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 jdk.internal.misc.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/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 elementData = c.toArray();
180 if ((size = elementData.length) != 0) {
181 // defend against c.toArray (incorrectly) not returning Object[]
182 // (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652)
183 if (elementData.getClass() != Object[].class)
184 elementData = Arrays.copyOf(elementData, size, Object[].class);
185 } else {
186 // replace with empty array.
187 this.elementData = EMPTY_ELEMENTDATA;
188 }
189 }
190
191 /**
192 * Trims the capacity of this {@code ArrayList} instance to be the
193 * list's current size. An application can use this operation to minimize
194 * the storage of an {@code ArrayList} instance.
195 */
196 public void trimToSize() {
197 modCount++;
198 if (size < elementData.length) {
199 elementData = (size == 0)
200 ? EMPTY_ELEMENTDATA
201 : Arrays.copyOf(elementData, size);
202 }
203 }
204
205 /**
206 * Increases the capacity of this {@code ArrayList} instance, if
207 * necessary, to ensure that it can hold at least the number of elements
208 * specified by the minimum capacity argument.
209 *
210 * @param minCapacity the desired minimum capacity
211 */
212 public void ensureCapacity(int minCapacity) {
213 if (minCapacity > elementData.length
214 && !(elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA
215 && minCapacity <= DEFAULT_CAPACITY)) {
216 modCount++;
217 grow(minCapacity);
218 }
219 }
220
221 /**
222 * The maximum size of array to allocate (unless necessary).
223 * Some VMs reserve some header words in an array.
224 * Attempts to allocate larger arrays may result in
225 * OutOfMemoryError: Requested array size exceeds VM limit
226 */
227 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
228
229 /**
230 * Increases the capacity to ensure that it can hold at least the
231 * number of elements specified by the minimum capacity argument.
232 *
233 * @param minCapacity the desired minimum capacity
234 * @throws OutOfMemoryError if minCapacity is less than zero
235 */
236 private Object[] grow(int minCapacity) {
237 return elementData = Arrays.copyOf(elementData,
238 newCapacity(minCapacity));
239 }
240
241 private Object[] grow() {
242 return grow(size + 1);
243 }
244
245 /**
246 * Returns a capacity at least as large as the given minimum capacity.
247 * Returns the current capacity increased by 50% if that suffices.
248 * Will not return a capacity greater than MAX_ARRAY_SIZE unless
249 * the given minimum capacity is greater than MAX_ARRAY_SIZE.
250 *
251 * @param minCapacity the desired minimum capacity
252 * @throws OutOfMemoryError if minCapacity is less than zero
253 */
254 private int newCapacity(int minCapacity) {
255 // overflow-conscious code
256 int oldCapacity = elementData.length;
257 int newCapacity = oldCapacity + (oldCapacity >> 1);
258 if (newCapacity - minCapacity <= 0) {
259 if (elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA)
260 return Math.max(DEFAULT_CAPACITY, minCapacity);
261 if (minCapacity < 0) // overflow
262 throw new OutOfMemoryError();
263 return minCapacity;
264 }
265 return (newCapacity - MAX_ARRAY_SIZE <= 0)
266 ? newCapacity
267 : hugeCapacity(minCapacity);
268 }
269
270 private static int hugeCapacity(int minCapacity) {
271 if (minCapacity < 0) // overflow
272 throw new OutOfMemoryError();
273 return (minCapacity > MAX_ARRAY_SIZE)
274 ? Integer.MAX_VALUE
275 : MAX_ARRAY_SIZE;
276 }
277
278 /**
279 * Returns the number of elements in this list.
280 *
281 * @return the number of elements in this list
282 */
283 public int size() {
284 return size;
285 }
286
287 /**
288 * Returns {@code true} if this list contains no elements.
289 *
290 * @return {@code true} if this list contains no elements
291 */
292 public boolean isEmpty() {
293 return size == 0;
294 }
295
296 /**
297 * Returns {@code true} if this list contains the specified element.
298 * More formally, returns {@code true} if and only if this list contains
299 * at least one element {@code e} such that
300 * {@code Objects.equals(o, e)}.
301 *
302 * @param o element whose presence in this list is to be tested
303 * @return {@code true} if this list contains the specified element
304 */
305 public boolean contains(Object o) {
306 return indexOf(o) >= 0;
307 }
308
309 /**
310 * Returns the index of the first occurrence of the specified element
311 * in this list, or -1 if this list does not contain the element.
312 * More formally, returns the lowest index {@code i} such that
313 * {@code Objects.equals(o, get(i))},
314 * or -1 if there is no such index.
315 */
316 public int indexOf(Object o) {
317 if (o == null) {
318 for (int i = 0; i < size; i++)
319 if (elementData[i]==null)
320 return i;
321 } else {
322 for (int i = 0; i < size; i++)
323 if (o.equals(elementData[i]))
324 return i;
325 }
326 return -1;
327 }
328
329 /**
330 * Returns the index of the last occurrence of the specified element
331 * in this list, or -1 if this list does not contain the element.
332 * More formally, returns the highest index {@code i} such that
333 * {@code Objects.equals(o, get(i))},
334 * or -1 if there is no such index.
335 */
336 public int lastIndexOf(Object o) {
337 if (o == null) {
338 for (int i = size-1; i >= 0; i--)
339 if (elementData[i]==null)
340 return i;
341 } else {
342 for (int i = size-1; i >= 0; i--)
343 if (o.equals(elementData[i]))
344 return i;
345 }
346 return -1;
347 }
348
349 /**
350 * Returns a shallow copy of this {@code ArrayList} instance. (The
351 * elements themselves are not copied.)
352 *
353 * @return a clone of this {@code ArrayList} instance
354 */
355 public Object clone() {
356 try {
357 ArrayList<?> v = (ArrayList<?>) super.clone();
358 v.elementData = Arrays.copyOf(elementData, size);
359 v.modCount = 0;
360 return v;
361 } catch (CloneNotSupportedException e) {
362 // this shouldn't happen, since we are Cloneable
363 throw new InternalError(e);
364 }
365 }
366
367 /**
368 * Returns an array containing all of the elements in this list
369 * in proper sequence (from first to last element).
370 *
371 * <p>The returned array will be "safe" in that no references to it are
372 * maintained by this list. (In other words, this method must allocate
373 * a new array). The caller is thus free to modify the returned array.
374 *
375 * <p>This method acts as bridge between array-based and collection-based
376 * APIs.
377 *
378 * @return an array containing all of the elements in this list in
379 * proper sequence
380 */
381 public Object[] toArray() {
382 return Arrays.copyOf(elementData, size);
383 }
384
385 /**
386 * Returns an array containing all of the elements in this list in proper
387 * sequence (from first to last element); the runtime type of the returned
388 * array is that of the specified array. If the list fits in the
389 * specified array, it is returned therein. Otherwise, a new array is
390 * allocated with the runtime type of the specified array and the size of
391 * this list.
392 *
393 * <p>If the list fits in the specified array with room to spare
394 * (i.e., the array has more elements than the list), the element in
395 * the array immediately following the end of the collection is set to
396 * {@code null}. (This is useful in determining the length of the
397 * list <i>only</i> if the caller knows that the list does not contain
398 * any null elements.)
399 *
400 * @param a the array into which the elements of the list are to
401 * be stored, if it is big enough; otherwise, a new array of the
402 * same runtime type is allocated for this purpose.
403 * @return an array containing the elements of the list
404 * @throws ArrayStoreException if the runtime type of the specified array
405 * is not a supertype of the runtime type of every element in
406 * this list
407 * @throws NullPointerException if the specified array is null
408 */
409 @SuppressWarnings("unchecked")
410 public <T> T[] toArray(T[] a) {
411 if (a.length < size)
412 // Make a new array of a's runtime type, but my contents:
413 return (T[]) Arrays.copyOf(elementData, size, a.getClass());
414 System.arraycopy(elementData, 0, a, 0, size);
415 if (a.length > size)
416 a[size] = null;
417 return a;
418 }
419
420 // Positional Access Operations
421
422 @SuppressWarnings("unchecked")
423 E elementData(int index) {
424 return (E) elementData[index];
425 }
426
427 @SuppressWarnings("unchecked")
428 static <E> E elementAt(Object[] es, int index) {
429 return (E) es[index];
430 }
431
432 /**
433 * Returns the element at the specified position in this list.
434 *
435 * @param index index of the element to return
436 * @return the element at the specified position in this list
437 * @throws IndexOutOfBoundsException {@inheritDoc}
438 */
439 public E get(int index) {
440 Objects.checkIndex(index, size);
441 return elementData(index);
442 }
443
444 /**
445 * Replaces the element at the specified position in this list with
446 * the specified element.
447 *
448 * @param index index of the element to replace
449 * @param element element to be stored at the specified position
450 * @return the element previously at the specified position
451 * @throws IndexOutOfBoundsException {@inheritDoc}
452 */
453 public E set(int index, E element) {
454 Objects.checkIndex(index, size);
455 E oldValue = elementData(index);
456 elementData[index] = element;
457 return oldValue;
458 }
459
460 /**
461 * This helper method split out from add(E) to keep method
462 * bytecode size under 35 (the -XX:MaxInlineSize default value),
463 * which helps when add(E) is called in a C1-compiled loop.
464 */
465 private void add(E e, Object[] elementData, int s) {
466 if (s == elementData.length)
467 elementData = grow();
468 elementData[s] = e;
469 size = s + 1;
470 }
471
472 /**
473 * Appends the specified element to the end of this list.
474 *
475 * @param e element to be appended to this list
476 * @return {@code true} (as specified by {@link Collection#add})
477 */
478 public boolean add(E e) {
479 modCount++;
480 add(e, elementData, size);
481 return true;
482 }
483
484 /**
485 * Inserts the specified element at the specified position in this
486 * list. Shifts the element currently at that position (if any) and
487 * any subsequent elements to the right (adds one to their indices).
488 *
489 * @param index index at which the specified element is to be inserted
490 * @param element element to be inserted
491 * @throws IndexOutOfBoundsException {@inheritDoc}
492 */
493 public void add(int index, E element) {
494 rangeCheckForAdd(index);
495 modCount++;
496 final int s;
497 Object[] elementData;
498 if ((s = size) == (elementData = this.elementData).length)
499 elementData = grow();
500 System.arraycopy(elementData, index,
501 elementData, index + 1,
502 s - index);
503 elementData[index] = element;
504 size = s + 1;
505 }
506
507 /**
508 * Removes the element at the specified position in this list.
509 * Shifts any subsequent elements to the left (subtracts one from their
510 * indices).
511 *
512 * @param index the index of the element to be removed
513 * @return the element that was removed from the list
514 * @throws IndexOutOfBoundsException {@inheritDoc}
515 */
516 public E remove(int index) {
517 Objects.checkIndex(index, size);
518 final Object[] es = elementData;
519
520 @SuppressWarnings("unchecked") E oldValue = (E) es[index];
521 fastRemove(es, index);
522
523 return oldValue;
524 }
525
526 /**
527 * Removes the first occurrence of the specified element from this list,
528 * if it is present. If the list does not contain the element, it is
529 * unchanged. More formally, removes the element with the lowest index
530 * {@code i} such that
531 * {@code Objects.equals(o, get(i))}
532 * (if such an element exists). Returns {@code true} if this list
533 * contained the specified element (or equivalently, if this list
534 * changed as a result of the call).
535 *
536 * @param o element to be removed from this list, if present
537 * @return {@code true} if this list contained the specified element
538 */
539 public boolean remove(Object o) {
540 final Object[] es = elementData;
541 final int size = this.size;
542 int i = 0;
543 found: {
544 if (o == null) {
545 for (; i < size; i++)
546 if (es[i] == null)
547 break found;
548 } else {
549 for (; i < size; i++)
550 if (o.equals(es[i]))
551 break found;
552 }
553 return false;
554 }
555 fastRemove(es, i);
556 return true;
557 }
558
559 /**
560 * Private remove method that skips bounds checking and does not
561 * return the value removed.
562 */
563 private void fastRemove(Object[] es, int i) {
564 modCount++;
565 final int newSize;
566 if ((newSize = size - 1) > i)
567 System.arraycopy(es, i + 1, es, i, newSize - i);
568 es[size = newSize] = null;
569 }
570
571 /**
572 * Removes all of the elements from this list. The list will
573 * be empty after this call returns.
574 */
575 public void clear() {
576 modCount++;
577 final Object[] es = elementData;
578 for (int to = size, i = size = 0; i < to; i++)
579 es[i] = null;
580 }
581
582 /**
583 * Appends all of the elements in the specified collection to the end of
584 * this list, in the order that they are returned by the
585 * specified collection's Iterator. The behavior of this operation is
586 * undefined if the specified collection is modified while the operation
587 * is in progress. (This implies that the behavior of this call is
588 * undefined if the specified collection is this list, and this
589 * list is nonempty.)
590 *
591 * @param c collection containing elements to be added to this list
592 * @return {@code true} if this list changed as a result of the call
593 * @throws NullPointerException if the specified collection is null
594 */
595 public boolean addAll(Collection<? extends E> c) {
596 Object[] a = c.toArray();
597 modCount++;
598 int numNew = a.length;
599 if (numNew == 0)
600 return false;
601 Object[] elementData;
602 final int s;
603 if (numNew > (elementData = this.elementData).length - (s = size))
604 elementData = grow(s + numNew);
605 System.arraycopy(a, 0, elementData, s, numNew);
606 size = s + numNew;
607 return true;
608 }
609
610 /**
611 * Inserts all of the elements in the specified collection into this
612 * list, starting at the specified position. Shifts the element
613 * currently at that position (if any) and any subsequent elements to
614 * the right (increases their indices). The new elements will appear
615 * in the list in the order that they are returned by the
616 * specified collection's iterator.
617 *
618 * @param index index at which to insert the first element from the
619 * specified collection
620 * @param c collection containing elements to be added to this list
621 * @return {@code true} if this list changed as a result of the call
622 * @throws IndexOutOfBoundsException {@inheritDoc}
623 * @throws NullPointerException if the specified collection is null
624 */
625 public boolean addAll(int index, Collection<? extends E> c) {
626 rangeCheckForAdd(index);
627
628 Object[] a = c.toArray();
629 modCount++;
630 int numNew = a.length;
631 if (numNew == 0)
632 return false;
633 Object[] elementData;
634 final int s;
635 if (numNew > (elementData = this.elementData).length - (s = size))
636 elementData = grow(s + numNew);
637
638 int numMoved = s - index;
639 if (numMoved > 0)
640 System.arraycopy(elementData, index,
641 elementData, index + numNew,
642 numMoved);
643 System.arraycopy(a, 0, elementData, index, numNew);
644 size = s + numNew;
645 return true;
646 }
647
648 /**
649 * Removes from this list all of the elements whose index is between
650 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
651 * Shifts any succeeding elements to the left (reduces their index).
652 * This call shortens the list by {@code (toIndex - fromIndex)} elements.
653 * (If {@code toIndex==fromIndex}, this operation has no effect.)
654 *
655 * @throws IndexOutOfBoundsException if {@code fromIndex} or
656 * {@code toIndex} is out of range
657 * ({@code fromIndex < 0 ||
658 * toIndex > size() ||
659 * toIndex < fromIndex})
660 */
661 protected void removeRange(int fromIndex, int toIndex) {
662 if (fromIndex > toIndex) {
663 throw new IndexOutOfBoundsException(
664 outOfBoundsMsg(fromIndex, toIndex));
665 }
666 modCount++;
667 shiftTailOverGap(elementData, fromIndex, toIndex);
668 }
669
670 /** Erases the gap from lo to hi, by sliding down following elements. */
671 private void shiftTailOverGap(Object[] es, int lo, int hi) {
672 System.arraycopy(es, hi, es, lo, size - hi);
673 for (int to = size, i = (size -= hi - lo); i < to; i++)
674 es[i] = null;
675 }
676
677 /**
678 * A version of rangeCheck used by add and addAll.
679 */
680 private void rangeCheckForAdd(int index) {
681 if (index > size || index < 0)
682 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
683 }
684
685 /**
686 * Constructs an IndexOutOfBoundsException detail message.
687 * Of the many possible refactorings of the error handling code,
688 * this "outlining" performs best with both server and client VMs.
689 */
690 private String outOfBoundsMsg(int index) {
691 return "Index: "+index+", Size: "+size;
692 }
693
694 /**
695 * A version used in checking (fromIndex > toIndex) condition
696 */
697 private static String outOfBoundsMsg(int fromIndex, int toIndex) {
698 return "From Index: " + fromIndex + " > To Index: " + toIndex;
699 }
700
701 /**
702 * Removes from this list all of its elements that are contained in the
703 * specified collection.
704 *
705 * @param c collection containing elements to be removed from this list
706 * @return {@code true} if this list changed as a result of the call
707 * @throws ClassCastException if the class of an element of this list
708 * is incompatible with the specified collection
709 * (<a href="Collection.html#optional-restrictions">optional</a>)
710 * @throws NullPointerException if this list contains a null element and the
711 * specified collection does not permit null elements
712 * (<a href="Collection.html#optional-restrictions">optional</a>),
713 * or if the specified collection is null
714 * @see Collection#contains(Object)
715 */
716 public boolean removeAll(Collection<?> c) {
717 return batchRemove(c, false, 0, size);
718 }
719
720 /**
721 * Retains only the elements in this list that are contained in the
722 * specified collection. In other words, removes from this list all
723 * of its elements that are not contained in the specified collection.
724 *
725 * @param c collection containing elements to be retained in this list
726 * @return {@code true} if this list changed as a result of the call
727 * @throws ClassCastException if the class of an element of this list
728 * is incompatible with the specified collection
729 * (<a href="Collection.html#optional-restrictions">optional</a>)
730 * @throws NullPointerException if this list contains a null element and the
731 * specified collection does not permit null elements
732 * (<a href="Collection.html#optional-restrictions">optional</a>),
733 * or if the specified collection is null
734 * @see Collection#contains(Object)
735 */
736 public boolean retainAll(Collection<?> c) {
737 return batchRemove(c, true, 0, size);
738 }
739
740 boolean batchRemove(Collection<?> c, boolean complement,
741 final int from, final int end) {
742 Objects.requireNonNull(c);
743 final Object[] es = elementData;
744 int r;
745 // Optimize for initial run of survivors
746 for (r = from;; r++) {
747 if (r == end)
748 return false;
749 if (c.contains(es[r]) != complement)
750 break;
751 }
752 int w = r++;
753 try {
754 for (Object e; r < end; r++)
755 if (c.contains(e = es[r]) == complement)
756 es[w++] = e;
757 } catch (Throwable ex) {
758 // Preserve behavioral compatibility with AbstractCollection,
759 // even if c.contains() throws.
760 System.arraycopy(es, r, es, w, end - r);
761 w += end - r;
762 throw ex;
763 } finally {
764 modCount += end - w;
765 shiftTailOverGap(es, w, end);
766 }
767 return true;
768 }
769
770 /**
771 * Saves the state of the {@code ArrayList} instance to a stream
772 * (that is, serializes it).
773 *
774 * @param s the stream
775 * @throws java.io.IOException if an I/O error occurs
776 * @serialData The length of the array backing the {@code ArrayList}
777 * instance is emitted (int), followed by all of its elements
778 * (each an {@code Object}) in the proper order.
779 */
780 private void writeObject(java.io.ObjectOutputStream s)
781 throws java.io.IOException {
782 // Write out element count, and any hidden stuff
783 int expectedModCount = modCount;
784 s.defaultWriteObject();
785
786 // Write out size as capacity for behavioral compatibility with clone()
787 s.writeInt(size);
788
789 // Write out all elements in the proper order.
790 for (int i=0; i<size; i++) {
791 s.writeObject(elementData[i]);
792 }
793
794 if (modCount != expectedModCount) {
795 throw new ConcurrentModificationException();
796 }
797 }
798
799 /**
800 * Reconstitutes the {@code ArrayList} instance from a stream (that is,
801 * deserializes it).
802 * @param s the stream
803 * @throws ClassNotFoundException if the class of a serialized object
804 * could not be found
805 * @throws java.io.IOException if an I/O error occurs
806 */
807 private void readObject(java.io.ObjectInputStream s)
808 throws java.io.IOException, ClassNotFoundException {
809
810 // Read in size, and any hidden stuff
811 s.defaultReadObject();
812
813 // Read in capacity
814 s.readInt(); // ignored
815
816 if (size > 0) {
817 // like clone(), allocate array based upon size not capacity
818 SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, size);
819 Object[] elements = new Object[size];
820
821 // Read in all elements in the proper order.
822 for (int i = 0; i < size; i++) {
823 elements[i] = s.readObject();
824 }
825
826 elementData = elements;
827 } else if (size == 0) {
828 elementData = EMPTY_ELEMENTDATA;
829 } else {
830 throw new java.io.InvalidObjectException("Invalid size: " + size);
831 }
832 }
833
834 /**
835 * Returns a list iterator over the elements in this list (in proper
836 * sequence), starting at the specified position in the list.
837 * The specified index indicates the first element that would be
838 * returned by an initial call to {@link ListIterator#next next}.
839 * An initial call to {@link ListIterator#previous previous} would
840 * return the element with the specified index minus one.
841 *
842 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
843 *
844 * @throws IndexOutOfBoundsException {@inheritDoc}
845 */
846 public ListIterator<E> listIterator(int index) {
847 rangeCheckForAdd(index);
848 return new ListItr(index);
849 }
850
851 /**
852 * Returns a list iterator over the elements in this list (in proper
853 * sequence).
854 *
855 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
856 *
857 * @see #listIterator(int)
858 */
859 public ListIterator<E> listIterator() {
860 return new ListItr(0);
861 }
862
863 /**
864 * Returns an iterator over the elements in this list in proper sequence.
865 *
866 * <p>The returned iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
867 *
868 * @return an iterator over the elements in this list in proper sequence
869 */
870 public Iterator<E> iterator() {
871 return new Itr();
872 }
873
874 /**
875 * An optimized version of AbstractList.Itr
876 */
877 private class Itr implements Iterator<E> {
878 int cursor; // index of next element to return
879 int lastRet = -1; // index of last element returned; -1 if no such
880 int expectedModCount = modCount;
881
882 // prevent creating a synthetic constructor
883 Itr() {}
884
885 public boolean hasNext() {
886 return cursor != size;
887 }
888
889 @SuppressWarnings("unchecked")
890 public E next() {
891 checkForComodification();
892 int i = cursor;
893 if (i >= size)
894 throw new NoSuchElementException();
895 Object[] elementData = ArrayList.this.elementData;
896 if (i >= elementData.length)
897 throw new ConcurrentModificationException();
898 cursor = i + 1;
899 return (E) elementData[lastRet = i];
900 }
901
902 public void remove() {
903 if (lastRet < 0)
904 throw new IllegalStateException();
905 checkForComodification();
906
907 try {
908 ArrayList.this.remove(lastRet);
909 cursor = lastRet;
910 lastRet = -1;
911 expectedModCount = modCount;
912 } catch (IndexOutOfBoundsException ex) {
913 throw new ConcurrentModificationException();
914 }
915 }
916
917 @Override
918 public void forEachRemaining(Consumer<? super E> action) {
919 Objects.requireNonNull(action);
920 final int size = ArrayList.this.size;
921 int i = cursor;
922 if (i < size) {
923 final Object[] es = elementData;
924 if (i >= es.length)
925 throw new ConcurrentModificationException();
926 for (; i < size && modCount == expectedModCount; i++)
927 action.accept(elementAt(es, i));
928 // update once at end to reduce heap write traffic
929 cursor = i;
930 lastRet = i - 1;
931 checkForComodification();
932 }
933 }
934
935 final void checkForComodification() {
936 if (modCount != expectedModCount)
937 throw new ConcurrentModificationException();
938 }
939 }
940
941 /**
942 * An optimized version of AbstractList.ListItr
943 */
944 private class ListItr extends Itr implements ListIterator<E> {
945 ListItr(int index) {
946 super();
947 cursor = index;
948 }
949
950 public boolean hasPrevious() {
951 return cursor != 0;
952 }
953
954 public int nextIndex() {
955 return cursor;
956 }
957
958 public int previousIndex() {
959 return cursor - 1;
960 }
961
962 @SuppressWarnings("unchecked")
963 public E previous() {
964 checkForComodification();
965 int i = cursor - 1;
966 if (i < 0)
967 throw new NoSuchElementException();
968 Object[] elementData = ArrayList.this.elementData;
969 if (i >= elementData.length)
970 throw new ConcurrentModificationException();
971 cursor = i;
972 return (E) elementData[lastRet = i];
973 }
974
975 public void set(E e) {
976 if (lastRet < 0)
977 throw new IllegalStateException();
978 checkForComodification();
979
980 try {
981 ArrayList.this.set(lastRet, e);
982 } catch (IndexOutOfBoundsException ex) {
983 throw new ConcurrentModificationException();
984 }
985 }
986
987 public void add(E e) {
988 checkForComodification();
989
990 try {
991 int i = cursor;
992 ArrayList.this.add(i, e);
993 cursor = i + 1;
994 lastRet = -1;
995 expectedModCount = modCount;
996 } catch (IndexOutOfBoundsException ex) {
997 throw new ConcurrentModificationException();
998 }
999 }
1000 }
1001
1002 /**
1003 * Returns a view of the portion of this list between the specified
1004 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. (If
1005 * {@code fromIndex} and {@code toIndex} are equal, the returned list is
1006 * empty.) The returned list is backed by this list, so non-structural
1007 * changes in the returned list are reflected in this list, and vice-versa.
1008 * The returned list supports all of the optional list operations.
1009 *
1010 * <p>This method eliminates the need for explicit range operations (of
1011 * the sort that commonly exist for arrays). Any operation that expects
1012 * a list can be used as a range operation by passing a subList view
1013 * instead of a whole list. For example, the following idiom
1014 * removes a range of elements from a list:
1015 * <pre>
1016 * list.subList(from, to).clear();
1017 * </pre>
1018 * Similar idioms may be constructed for {@link #indexOf(Object)} and
1019 * {@link #lastIndexOf(Object)}, and all of the algorithms in the
1020 * {@link Collections} class can be applied to a subList.
1021 *
1022 * <p>The semantics of the list returned by this method become undefined if
1023 * the backing list (i.e., this list) is <i>structurally modified</i> in
1024 * any way other than via the returned list. (Structural modifications are
1025 * those that change the size of this list, or otherwise perturb it in such
1026 * a fashion that iterations in progress may yield incorrect results.)
1027 *
1028 * @throws IndexOutOfBoundsException {@inheritDoc}
1029 * @throws IllegalArgumentException {@inheritDoc}
1030 */
1031 public List<E> subList(int fromIndex, int toIndex) {
1032 subListRangeCheck(fromIndex, toIndex, size);
1033 return new SubList<>(this, fromIndex, toIndex);
1034 }
1035
1036 private static class SubList<E> extends AbstractList<E> implements RandomAccess {
1037 private final ArrayList<E> root;
1038 private final SubList<E> parent;
1039 private final int offset;
1040 private int size;
1041
1042 /**
1043 * Constructs a sublist of an arbitrary ArrayList.
1044 */
1045 public SubList(ArrayList<E> root, int fromIndex, int toIndex) {
1046 this.root = root;
1047 this.parent = null;
1048 this.offset = fromIndex;
1049 this.size = toIndex - fromIndex;
1050 this.modCount = root.modCount;
1051 }
1052
1053 /**
1054 * Constructs a sublist of another SubList.
1055 */
1056 private SubList(SubList<E> parent, int fromIndex, int toIndex) {
1057 this.root = parent.root;
1058 this.parent = parent;
1059 this.offset = parent.offset + fromIndex;
1060 this.size = toIndex - fromIndex;
1061 this.modCount = root.modCount;
1062 }
1063
1064 public E set(int index, E element) {
1065 Objects.checkIndex(index, size);
1066 checkForComodification();
1067 E oldValue = root.elementData(offset + index);
1068 root.elementData[offset + index] = element;
1069 return oldValue;
1070 }
1071
1072 public E get(int index) {
1073 Objects.checkIndex(index, size);
1074 checkForComodification();
1075 return root.elementData(offset + index);
1076 }
1077
1078 public int size() {
1079 checkForComodification();
1080 return size;
1081 }
1082
1083 public void add(int index, E element) {
1084 rangeCheckForAdd(index);
1085 checkForComodification();
1086 root.add(offset + index, element);
1087 updateSizeAndModCount(1);
1088 }
1089
1090 public E remove(int index) {
1091 Objects.checkIndex(index, size);
1092 checkForComodification();
1093 E result = root.remove(offset + index);
1094 updateSizeAndModCount(-1);
1095 return result;
1096 }
1097
1098 protected void removeRange(int fromIndex, int toIndex) {
1099 checkForComodification();
1100 root.removeRange(offset + fromIndex, offset + toIndex);
1101 updateSizeAndModCount(fromIndex - toIndex);
1102 }
1103
1104 public boolean addAll(Collection<? extends E> c) {
1105 return addAll(this.size, c);
1106 }
1107
1108 public boolean addAll(int index, Collection<? extends E> c) {
1109 rangeCheckForAdd(index);
1110 int cSize = c.size();
1111 if (cSize==0)
1112 return false;
1113 checkForComodification();
1114 root.addAll(offset + index, c);
1115 updateSizeAndModCount(cSize);
1116 return true;
1117 }
1118
1119 public boolean removeAll(Collection<?> c) {
1120 return batchRemove(c, false);
1121 }
1122
1123 public boolean retainAll(Collection<?> c) {
1124 return batchRemove(c, true);
1125 }
1126
1127 private boolean batchRemove(Collection<?> c, boolean complement) {
1128 checkForComodification();
1129 int oldSize = root.size;
1130 boolean modified =
1131 root.batchRemove(c, complement, offset, offset + size);
1132 if (modified)
1133 updateSizeAndModCount(root.size - oldSize);
1134 return modified;
1135 }
1136
1137 public boolean removeIf(Predicate<? super E> filter) {
1138 checkForComodification();
1139 int oldSize = root.size;
1140 boolean modified = root.removeIf(filter, offset, offset + size);
1141 if (modified)
1142 updateSizeAndModCount(root.size - oldSize);
1143 return modified;
1144 }
1145
1146 public Iterator<E> iterator() {
1147 return listIterator();
1148 }
1149
1150 public ListIterator<E> listIterator(int index) {
1151 checkForComodification();
1152 rangeCheckForAdd(index);
1153
1154 return new ListIterator<E>() {
1155 int cursor = index;
1156 int lastRet = -1;
1157 int expectedModCount = root.modCount;
1158
1159 public boolean hasNext() {
1160 return cursor != SubList.this.size;
1161 }
1162
1163 @SuppressWarnings("unchecked")
1164 public E next() {
1165 checkForComodification();
1166 int i = cursor;
1167 if (i >= SubList.this.size)
1168 throw new NoSuchElementException();
1169 Object[] elementData = root.elementData;
1170 if (offset + i >= elementData.length)
1171 throw new ConcurrentModificationException();
1172 cursor = i + 1;
1173 return (E) elementData[offset + (lastRet = i)];
1174 }
1175
1176 public boolean hasPrevious() {
1177 return cursor != 0;
1178 }
1179
1180 @SuppressWarnings("unchecked")
1181 public E previous() {
1182 checkForComodification();
1183 int i = cursor - 1;
1184 if (i < 0)
1185 throw new NoSuchElementException();
1186 Object[] elementData = root.elementData;
1187 if (offset + i >= elementData.length)
1188 throw new ConcurrentModificationException();
1189 cursor = i;
1190 return (E) elementData[offset + (lastRet = i)];
1191 }
1192
1193 public void forEachRemaining(Consumer<? super E> action) {
1194 Objects.requireNonNull(action);
1195 final int size = SubList.this.size;
1196 int i = cursor;
1197 if (i < size) {
1198 final Object[] es = root.elementData;
1199 if (offset + i >= es.length)
1200 throw new ConcurrentModificationException();
1201 for (; i < size && modCount == expectedModCount; i++)
1202 action.accept(elementAt(es, offset + i));
1203 // update once at end to reduce heap write traffic
1204 cursor = i;
1205 lastRet = i - 1;
1206 checkForComodification();
1207 }
1208 }
1209
1210 public int nextIndex() {
1211 return cursor;
1212 }
1213
1214 public int previousIndex() {
1215 return cursor - 1;
1216 }
1217
1218 public void remove() {
1219 if (lastRet < 0)
1220 throw new IllegalStateException();
1221 checkForComodification();
1222
1223 try {
1224 SubList.this.remove(lastRet);
1225 cursor = lastRet;
1226 lastRet = -1;
1227 expectedModCount = root.modCount;
1228 } catch (IndexOutOfBoundsException ex) {
1229 throw new ConcurrentModificationException();
1230 }
1231 }
1232
1233 public void set(E e) {
1234 if (lastRet < 0)
1235 throw new IllegalStateException();
1236 checkForComodification();
1237
1238 try {
1239 root.set(offset + lastRet, e);
1240 } catch (IndexOutOfBoundsException ex) {
1241 throw new ConcurrentModificationException();
1242 }
1243 }
1244
1245 public void add(E e) {
1246 checkForComodification();
1247
1248 try {
1249 int i = cursor;
1250 SubList.this.add(i, e);
1251 cursor = i + 1;
1252 lastRet = -1;
1253 expectedModCount = root.modCount;
1254 } catch (IndexOutOfBoundsException ex) {
1255 throw new ConcurrentModificationException();
1256 }
1257 }
1258
1259 final void checkForComodification() {
1260 if (root.modCount != expectedModCount)
1261 throw new ConcurrentModificationException();
1262 }
1263 };
1264 }
1265
1266 public List<E> subList(int fromIndex, int toIndex) {
1267 subListRangeCheck(fromIndex, toIndex, size);
1268 return new SubList<>(this, fromIndex, toIndex);
1269 }
1270
1271 private void rangeCheckForAdd(int index) {
1272 if (index < 0 || index > this.size)
1273 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
1274 }
1275
1276 private String outOfBoundsMsg(int index) {
1277 return "Index: "+index+", Size: "+this.size;
1278 }
1279
1280 private void checkForComodification() {
1281 if (root.modCount != modCount)
1282 throw new ConcurrentModificationException();
1283 }
1284
1285 private void updateSizeAndModCount(int sizeChange) {
1286 SubList<E> slist = this;
1287 do {
1288 slist.size += sizeChange;
1289 slist.modCount = root.modCount;
1290 slist = slist.parent;
1291 } while (slist != null);
1292 }
1293
1294 public Spliterator<E> spliterator() {
1295 checkForComodification();
1296
1297 // ArrayListSpliterator not used here due to late-binding
1298 return new Spliterator<E>() {
1299 private int index = offset; // current index, modified on advance/split
1300 private int fence = -1; // -1 until used; then one past last index
1301 private int expectedModCount; // initialized when fence set
1302
1303 private int getFence() { // initialize fence to size on first use
1304 int hi; // (a specialized variant appears in method forEach)
1305 if ((hi = fence) < 0) {
1306 expectedModCount = modCount;
1307 hi = fence = offset + size;
1308 }
1309 return hi;
1310 }
1311
1312 public ArrayList<E>.ArrayListSpliterator trySplit() {
1313 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1314 // ArrayListSpliterator can be used here as the source is already bound
1315 return (lo >= mid) ? null : // divide range in half unless too small
1316 root.new ArrayListSpliterator(lo, index = mid, expectedModCount);
1317 }
1318
1319 public boolean tryAdvance(Consumer<? super E> action) {
1320 Objects.requireNonNull(action);
1321 int hi = getFence(), i = index;
1322 if (i < hi) {
1323 index = i + 1;
1324 @SuppressWarnings("unchecked") E e = (E)root.elementData[i];
1325 action.accept(e);
1326 if (root.modCount != expectedModCount)
1327 throw new ConcurrentModificationException();
1328 return true;
1329 }
1330 return false;
1331 }
1332
1333 public void forEachRemaining(Consumer<? super E> action) {
1334 Objects.requireNonNull(action);
1335 int i, hi, mc; // hoist accesses and checks from loop
1336 ArrayList<E> lst = root;
1337 Object[] a;
1338 if ((a = lst.elementData) != null) {
1339 if ((hi = fence) < 0) {
1340 mc = modCount;
1341 hi = offset + size;
1342 }
1343 else
1344 mc = expectedModCount;
1345 if ((i = index) >= 0 && (index = hi) <= a.length) {
1346 for (; i < hi; ++i) {
1347 @SuppressWarnings("unchecked") E e = (E) a[i];
1348 action.accept(e);
1349 }
1350 if (lst.modCount == mc)
1351 return;
1352 }
1353 }
1354 throw new ConcurrentModificationException();
1355 }
1356
1357 public long estimateSize() {
1358 return getFence() - index;
1359 }
1360
1361 public int characteristics() {
1362 return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
1363 }
1364 };
1365 }
1366 }
1367
1368 /**
1369 * @throws NullPointerException {@inheritDoc}
1370 */
1371 @Override
1372 public void forEach(Consumer<? super E> action) {
1373 Objects.requireNonNull(action);
1374 final int expectedModCount = modCount;
1375 final Object[] es = elementData;
1376 final int size = this.size;
1377 for (int i = 0; modCount == expectedModCount && i < size; i++)
1378 action.accept(elementAt(es, i));
1379 if (modCount != expectedModCount)
1380 throw new ConcurrentModificationException();
1381 }
1382
1383 /**
1384 * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
1385 * and <em>fail-fast</em> {@link Spliterator} over the elements in this
1386 * list.
1387 *
1388 * <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
1389 * {@link Spliterator#SUBSIZED}, and {@link Spliterator#ORDERED}.
1390 * Overriding implementations should document the reporting of additional
1391 * characteristic values.
1392 *
1393 * @return a {@code Spliterator} over the elements in this list
1394 * @since 1.8
1395 */
1396 @Override
1397 public Spliterator<E> spliterator() {
1398 return new ArrayListSpliterator(0, -1, 0);
1399 }
1400
1401 /** Index-based split-by-two, lazily initialized Spliterator */
1402 final class ArrayListSpliterator implements Spliterator<E> {
1403
1404 /*
1405 * If ArrayLists were immutable, or structurally immutable (no
1406 * adds, removes, etc), we could implement their spliterators
1407 * with Arrays.spliterator. Instead we detect as much
1408 * interference during traversal as practical without
1409 * sacrificing much performance. We rely primarily on
1410 * modCounts. These are not guaranteed to detect concurrency
1411 * violations, and are sometimes overly conservative about
1412 * within-thread interference, but detect enough problems to
1413 * be worthwhile in practice. To carry this out, we (1) lazily
1414 * initialize fence and expectedModCount until the latest
1415 * point that we need to commit to the state we are checking
1416 * against; thus improving precision. (This doesn't apply to
1417 * SubLists, that create spliterators with current non-lazy
1418 * values). (2) We perform only a single
1419 * ConcurrentModificationException check at the end of forEach
1420 * (the most performance-sensitive method). When using forEach
1421 * (as opposed to iterators), we can normally only detect
1422 * interference after actions, not before. Further
1423 * CME-triggering checks apply to all other possible
1424 * violations of assumptions for example null or too-small
1425 * elementData array given its size(), that could only have
1426 * occurred due to interference. This allows the inner loop
1427 * of forEach to run without any further checks, and
1428 * simplifies lambda-resolution. While this does entail a
1429 * number of checks, note that in the common case of
1430 * list.stream().forEach(a), no checks or other computation
1431 * occur anywhere other than inside forEach itself. The other
1432 * less-often-used methods cannot take advantage of most of
1433 * these streamlinings.
1434 */
1435
1436 private int index; // current index, modified on advance/split
1437 private int fence; // -1 until used; then one past last index
1438 private int expectedModCount; // initialized when fence set
1439
1440 /** Creates new spliterator covering the given range. */
1441 ArrayListSpliterator(int origin, int fence, int expectedModCount) {
1442 this.index = origin;
1443 this.fence = fence;
1444 this.expectedModCount = expectedModCount;
1445 }
1446
1447 private int getFence() { // initialize fence to size on first use
1448 int hi; // (a specialized variant appears in method forEach)
1449 if ((hi = fence) < 0) {
1450 expectedModCount = modCount;
1451 hi = fence = size;
1452 }
1453 return hi;
1454 }
1455
1456 public ArrayListSpliterator trySplit() {
1457 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1458 return (lo >= mid) ? null : // divide range in half unless too small
1459 new ArrayListSpliterator(lo, index = mid, expectedModCount);
1460 }
1461
1462 public boolean tryAdvance(Consumer<? super E> action) {
1463 if (action == null)
1464 throw new NullPointerException();
1465 int hi = getFence(), i = index;
1466 if (i < hi) {
1467 index = i + 1;
1468 @SuppressWarnings("unchecked") E e = (E)elementData[i];
1469 action.accept(e);
1470 if (modCount != expectedModCount)
1471 throw new ConcurrentModificationException();
1472 return true;
1473 }
1474 return false;
1475 }
1476
1477 public void forEachRemaining(Consumer<? super E> action) {
1478 int i, hi, mc; // hoist accesses and checks from loop
1479 Object[] a;
1480 if (action == null)
1481 throw new NullPointerException();
1482 if ((a = elementData) != null) {
1483 if ((hi = fence) < 0) {
1484 mc = modCount;
1485 hi = size;
1486 }
1487 else
1488 mc = expectedModCount;
1489 if ((i = index) >= 0 && (index = hi) <= a.length) {
1490 for (; i < hi; ++i) {
1491 @SuppressWarnings("unchecked") E e = (E) a[i];
1492 action.accept(e);
1493 }
1494 if (modCount == mc)
1495 return;
1496 }
1497 }
1498 throw new ConcurrentModificationException();
1499 }
1500
1501 public long estimateSize() {
1502 return getFence() - index;
1503 }
1504
1505 public int characteristics() {
1506 return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
1507 }
1508 }
1509
1510 // A tiny bit set implementation
1511
1512 private static long[] nBits(int n) {
1513 return new long[((n - 1) >> 6) + 1];
1514 }
1515 private static void setBit(long[] bits, int i) {
1516 bits[i >> 6] |= 1L << i;
1517 }
1518 private static boolean isClear(long[] bits, int i) {
1519 return (bits[i >> 6] & (1L << i)) == 0;
1520 }
1521
1522 /**
1523 * @throws NullPointerException {@inheritDoc}
1524 */
1525 @Override
1526 public boolean removeIf(Predicate<? super E> filter) {
1527 return removeIf(filter, 0, size);
1528 }
1529
1530 /**
1531 * Removes all elements satisfying the given predicate, from index
1532 * i (inclusive) to index end (exclusive).
1533 */
1534 boolean removeIf(Predicate<? super E> filter, int i, final int end) {
1535 Objects.requireNonNull(filter);
1536 int expectedModCount = modCount;
1537 final Object[] es = elementData;
1538 // Optimize for initial run of survivors
1539 for (; i < end && !filter.test(elementAt(es, i)); i++)
1540 ;
1541 // Tolerate predicates that reentrantly access the collection for
1542 // read (but writers still get CME), so traverse once to find
1543 // elements to delete, a second pass to physically expunge.
1544 if (i < end) {
1545 final int beg = i;
1546 final long[] deathRow = nBits(end - beg);
1547 deathRow[0] = 1L; // set bit 0
1548 for (i = beg + 1; i < end; i++)
1549 if (filter.test(elementAt(es, i)))
1550 setBit(deathRow, i - beg);
1551 if (modCount != expectedModCount)
1552 throw new ConcurrentModificationException();
1553 expectedModCount++;
1554 modCount++;
1555 int w = beg;
1556 for (i = beg; i < end; i++)
1557 if (isClear(deathRow, i - beg))
1558 es[w++] = es[i];
1559 shiftTailOverGap(es, w, end);
1560 return true;
1561 } else {
1562 if (modCount != expectedModCount)
1563 throw new ConcurrentModificationException();
1564 return false;
1565 }
1566 }
1567
1568 @Override
1569 public void replaceAll(UnaryOperator<E> operator) {
1570 Objects.requireNonNull(operator);
1571 final int expectedModCount = modCount;
1572 final Object[] es = elementData;
1573 final int size = this.size;
1574 for (int i = 0; modCount == expectedModCount && i < size; i++)
1575 es[i] = operator.apply(elementAt(es, i));
1576 if (modCount != expectedModCount)
1577 throw new ConcurrentModificationException();
1578 modCount++;
1579 }
1580
1581 @Override
1582 @SuppressWarnings("unchecked")
1583 public void sort(Comparator<? super E> c) {
1584 final int expectedModCount = modCount;
1585 Arrays.sort((E[]) elementData, 0, size, c);
1586 if (modCount != expectedModCount)
1587 throw new ConcurrentModificationException();
1588 modCount++;
1589 }
1590
1591 void checkInvariants() {
1592 // assert size >= 0;
1593 // assert size == elementData.length || elementData[size] == null;
1594 }
1595 }