em>fail-fast</em> {@link Spliterator} over the elements in this
1554 * list.
1555 *
1556 * <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
1557 * {@link Spliterator#SUBSIZED}, and {@link Spliterator#ORDERED}.
1558 * Overriding implementations should document the reporting of additional
1559 * characteristic values.
1560 *
1561 * @return a {@code Spliterator} over the elements in this list
1562 * @since 1.8
1563 */
1564 @Override
1565 public Spliterator<E> spliterator() {
1566 return new ArrayListSpliterator(0, -1, 0);
1567 }
1568
1569 /** Index-based split-by-two, lazily initialized Spliterator */
1570 final class ArrayListSpliterator implements Spliterator<E> {
1571
1572 /*
1573 * If ArrayLists were immutable, or structurally immutable (no
1574 * adds, removes, etc), we could implement their spliterators
1575 * with Arrays.spliterator. Instead we detect as much
1576 * interference during traversal as practical without
1577 * sacrificing much performance. We rely primarily on
1578 * modCounts. These are not guaranteed to detect concurrency
1579 * violations, and are sometimes overly conservative about
1580 * within-thread interference, but detect enough problems to
1581 * be worthwhile in practice. To carry this out, we (1) lazily
1582 * initialize fence and expectedModCount until the latest
1583 * point that we need to commit to the state we are checking
1584 * against; thus improving precision. (This doesn't apply to
1585 * SubLists, that create spliterators with current non-lazy
1586 * values). (2) We perform only a single
1587 * ConcurrentModificationException check at the end of forEach
1588 * (the most performance-sensitive method). When using forEach
1589 * (as opposed to iterators), we can normally only detect
1590 * interference after actions, not before. Further
1591 * CME-triggering checks apply to all other possible
1592 * violations of assumptions for example null or too-small
1593 * elementData array given its size(), that could only have
1594 * occurred due to interference. This allows the inner loop
1595 * of forEach to run without any further checks, and
1596 * simplifies lambda-resolution. While this does entail a
1597 * number of checks, note that in the common case of
1598 * list.stream().forEach(a), no checks or other computation
1599 * occur anywhere other than inside forEach itself. The other
1600 * less-often-used methods cannot take advantage of most of
1601 * these streamlinings.
1602 */
1603
1604 private int index; // current index, modified on advance/split
1605 private int fence; // -1 until used; then one past last index
1606 private int expectedModCount; // initialized when fence set
1607
1608 /** Creates new spliterator covering the given range. */
1609 ArrayListSpliterator(int origin, int fence, int expectedModCount) {
1610 this.index = origin;
1611 this.fence = fence;
1612 this.expectedModCount = expectedModCount;
1613 }
1614
1615 private int getFence() { // initialize fence to size on first use
1616 int hi; // (a specialized variant appears in method forEach)
1617 if ((hi = fence) < 0) {
1618 expectedModCount = modCount;
1619 hi = fence = size;
1620 }
1621 return hi;
1622 }
1623
1624 public ArrayListSpliterator trySplit() {
1625 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1626 return (lo >= mid) ? null : // divide range in half unless too small
1627 new ArrayListSpliterator(lo, index = mid, expectedModCount);
1628 }
1629
1630 public boolean tryAdvance(Consumer<? super E> action) {
1631 if (action == null)
1632 throw new NullPointerException();
1633 int hi = getFence(), i = index;
1634 if (i < hi) {
1635 index = i + 1;
1636 @SuppressWarnings("unchecked") E e = (E)elementData[i];
1637 action.accept(e);
1638 if (modCount != expectedModCount)
1639 throw new ConcurrentModificationException();
1640 return true;
1641 }
1642 return false;
1643 }
1644
1645 public void forEachRemaining(Consumer<? super E> action) {
1646 int i, hi, mc; // hoist accesses and checks from loop
1647 Object[] a;
1648 if (action == null)
1649 throw new NullPointerException();
1650 if ((a = elementData) != null) {
1651 if ((hi = fence) < 0) {
1652 mc = modCount;
1653 hi = size;
1654 }
1655 else
1656 mc = expectedModCount;
1657 if ((i = index) >= 0 && (index = hi) <= a.length) {
1658 for (; i < hi; ++i) {
1659 @SuppressWarnings("unchecked") E e = (E) a[i];
1660 action.accept(e);
1661 }
1662 if (modCount == mc)
1663 return;
1664 }
1665 }
1666 throw new ConcurrentModificationException();
1667 }
1668
1669 public long estimateSize() {
1670 return getFence() - index;
1671 }
1672
1673 public int characteristics() {
1674 return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
1675 }
1676 }
1677
1678 // A tiny bit set implementation
1679
1680 private static long[] nBits(int n) {
1681 return new long[((n - 1) >> 6) + 1];
1682 }
1683 private static void setBit(long[] bits, int i) {
1684 bits[i >> 6] |= 1L << i;
1685 }
1686 private static boolean isClear(long[] bits, int i) {
1687 return (bits[i >> 6] & (1L << i)) == 0;
1688 }
1689
1690 /**
1691 * @throws NullPointerException {@inheritDoc}
1692 */
1693 @Override
1694 public boolean removeIf(Predicate<? super E> filter) {
1695 return removeIf(filter, 0, size);
1696 }
1697
1698 /**
1699 * Removes all elements satisfying the given predicate, from index
1700 * i (inclusive) to index end (exclusive).
1701 */
1702 boolean removeIf(Predicate<? super E> filter, int i, final int end) {
1703 Objects.requireNonNull(filter);
1704 int expectedModCount = modCount;
1705 final Object[] es = elementData;
1706 // Optimize for initial run of survivors
1707 for (; i < end && !filter.test(elementAt(es, i)); i++)
1708 ;
1709 // Tolerate predicates that reentrantly access the collection for
1710 // read (but writers still get CME), so traverse once to find
1711 // elements to delete, a second pass to physically expunge.
1712 if (i < end) {
1713 final int beg = i;
1714 final long[] deathRow = nBits(end - beg);
1715 deathRow[0] = 1L; // set bit 0
1716 for (i = beg + 1; i < end; i++)
1717 if (filter.test(elementAt(es, i)))
1718 setBit(deathRow, i - beg);
1719 if (modCount != expectedModCount)
1720 throw new ConcurrentModificationException();
1721 modCount++;
1722 int w = beg;
1723 for (i = beg; i < end; i++)
1724 if (isClear(deathRow, i - beg))
1725 es[w++] = es[i];
1726 shiftTailOverGap(es, w, end);
1727 return true;
1728 } else {
1729 if (modCount != expectedModCount)
1730 throw new ConcurrentModificationException();
1731 return false;
1732 }
1733 }
1734
1735 @Override
1736 public void replaceAll(UnaryOperator<E> operator) {
1737 replaceAllRange(operator, 0, size);
1738 modCount++;
1739 }
1740
1741 private void replaceAllRange(UnaryOperator<E> operator, int i, int end) {
1742 Objects.requireNonNull(operator);
1743 final int expectedModCount = modCount;
1744 final Object[] es = elementData;
1745 for (; modCount == expectedModCount && i < end; i++)
1746 es[i] = operator.apply(elementAt(es, i));
1747 if (modCount != expectedModCount)
1748 throw new ConcurrentModificationException();
1749 }
1750
1751 @Override
1752 @SuppressWarnings("unchecked")
1753 public void sort(Comparator<? super E> c) {
1754 final int expectedModCount = modCount;
1755 Arrays.sort((E[]) elementData, 0, size, c);
1756 if (modCount != expectedModCount)
1757 throw new ConcurrentModificationException();
1758 modCount++;
1759 }
1760
1761 void checkInvariants() {
1762 // assert size >= 0;
1763 // assert size == elementData.length || elementData[size] == null;
1764 }
1765 }