1 /*
2 * Copyright (c) 1997, 2017, 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 sun.misc.SharedSecrets;
32
33 /**
34 * Resizable-array implementation of the <tt>List</tt> interface. Implements
35 * all optional list operations, and permits all elements, including
36 * <tt>null</tt>. In addition to implementing the <tt>List</tt> 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 * <tt>Vector</tt>, except that it is unsynchronized.)
40 *
41 * <p>The <tt>size</tt>, <tt>isEmpty</tt>, <tt>get</tt>, <tt>set</tt>,
42 * <tt>iterator</tt>, and <tt>listIterator</tt> operations run in constant
43 * time. The <tt>add</tt> 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 <tt>LinkedList</tt> implementation.
47 *
48 * <p>Each <tt>ArrayList</tt> 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 <tt>ArrayList</tt> instance
56 * before adding a large number of elements using the <tt>ensureCapacity</tt>
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 <tt>ArrayList</tt> 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><a name="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>:</a>
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}/../technotes/guides/collections/index.html">
96 * Java Collections Framework</a>.
97 *
98 * @author Josh Bloch
99 * @author Neal Gafter
100 * @see Collection
101 * @see List
102 * @see LinkedList
103 * @see Vector
104 * @since 1.2
105 */
106
107 public class ArrayList<E> extends AbstractList<E>
108 implements List<E>, RandomAccess, Cloneable, java.io.Serializable
109 {
110 private static final long serialVersionUID = 8683452581122892189L;
111
112 /**
113 * Default initial capacity.
114 */
115 private static final int DEFAULT_CAPACITY = 10;
116
117 /**
118 * Shared empty array instance used for empty instances.
119 */
120 private static final Object[] EMPTY_ELEMENTDATA = {};
121
122 /**
123 * Shared empty array instance used for default sized empty instances. We
124 * distinguish this from EMPTY_ELEMENTDATA to know how much to inflate when
125 * first element is added.
126 */
127 private static final Object[] DEFAULTCAPACITY_EMPTY_ELEMENTDATA = {};
128
129 /**
130 * The array buffer into which the elements of the ArrayList are stored.
131 * The capacity of the ArrayList is the length of this array buffer. Any
132 * empty ArrayList with elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA
133 * will be expanded to DEFAULT_CAPACITY when the first element is added.
134 */
135 transient Object[] elementData; // non-private to simplify nested class access
136
137 /**
138 * The size of the ArrayList (the number of elements it contains).
139 *
140 * @serial
141 */
142 private int size;
143
144 /**
145 * Constructs an empty list with the specified initial capacity.
146 *
147 * @param initialCapacity the initial capacity of the list
148 * @throws IllegalArgumentException if the specified initial capacity
149 * is negative
150 */
151 public ArrayList(int initialCapacity) {
152 if (initialCapacity > 0) {
153 this.elementData = new Object[initialCapacity];
154 } else if (initialCapacity == 0) {
155 this.elementData = EMPTY_ELEMENTDATA;
156 } else {
157 throw new IllegalArgumentException("Illegal Capacity: "+
158 initialCapacity);
159 }
160 }
161
162 /**
163 * Constructs an empty list with an initial capacity of ten.
164 */
165 public ArrayList() {
166 this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA;
167 }
168
169 /**
170 * Constructs a list containing the elements of the specified
171 * collection, in the order they are returned by the collection's
172 * iterator.
173 *
174 * @param c the collection whose elements are to be placed into this list
175 * @throws NullPointerException if the specified collection is null
176 */
177 public ArrayList(Collection<? extends E> c) {
178 elementData = c.toArray();
179 if ((size = elementData.length) != 0) {
180 // c.toArray might (incorrectly) not return Object[] (see 6260652)
181 if (elementData.getClass() != Object[].class)
182 elementData = Arrays.copyOf(elementData, size, Object[].class);
183 } else {
184 // replace with empty array.
185 this.elementData = EMPTY_ELEMENTDATA;
186 }
187 }
188
189 /**
190 * Trims the capacity of this <tt>ArrayList</tt> instance to be the
191 * list's current size. An application can use this operation to minimize
192 * the storage of an <tt>ArrayList</tt> instance.
193 */
194 public void trimToSize() {
195 modCount++;
196 if (size < elementData.length) {
197 elementData = (size == 0)
198 ? EMPTY_ELEMENTDATA
199 : Arrays.copyOf(elementData, size);
200 }
201 }
202
203 /**
204 * Increases the capacity of this <tt>ArrayList</tt> instance, if
205 * necessary, to ensure that it can hold at least the number of elements
206 * specified by the minimum capacity argument.
207 *
208 * @param minCapacity the desired minimum capacity
209 */
210 public void ensureCapacity(int minCapacity) {
211 int minExpand = (elementData != DEFAULTCAPACITY_EMPTY_ELEMENTDATA)
212 // any size if not default element table
213 ? 0
214 // larger than default for default empty table. It's already
215 // supposed to be at default size.
216 : DEFAULT_CAPACITY;
217
218 if (minCapacity > minExpand) {
219 ensureExplicitCapacity(minCapacity);
220 }
221 }
222
223 private static int calculateCapacity(Object[] elementData, int minCapacity) {
224 if (elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA) {
225 return Math.max(DEFAULT_CAPACITY, minCapacity);
226 }
227 return minCapacity;
228 }
229
230 private void ensureCapacityInternal(int minCapacity) {
231 ensureExplicitCapacity(calculateCapacity(elementData, minCapacity));
232 }
233
234 private void ensureExplicitCapacity(int minCapacity) {
235 modCount++;
236
237 // overflow-conscious code
238 if (minCapacity - elementData.length > 0)
239 grow(minCapacity);
240 }
241
242 /**
243 * The maximum size of array to allocate.
244 * Some VMs reserve some header words in an array.
245 * Attempts to allocate larger arrays may result in
246 * OutOfMemoryError: Requested array size exceeds VM limit
247 */
248 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
249
250 /**
251 * Increases the capacity to ensure that it can hold at least the
252 * number of elements specified by the minimum capacity argument.
253 *
254 * @param minCapacity the desired minimum capacity
255 */
256 private void grow(int minCapacity) {
257 // overflow-conscious code
258 int oldCapacity = elementData.length;
259 int newCapacity = oldCapacity + (oldCapacity >> 1);
260 if (newCapacity - minCapacity < 0)
261 newCapacity = minCapacity;
262 if (newCapacity - MAX_ARRAY_SIZE > 0)
263 newCapacity = hugeCapacity(minCapacity);
264 // minCapacity is usually close to size, so this is a win:
265 elementData = Arrays.copyOf(elementData, newCapacity);
266 }
267
268 private static int hugeCapacity(int minCapacity) {
269 if (minCapacity < 0) // overflow
270 throw new OutOfMemoryError();
271 return (minCapacity > MAX_ARRAY_SIZE) ?
272 Integer.MAX_VALUE :
273 MAX_ARRAY_SIZE;
274 }
275
276 /**
277 * Returns the number of elements in this list.
278 *
279 * @return the number of elements in this list
280 */
281 public int size() {
282 return size;
283 }
284
285 /**
286 * Returns <tt>true</tt> if this list contains no elements.
287 *
288 * @return <tt>true</tt> if this list contains no elements
289 */
290 public boolean isEmpty() {
291 return size == 0;
292 }
293
294 /**
295 * Returns <tt>true</tt> if this list contains the specified element.
296 * More formally, returns <tt>true</tt> if and only if this list contains
297 * at least one element <tt>e</tt> such that
298 * <tt>(o==null ? e==null : o.equals(e))</tt>.
299 *
300 * @param o element whose presence in this list is to be tested
301 * @return <tt>true</tt> if this list contains the specified element
302 */
303 public boolean contains(Object o) {
304 return indexOf(o) >= 0;
305 }
306
307 /**
308 * Returns the index of the first occurrence of the specified element
309 * in this list, or -1 if this list does not contain the element.
310 * More formally, returns the lowest index <tt>i</tt> such that
311 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
312 * or -1 if there is no such index.
313 */
314 public int indexOf(Object o) {
315 if (o == null) {
316 for (int i = 0; i < size; i++)
317 if (elementData[i]==null)
318 return i;
319 } else {
320 for (int i = 0; i < size; i++)
321 if (o.equals(elementData[i]))
322 return i;
323 }
324 return -1;
325 }
326
327 /**
328 * Returns the index of the last occurrence of the specified element
329 * in this list, or -1 if this list does not contain the element.
330 * More formally, returns the highest index <tt>i</tt> such that
331 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
332 * or -1 if there is no such index.
333 */
334 public int lastIndexOf(Object o) {
335 if (o == null) {
336 for (int i = size-1; i >= 0; i--)
337 if (elementData[i]==null)
338 return i;
339 } else {
340 for (int i = size-1; i >= 0; i--)
341 if (o.equals(elementData[i]))
342 return i;
343 }
344 return -1;
345 }
346
347 /**
348 * Returns a shallow copy of this <tt>ArrayList</tt> instance. (The
349 * elements themselves are not copied.)
350 *
351 * @return a clone of this <tt>ArrayList</tt> instance
352 */
353 public Object clone() {
354 try {
355 ArrayList<?> v = (ArrayList<?>) super.clone();
356 v.elementData = Arrays.copyOf(elementData, size);
357 v.modCount = 0;
358 return v;
359 } catch (CloneNotSupportedException e) {
360 // this shouldn't happen, since we are Cloneable
361 throw new InternalError(e);
362 }
363 }
364
365 /**
366 * Returns an array containing all of the elements in this list
367 * in proper sequence (from first to last element).
368 *
369 * <p>The returned array will be "safe" in that no references to it are
370 * maintained by this list. (In other words, this method must allocate
371 * a new array). The caller is thus free to modify the returned array.
372 *
373 * <p>This method acts as bridge between array-based and collection-based
374 * APIs.
375 *
376 * @return an array containing all of the elements in this list in
377 * proper sequence
378 */
379 public Object[] toArray() {
380 return Arrays.copyOf(elementData, size);
381 }
382
383 /**
384 * Returns an array containing all of the elements in this list in proper
385 * sequence (from first to last element); the runtime type of the returned
386 * array is that of the specified array. If the list fits in the
387 * specified array, it is returned therein. Otherwise, a new array is
388 * allocated with the runtime type of the specified array and the size of
389 * this list.
390 *
391 * <p>If the list fits in the specified array with room to spare
392 * (i.e., the array has more elements than the list), the element in
393 * the array immediately following the end of the collection is set to
394 * <tt>null</tt>. (This is useful in determining the length of the
395 * list <i>only</i> if the caller knows that the list does not contain
396 * any null elements.)
397 *
398 * @param a the array into which the elements of the list are to
399 * be stored, if it is big enough; otherwise, a new array of the
400 * same runtime type is allocated for this purpose.
401 * @return an array containing the elements of the list
402 * @throws ArrayStoreException if the runtime type of the specified array
403 * is not a supertype of the runtime type of every element in
404 * this list
405 * @throws NullPointerException if the specified array is null
406 */
407 @SuppressWarnings("unchecked")
408 public <T> T[] toArray(T[] a) {
409 if (a.length < size)
410 // Make a new array of a's runtime type, but my contents:
411 return (T[]) Arrays.copyOf(elementData, size, a.getClass());
412 System.arraycopy(elementData, 0, a, 0, size);
413 if (a.length > size)
414 a[size] = null;
415 return a;
416 }
417
418 // Positional Access Operations
419
420 @SuppressWarnings("unchecked")
421 E elementData(int index) {
422 return (E) elementData[index];
423 }
424
425 /**
426 * Returns the element at the specified position in this list.
427 *
428 * @param index index of the element to return
429 * @return the element at the specified position in this list
430 * @throws IndexOutOfBoundsException {@inheritDoc}
431 */
432 public E get(int index) {
433 rangeCheck(index);
434
435 return elementData(index);
436 }
437
438 /**
439 * Replaces the element at the specified position in this list with
440 * the specified element.
441 *
442 * @param index index of the element to replace
443 * @param element element to be stored at the specified position
444 * @return the element previously at the specified position
445 * @throws IndexOutOfBoundsException {@inheritDoc}
446 */
447 public E set(int index, E element) {
448 rangeCheck(index);
449
450 E oldValue = elementData(index);
451 elementData[index] = element;
452 return oldValue;
453 }
454
455 /**
456 * Appends the specified element to the end of this list.
457 *
458 * @param e element to be appended to this list
459 * @return <tt>true</tt> (as specified by {@link Collection#add})
460 */
461 public boolean add(E e) {
462 ensureCapacityInternal(size + 1); // Increments modCount!!
463 elementData[size++] = e;
464 return true;
465 }
466
467 /**
468 * Inserts the specified element at the specified position in this
469 * list. Shifts the element currently at that position (if any) and
470 * any subsequent elements to the right (adds one to their indices).
471 *
472 * @param index index at which the specified element is to be inserted
473 * @param element element to be inserted
474 * @throws IndexOutOfBoundsException {@inheritDoc}
475 */
476 public void add(int index, E element) {
477 rangeCheckForAdd(index);
478
479 ensureCapacityInternal(size + 1); // Increments modCount!!
480 System.arraycopy(elementData, index, elementData, index + 1,
481 size - index);
482 elementData[index] = element;
483 size++;
484 }
485
486 /**
487 * Removes the element at the specified position in this list.
488 * Shifts any subsequent elements to the left (subtracts one from their
489 * indices).
490 *
491 * @param index the index of the element to be removed
492 * @return the element that was removed from the list
493 * @throws IndexOutOfBoundsException {@inheritDoc}
494 */
495 public E remove(int index) {
496 rangeCheck(index);
497
498 modCount++;
499 E oldValue = elementData(index);
500
501 int numMoved = size - index - 1;
502 if (numMoved > 0)
503 System.arraycopy(elementData, index+1, elementData, index,
504 numMoved);
505 elementData[--size] = null; // clear to let GC do its work
506
507 return oldValue;
508 }
509
510 /**
511 * Removes the first occurrence of the specified element from this list,
512 * if it is present. If the list does not contain the element, it is
513 * unchanged. More formally, removes the element with the lowest index
514 * <tt>i</tt> such that
515 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>
516 * (if such an element exists). Returns <tt>true</tt> if this list
517 * contained the specified element (or equivalently, if this list
518 * changed as a result of the call).
519 *
520 * @param o element to be removed from this list, if present
521 * @return <tt>true</tt> if this list contained the specified element
522 */
523 public boolean remove(Object o) {
524 if (o == null) {
525 for (int index = 0; index < size; index++)
526 if (elementData[index] == null) {
527 fastRemove(index);
528 return true;
529 }
530 } else {
531 for (int index = 0; index < size; index++)
532 if (o.equals(elementData[index])) {
533 fastRemove(index);
534 return true;
535 }
536 }
537 return false;
538 }
539
540 /*
541 * Private remove method that skips bounds checking and does not
542 * return the value removed.
543 */
544 private void fastRemove(int index) {
545 modCount++;
546 int numMoved = size - index - 1;
547 if (numMoved > 0)
548 System.arraycopy(elementData, index+1, elementData, index,
549 numMoved);
550 elementData[--size] = null; // clear to let GC do its work
551 }
552
553 /**
554 * Removes all of the elements from this list. The list will
555 * be empty after this call returns.
556 */
557 public void clear() {
558 modCount++;
559
560 // clear to let GC do its work
561 for (int i = 0; i < size; i++)
562 elementData[i] = null;
563
564 size = 0;
565 }
566
567 /**
568 * Appends all of the elements in the specified collection to the end of
569 * this list, in the order that they are returned by the
570 * specified collection's Iterator. The behavior of this operation is
571 * undefined if the specified collection is modified while the operation
572 * is in progress. (This implies that the behavior of this call is
573 * undefined if the specified collection is this list, and this
574 * list is nonempty.)
575 *
576 * @param c collection containing elements to be added to this list
577 * @return <tt>true</tt> if this list changed as a result of the call
578 * @throws NullPointerException if the specified collection is null
579 */
580 public boolean addAll(Collection<? extends E> c) {
581 Object[] a = c.toArray();
582 int numNew = a.length;
583 ensureCapacityInternal(size + numNew); // Increments modCount
584 System.arraycopy(a, 0, elementData, size, numNew);
585 size += numNew;
586 return numNew != 0;
587 }
588
589 /**
590 * Inserts all of the elements in the specified collection into this
591 * list, starting at the specified position. Shifts the element
592 * currently at that position (if any) and any subsequent elements to
593 * the right (increases their indices). The new elements will appear
594 * in the list in the order that they are returned by the
595 * specified collection's iterator.
596 *
597 * @param index index at which to insert the first element from the
598 * specified collection
599 * @param c collection containing elements to be added to this list
600 * @return <tt>true</tt> if this list changed as a result of the call
601 * @throws IndexOutOfBoundsException {@inheritDoc}
602 * @throws NullPointerException if the specified collection is null
603 */
604 public boolean addAll(int index, Collection<? extends E> c) {
605 rangeCheckForAdd(index);
606
607 Object[] a = c.toArray();
608 int numNew = a.length;
609 ensureCapacityInternal(size + numNew); // Increments modCount
610
611 int numMoved = size - index;
612 if (numMoved > 0)
613 System.arraycopy(elementData, index, elementData, index + numNew,
614 numMoved);
615
616 System.arraycopy(a, 0, elementData, index, numNew);
617 size += numNew;
618 return numNew != 0;
619 }
620
621 /**
622 * Removes from this list all of the elements whose index is between
623 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
624 * Shifts any succeeding elements to the left (reduces their index).
625 * This call shortens the list by {@code (toIndex - fromIndex)} elements.
626 * (If {@code toIndex==fromIndex}, this operation has no effect.)
627 *
628 * @throws IndexOutOfBoundsException if {@code fromIndex} or
629 * {@code toIndex} is out of range
630 * ({@code fromIndex < 0 ||
631 * fromIndex >= size() ||
632 * toIndex > size() ||
633 * toIndex < fromIndex})
634 */
635 protected void removeRange(int fromIndex, int toIndex) {
636 modCount++;
637 int numMoved = size - toIndex;
638 System.arraycopy(elementData, toIndex, elementData, fromIndex,
639 numMoved);
640
641 // clear to let GC do its work
642 int newSize = size - (toIndex-fromIndex);
643 for (int i = newSize; i < size; i++) {
644 elementData[i] = null;
645 }
646 size = newSize;
647 }
648
649 /**
650 * Checks if the given index is in range. If not, throws an appropriate
651 * runtime exception. This method does *not* check if the index is
652 * negative: It is always used immediately prior to an array access,
653 * which throws an ArrayIndexOutOfBoundsException if index is negative.
654 */
655 private void rangeCheck(int index) {
656 if (index >= size)
657 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
658 }
659
660 /**
661 * A version of rangeCheck used by add and addAll.
662 */
663 private void rangeCheckForAdd(int index) {
664 if (index > size || index < 0)
665 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
666 }
667
668 /**
669 * Constructs an IndexOutOfBoundsException detail message.
670 * Of the many possible refactorings of the error handling code,
671 * this "outlining" performs best with both server and client VMs.
672 */
673 private String outOfBoundsMsg(int index) {
674 return "Index: "+index+", Size: "+size;
675 }
676
677 /**
678 * Removes from this list all of its elements that are contained in the
679 * specified collection.
680 *
681 * @param c collection containing elements to be removed from this list
682 * @return {@code true} if this list changed as a result of the call
683 * @throws ClassCastException if the class of an element of this list
684 * is incompatible with the specified collection
685 * (<a href="Collection.html#optional-restrictions">optional</a>)
686 * @throws NullPointerException if this list contains a null element and the
687 * specified collection does not permit null elements
688 * (<a href="Collection.html#optional-restrictions">optional</a>),
689 * or if the specified collection is null
690 * @see Collection#contains(Object)
691 */
692 public boolean removeAll(Collection<?> c) {
693 Objects.requireNonNull(c);
694 return batchRemove(c, false);
695 }
696
697 /**
698 * Retains only the elements in this list that are contained in the
699 * specified collection. In other words, removes from this list all
700 * of its elements that are not contained in the specified collection.
701 *
702 * @param c collection containing elements to be retained in this list
703 * @return {@code true} if this list changed as a result of the call
704 * @throws ClassCastException if the class of an element of this list
705 * is incompatible with the specified collection
706 * (<a href="Collection.html#optional-restrictions">optional</a>)
707 * @throws NullPointerException if this list contains a null element and the
708 * specified collection does not permit null elements
709 * (<a href="Collection.html#optional-restrictions">optional</a>),
710 * or if the specified collection is null
711 * @see Collection#contains(Object)
712 */
713 public boolean retainAll(Collection<?> c) {
714 Objects.requireNonNull(c);
715 return batchRemove(c, true);
716 }
717
718 private boolean batchRemove(Collection<?> c, boolean complement) {
719 final Object[] elementData = this.elementData;
720 int r = 0, w = 0;
721 boolean modified = false;
722 try {
723 for (; r < size; r++)
724 if (c.contains(elementData[r]) == complement)
725 elementData[w++] = elementData[r];
726 } finally {
727 // Preserve behavioral compatibility with AbstractCollection,
728 // even if c.contains() throws.
729 if (r != size) {
730 System.arraycopy(elementData, r,
731 elementData, w,
732 size - r);
733 w += size - r;
734 }
735 if (w != size) {
736 // clear to let GC do its work
737 for (int i = w; i < size; i++)
738 elementData[i] = null;
739 modCount += size - w;
740 size = w;
741 modified = true;
742 }
743 }
744 return modified;
745 }
746
747 /**
748 * Save the state of the <tt>ArrayList</tt> instance to a stream (that
749 * is, serialize it).
750 *
751 * @serialData The length of the array backing the <tt>ArrayList</tt>
752 * instance is emitted (int), followed by all of its elements
753 * (each an <tt>Object</tt>) in the proper order.
754 */
755 private void writeObject(java.io.ObjectOutputStream s)
756 throws java.io.IOException{
757 // Write out element count, and any hidden stuff
758 int expectedModCount = modCount;
759 s.defaultWriteObject();
760
761 // Write out size as capacity for behavioural compatibility with clone()
762 s.writeInt(size);
763
764 // Write out all elements in the proper order.
765 for (int i=0; i<size; i++) {
766 s.writeObject(elementData[i]);
767 }
768
769 if (modCount != expectedModCount) {
770 throw new ConcurrentModificationException();
771 }
772 }
773
774 /**
775 * Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
776 * deserialize it).
777 */
778 private void readObject(java.io.ObjectInputStream s)
779 throws java.io.IOException, ClassNotFoundException {
780 elementData = EMPTY_ELEMENTDATA;
781
782 // Read in size, and any hidden stuff
783 s.defaultReadObject();
784
785 // Read in capacity
786 s.readInt(); // ignored
787
788 if (size > 0) {
789 // be like clone(), allocate array based upon size not capacity
790 int capacity = calculateCapacity(elementData, size);
791 SharedSecrets.getJavaOISAccess().checkArray(s, Object[].class, capacity);
792 ensureCapacityInternal(size);
793
794 Object[] a = elementData;
795 // Read in all elements in the proper order.
796 for (int i=0; i<size; i++) {
797 a[i] = s.readObject();
798 }
799 }
800 }
801
802 /**
803 * Returns a list iterator over the elements in this list (in proper
804 * sequence), starting at the specified position in the list.
805 * The specified index indicates the first element that would be
806 * returned by an initial call to {@link ListIterator#next next}.
807 * An initial call to {@link ListIterator#previous previous} would
808 * return the element with the specified index minus one.
809 *
810 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
811 *
812 * @throws IndexOutOfBoundsException {@inheritDoc}
813 */
814 public ListIterator<E> listIterator(int index) {
815 if (index < 0 || index > size)
816 throw new IndexOutOfBoundsException("Index: "+index);
817 return new ListItr(index);
818 }
819
820 /**
821 * Returns a list iterator over the elements in this list (in proper
822 * sequence).
823 *
824 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
825 *
826 * @see #listIterator(int)
827 */
828 public ListIterator<E> listIterator() {
829 return new ListItr(0);
830 }
831
832 /**
833 * Returns an iterator over the elements in this list in proper sequence.
834 *
835 * <p>The returned iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
836 *
837 * @return an iterator over the elements in this list in proper sequence
838 */
839 public Iterator<E> iterator() {
840 return new Itr();
841 }
842
843 /**
844 * An optimized version of AbstractList.Itr
845 */
846 private class Itr implements Iterator<E> {
847 int cursor; // index of next element to return
848 int lastRet = -1; // index of last element returned; -1 if no such
849 int expectedModCount = modCount;
850
851 public boolean hasNext() {
852 return cursor != size;
853 }
854
855 @SuppressWarnings("unchecked")
856 public E next() {
857 checkForComodification();
858 int i = cursor;
859 if (i >= size)
860 throw new NoSuchElementException();
861 Object[] elementData = ArrayList.this.elementData;
862 if (i >= elementData.length)
863 throw new ConcurrentModificationException();
864 cursor = i + 1;
865 return (E) elementData[lastRet = i];
866 }
867
868 public void remove() {
869 if (lastRet < 0)
870 throw new IllegalStateException();
871 checkForComodification();
872
873 try {
874 ArrayList.this.remove(lastRet);
875 cursor = lastRet;
876 lastRet = -1;
877 expectedModCount = modCount;
878 } catch (IndexOutOfBoundsException ex) {
879 throw new ConcurrentModificationException();
880 }
881 }
882
883 @Override
884 @SuppressWarnings("unchecked")
885 public void forEachRemaining(Consumer<? super E> consumer) {
886 Objects.requireNonNull(consumer);
887 final int size = ArrayList.this.size;
888 int i = cursor;
889 if (i >= size) {
890 return;
891 }
892 final Object[] elementData = ArrayList.this.elementData;
893 if (i >= elementData.length) {
894 throw new ConcurrentModificationException();
895 }
896 while (i != size && modCount == expectedModCount) {
897 consumer.accept((E) elementData[i++]);
898 }
899 // update once at end of iteration to reduce heap write traffic
900 cursor = i;
901 lastRet = i - 1;
902 checkForComodification();
903 }
904
905 final void checkForComodification() {
906 if (modCount != expectedModCount)
907 throw new ConcurrentModificationException();
908 }
909 }
910
911 /**
912 * An optimized version of AbstractList.ListItr
913 */
914 private class ListItr extends Itr implements ListIterator<E> {
915 ListItr(int index) {
916 super();
917 cursor = index;
918 }
919
920 public boolean hasPrevious() {
921 return cursor != 0;
922 }
923
924 public int nextIndex() {
925 return cursor;
926 }
927
928 public int previousIndex() {
929 return cursor - 1;
930 }
931
932 @SuppressWarnings("unchecked")
933 public E previous() {
934 checkForComodification();
935 int i = cursor - 1;
936 if (i < 0)
937 throw new NoSuchElementException();
938 Object[] elementData = ArrayList.this.elementData;
939 if (i >= elementData.length)
940 throw new ConcurrentModificationException();
941 cursor = i;
942 return (E) elementData[lastRet = i];
943 }
944
945 public void set(E e) {
946 if (lastRet < 0)
947 throw new IllegalStateException();
948 checkForComodification();
949
950 try {
951 ArrayList.this.set(lastRet, e);
952 } catch (IndexOutOfBoundsException ex) {
953 throw new ConcurrentModificationException();
954 }
955 }
956
957 public void add(E e) {
958 checkForComodification();
959
960 try {
961 int i = cursor;
962 ArrayList.this.add(i, e);
963 cursor = i + 1;
964 lastRet = -1;
965 expectedModCount = modCount;
966 } catch (IndexOutOfBoundsException ex) {
967 throw new ConcurrentModificationException();
968 }
969 }
970 }
971
972 /**
973 * Returns a view of the portion of this list between the specified
974 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. (If
975 * {@code fromIndex} and {@code toIndex} are equal, the returned list is
976 * empty.) The returned list is backed by this list, so non-structural
977 * changes in the returned list are reflected in this list, and vice-versa.
978 * The returned list supports all of the optional list operations.
979 *
980 * <p>This method eliminates the need for explicit range operations (of
981 * the sort that commonly exist for arrays). Any operation that expects
982 * a list can be used as a range operation by passing a subList view
983 * instead of a whole list. For example, the following idiom
984 * removes a range of elements from a list:
985 * <pre>
986 * list.subList(from, to).clear();
987 * </pre>
988 * Similar idioms may be constructed for {@link #indexOf(Object)} and
989 * {@link #lastIndexOf(Object)}, and all of the algorithms in the
990 * {@link Collections} class can be applied to a subList.
991 *
992 * <p>The semantics of the list returned by this method become undefined if
993 * the backing list (i.e., this list) is <i>structurally modified</i> in
994 * any way other than via the returned list. (Structural modifications are
995 * those that change the size of this list, or otherwise perturb it in such
996 * a fashion that iterations in progress may yield incorrect results.)
997 *
998 * @throws IndexOutOfBoundsException {@inheritDoc}
999 * @throws IllegalArgumentException {@inheritDoc}
1000 */
1001 public List<E> subList(int fromIndex, int toIndex) {
1002 subListRangeCheck(fromIndex, toIndex, size);
1003 return new SubList(this, 0, fromIndex, toIndex);
1004 }
1005
1006 static void subListRangeCheck(int fromIndex, int toIndex, int size) {
1007 if (fromIndex < 0)
1008 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
1009 if (toIndex > size)
1010 throw new IndexOutOfBoundsException("toIndex = " + toIndex);
1011 if (fromIndex > toIndex)
1012 throw new IllegalArgumentException("fromIndex(" + fromIndex +
1013 ") > toIndex(" + toIndex + ")");
1014 }
1015
1016 private class SubList extends AbstractList<E> implements RandomAccess {
1017 private final AbstractList<E> parent;
1018 private final int parentOffset;
1019 private final int offset;
1020 int size;
1021
1022 SubList(AbstractList<E> parent,
1023 int offset, int fromIndex, int toIndex) {
1024 this.parent = parent;
1025 this.parentOffset = fromIndex;
1026 this.offset = offset + fromIndex;
1027 this.size = toIndex - fromIndex;
1028 this.modCount = ArrayList.this.modCount;
1029 }
1030
1031 public E set(int index, E e) {
1032 rangeCheck(index);
1033 checkForComodification();
1034 E oldValue = ArrayList.this.elementData(offset + index);
1035 ArrayList.this.elementData[offset + index] = e;
1036 return oldValue;
1037 }
1038
1039 public E get(int index) {
1040 rangeCheck(index);
1041 checkForComodification();
1042 return ArrayList.this.elementData(offset + index);
1043 }
1044
1045 public int size() {
1046 checkForComodification();
1047 return this.size;
1048 }
1049
1050 public void add(int index, E e) {
1051 rangeCheckForAdd(index);
1052 checkForComodification();
1053 parent.add(parentOffset + index, e);
1054 this.modCount = parent.modCount;
1055 this.size++;
1056 }
1057
1058 public E remove(int index) {
1059 rangeCheck(index);
1060 checkForComodification();
1061 E result = parent.remove(parentOffset + index);
1062 this.modCount = parent.modCount;
1063 this.size--;
1064 return result;
1065 }
1066
1067 protected void removeRange(int fromIndex, int toIndex) {
1068 checkForComodification();
1069 parent.removeRange(parentOffset + fromIndex,
1070 parentOffset + toIndex);
1071 this.modCount = parent.modCount;
1072 this.size -= toIndex - fromIndex;
1073 }
1074
1075 public boolean addAll(Collection<? extends E> c) {
1076 return addAll(this.size, c);
1077 }
1078
1079 public boolean addAll(int index, Collection<? extends E> c) {
1080 rangeCheckForAdd(index);
1081 int cSize = c.size();
1082 if (cSize==0)
1083 return false;
1084
1085 checkForComodification();
1086 parent.addAll(parentOffset + index, c);
1087 this.modCount = parent.modCount;
1088 this.size += cSize;
1089 return true;
1090 }
1091
1092 public Iterator<E> iterator() {
1093 return listIterator();
1094 }
1095
1096 public ListIterator<E> listIterator(final int index) {
1097 checkForComodification();
1098 rangeCheckForAdd(index);
1099 final int offset = this.offset;
1100
1101 return new ListIterator<E>() {
1102 int cursor = index;
1103 int lastRet = -1;
1104 int expectedModCount = ArrayList.this.modCount;
1105
1106 public boolean hasNext() {
1107 return cursor != SubList.this.size;
1108 }
1109
1110 @SuppressWarnings("unchecked")
1111 public E next() {
1112 checkForComodification();
1113 int i = cursor;
1114 if (i >= SubList.this.size)
1115 throw new NoSuchElementException();
1116 Object[] elementData = ArrayList.this.elementData;
1117 if (offset + i >= elementData.length)
1118 throw new ConcurrentModificationException();
1119 cursor = i + 1;
1120 return (E) elementData[offset + (lastRet = i)];
1121 }
1122
1123 public boolean hasPrevious() {
1124 return cursor != 0;
1125 }
1126
1127 @SuppressWarnings("unchecked")
1128 public E previous() {
1129 checkForComodification();
1130 int i = cursor - 1;
1131 if (i < 0)
1132 throw new NoSuchElementException();
1133 Object[] elementData = ArrayList.this.elementData;
1134 if (offset + i >= elementData.length)
1135 throw new ConcurrentModificationException();
1136 cursor = i;
1137 return (E) elementData[offset + (lastRet = i)];
1138 }
1139
1140 @SuppressWarnings("unchecked")
1141 public void forEachRemaining(Consumer<? super E> consumer) {
1142 Objects.requireNonNull(consumer);
1143 final int size = SubList.this.size;
1144 int i = cursor;
1145 if (i >= size) {
1146 return;
1147 }
1148 final Object[] elementData = ArrayList.this.elementData;
1149 if (offset + i >= elementData.length) {
1150 throw new ConcurrentModificationException();
1151 }
1152 while (i != size && modCount == expectedModCount) {
1153 consumer.accept((E) elementData[offset + (i++)]);
1154 }
1155 // update once at end of iteration to reduce heap write traffic
1156 lastRet = cursor = i;
1157 checkForComodification();
1158 }
1159
1160 public int nextIndex() {
1161 return cursor;
1162 }
1163
1164 public int previousIndex() {
1165 return cursor - 1;
1166 }
1167
1168 public void remove() {
1169 if (lastRet < 0)
1170 throw new IllegalStateException();
1171 checkForComodification();
1172
1173 try {
1174 SubList.this.remove(lastRet);
1175 cursor = lastRet;
1176 lastRet = -1;
1177 expectedModCount = ArrayList.this.modCount;
1178 } catch (IndexOutOfBoundsException ex) {
1179 throw new ConcurrentModificationException();
1180 }
1181 }
1182
1183 public void set(E e) {
1184 if (lastRet < 0)
1185 throw new IllegalStateException();
1186 checkForComodification();
1187
1188 try {
1189 ArrayList.this.set(offset + lastRet, e);
1190 } catch (IndexOutOfBoundsException ex) {
1191 throw new ConcurrentModificationException();
1192 }
1193 }
1194
1195 public void add(E e) {
1196 checkForComodification();
1197
1198 try {
1199 int i = cursor;
1200 SubList.this.add(i, e);
1201 cursor = i + 1;
1202 lastRet = -1;
1203 expectedModCount = ArrayList.this.modCount;
1204 } catch (IndexOutOfBoundsException ex) {
1205 throw new ConcurrentModificationException();
1206 }
1207 }
1208
1209 final void checkForComodification() {
1210 if (expectedModCount != ArrayList.this.modCount)
1211 throw new ConcurrentModificationException();
1212 }
1213 };
1214 }
1215
1216 public List<E> subList(int fromIndex, int toIndex) {
1217 subListRangeCheck(fromIndex, toIndex, size);
1218 return new SubList(this, offset, fromIndex, toIndex);
1219 }
1220
1221 private void rangeCheck(int index) {
1222 if (index < 0 || index >= this.size)
1223 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
1224 }
1225
1226 private void rangeCheckForAdd(int index) {
1227 if (index < 0 || index > this.size)
1228 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
1229 }
1230
1231 private String outOfBoundsMsg(int index) {
1232 return "Index: "+index+", Size: "+this.size;
1233 }
1234
1235 private void checkForComodification() {
1236 if (ArrayList.this.modCount != this.modCount)
1237 throw new ConcurrentModificationException();
1238 }
1239
1240 public Spliterator<E> spliterator() {
1241 checkForComodification();
1242 return new ArrayListSpliterator<E>(ArrayList.this, offset,
1243 offset + this.size, this.modCount);
1244 }
1245 }
1246
1247 @Override
1248 public void forEach(Consumer<? super E> action) {
1249 Objects.requireNonNull(action);
1250 final int expectedModCount = modCount;
1251 @SuppressWarnings("unchecked")
1252 final E[] elementData = (E[]) this.elementData;
1253 final int size = this.size;
1254 for (int i=0; modCount == expectedModCount && i < size; i++) {
1255 action.accept(elementData[i]);
1256 }
1257 if (modCount != expectedModCount) {
1258 throw new ConcurrentModificationException();
1259 }
1260 }
1261
1262 /**
1263 * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
1264 * and <em>fail-fast</em> {@link Spliterator} over the elements in this
1265 * list.
1266 *
1267 * <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
1268 * {@link Spliterator#SUBSIZED}, and {@link Spliterator#ORDERED}.
1269 * Overriding implementations should document the reporting of additional
1270 * characteristic values.
1271 *
1272 * @return a {@code Spliterator} over the elements in this list
1273 * @since 1.8
1274 */
1275 @Override
1276 public Spliterator<E> spliterator() {
1277 return new ArrayListSpliterator<>(this, 0, -1, 0);
1278 }
1279
1280 /** Index-based split-by-two, lazily initialized Spliterator */
1281 static final class ArrayListSpliterator<E> implements Spliterator<E> {
1282
1283 /*
1284 * If ArrayLists were immutable, or structurally immutable (no
1285 * adds, removes, etc), we could implement their spliterators
1286 * with Arrays.spliterator. Instead we detect as much
1287 * interference during traversal as practical without
1288 * sacrificing much performance. We rely primarily on
1289 * modCounts. These are not guaranteed to detect concurrency
1290 * violations, and are sometimes overly conservative about
1291 * within-thread interference, but detect enough problems to
1292 * be worthwhile in practice. To carry this out, we (1) lazily
1293 * initialize fence and expectedModCount until the latest
1294 * point that we need to commit to the state we are checking
1295 * against; thus improving precision. (This doesn't apply to
1296 * SubLists, that create spliterators with current non-lazy
1297 * values). (2) We perform only a single
1298 * ConcurrentModificationException check at the end of forEach
1299 * (the most performance-sensitive method). When using forEach
1300 * (as opposed to iterators), we can normally only detect
1301 * interference after actions, not before. Further
1302 * CME-triggering checks apply to all other possible
1303 * violations of assumptions for example null or too-small
1304 * elementData array given its size(), that could only have
1305 * occurred due to interference. This allows the inner loop
1306 * of forEach to run without any further checks, and
1307 * simplifies lambda-resolution. While this does entail a
1308 * number of checks, note that in the common case of
1309 * list.stream().forEach(a), no checks or other computation
1310 * occur anywhere other than inside forEach itself. The other
1311 * less-often-used methods cannot take advantage of most of
1312 * these streamlinings.
1313 */
1314
1315 private final ArrayList<E> list;
1316 private int index; // current index, modified on advance/split
1317 private int fence; // -1 until used; then one past last index
1318 private int expectedModCount; // initialized when fence set
1319
1320 /** Create new spliterator covering the given range */
1321 ArrayListSpliterator(ArrayList<E> list, int origin, int fence,
1322 int expectedModCount) {
1323 this.list = list; // OK if null unless traversed
1324 this.index = origin;
1325 this.fence = fence;
1326 this.expectedModCount = expectedModCount;
1327 }
1328
1329 private int getFence() { // initialize fence to size on first use
1330 int hi; // (a specialized variant appears in method forEach)
1331 ArrayList<E> lst;
1332 if ((hi = fence) < 0) {
1333 if ((lst = list) == null)
1334 hi = fence = 0;
1335 else {
1336 expectedModCount = lst.modCount;
1337 hi = fence = lst.size;
1338 }
1339 }
1340 return hi;
1341 }
1342
1343 public ArrayListSpliterator<E> trySplit() {
1344 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1345 return (lo >= mid) ? null : // divide range in half unless too small
1346 new ArrayListSpliterator<E>(list, lo, index = mid,
1347 expectedModCount);
1348 }
1349
1350 public boolean tryAdvance(Consumer<? super E> action) {
1351 if (action == null)
1352 throw new NullPointerException();
1353 int hi = getFence(), i = index;
1354 if (i < hi) {
1355 index = i + 1;
1356 @SuppressWarnings("unchecked") E e = (E)list.elementData[i];
1357 action.accept(e);
1358 if (list.modCount != expectedModCount)
1359 throw new ConcurrentModificationException();
1360 return true;
1361 }
1362 return false;
1363 }
1364
1365 public void forEachRemaining(Consumer<? super E> action) {
1366 int i, hi, mc; // hoist accesses and checks from loop
1367 ArrayList<E> lst; Object[] a;
1368 if (action == null)
1369 throw new NullPointerException();
1370 if ((lst = list) != null && (a = lst.elementData) != null) {
1371 if ((hi = fence) < 0) {
1372 mc = lst.modCount;
1373 hi = lst.size;
1374 }
1375 else
1376 mc = expectedModCount;
1377 if ((i = index) >= 0 && (index = hi) <= a.length) {
1378 for (; i < hi; ++i) {
1379 @SuppressWarnings("unchecked") E e = (E) a[i];
1380 action.accept(e);
1381 }
1382 if (lst.modCount == mc)
1383 return;
1384 }
1385 }
1386 throw new ConcurrentModificationException();
1387 }
1388
1389 public long estimateSize() {
1390 return (long) (getFence() - index);
1391 }
1392
1393 public int characteristics() {
1394 return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
1395 }
1396 }
1397
1398 @Override
1399 public boolean removeIf(Predicate<? super E> filter) {
1400 Objects.requireNonNull(filter);
1401 // figure out which elements are to be removed
1402 // any exception thrown from the filter predicate at this stage
1403 // will leave the collection unmodified
1404 int removeCount = 0;
1405 final BitSet removeSet = new BitSet(size);
1406 final int expectedModCount = modCount;
1407 final int size = this.size;
1408 for (int i=0; modCount == expectedModCount && i < size; i++) {
1409 @SuppressWarnings("unchecked")
1410 final E element = (E) elementData[i];
1411 if (filter.test(element)) {
1412 removeSet.set(i);
1413 removeCount++;
1414 }
1415 }
1416 if (modCount != expectedModCount) {
1417 throw new ConcurrentModificationException();
1418 }
1419
1420 // shift surviving elements left over the spaces left by removed elements
1421 final boolean anyToRemove = removeCount > 0;
1422 if (anyToRemove) {
1423 final int newSize = size - removeCount;
1424 for (int i=0, j=0; (i < size) && (j < newSize); i++, j++) {
1425 i = removeSet.nextClearBit(i);
1426 elementData[j] = elementData[i];
1427 }
1428 for (int k=newSize; k < size; k++) {
1429 elementData[k] = null; // Let gc do its work
1430 }
1431 this.size = newSize;
1432 if (modCount != expectedModCount) {
1433 throw new ConcurrentModificationException();
1434 }
1435 modCount++;
1436 }
1437
1438 return anyToRemove;
1439 }
1440
1441 @Override
1442 @SuppressWarnings("unchecked")
1443 public void replaceAll(UnaryOperator<E> operator) {
1444 Objects.requireNonNull(operator);
1445 final int expectedModCount = modCount;
1446 final int size = this.size;
1447 for (int i=0; modCount == expectedModCount && i < size; i++) {
1448 elementData[i] = operator.apply((E) elementData[i]);
1449 }
1450 if (modCount != expectedModCount) {
1451 throw new ConcurrentModificationException();
1452 }
1453 modCount++;
1454 }
1455
1456 @Override
1457 @SuppressWarnings("unchecked")
1458 public void sort(Comparator<? super E> c) {
1459 final int expectedModCount = modCount;
1460 Arrays.sort((E[]) elementData, 0, size, c);
1461 if (modCount != expectedModCount) {
1462 throw new ConcurrentModificationException();
1463 }
1464 modCount++;
1465 }
1466 }