1 /*
2 * Copyright (c) 1997, 2013, 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
32 /**
33 * Resizable-array implementation of the <tt>List</tt> interface. Implements
34 * all optional list operations, and permits all elements, including
35 * <tt>null</tt>. In addition to implementing the <tt>List</tt> interface,
36 * this class provides methods to manipulate the size of the array that is
37 * used internally to store the list. (This class is roughly equivalent to
38 * <tt>Vector</tt>, except that it is unsynchronized.)
39 *
40 * <p>The <tt>size</tt>, <tt>isEmpty</tt>, <tt>get</tt>, <tt>set</tt>,
41 * <tt>iterator</tt>, and <tt>listIterator</tt> operations run in constant
42 * time. The <tt>add</tt> operation runs in <i>amortized constant time</i>,
43 * that is, adding n elements requires O(n) time. All of the other operations
44 * run in linear time (roughly speaking). The constant factor is low compared
45 * to that for the <tt>LinkedList</tt> implementation.
46 *
47 * <p>Each <tt>ArrayList</tt> instance has a <i>capacity</i>. The capacity is
48 * the size of the array used to store the elements in the list. It is always
49 * at least as large as the list size. As elements are added to an ArrayList,
50 * its capacity grows automatically. The details of the growth policy are not
51 * specified beyond the fact that adding an element has constant amortized
52 * time cost.
53 *
54 * <p>An application can increase the capacity of an <tt>ArrayList</tt> instance
55 * before adding a large number of elements using the <tt>ensureCapacity</tt>
56 * operation. This may reduce the amount of incremental reallocation.
57 *
58 * <p><strong>Note that this implementation is not synchronized.</strong>
59 * If multiple threads access an <tt>ArrayList</tt> instance concurrently,
60 * and at least one of the threads modifies the list structurally, it
61 * <i>must</i> be synchronized externally. (A structural modification is
62 * any operation that adds or deletes one or more elements, or explicitly
63 * resizes the backing array; merely setting the value of an element is not
64 * a structural modification.) This is typically accomplished by
65 * synchronizing on some object that naturally encapsulates the list.
66 *
67 * If no such object exists, the list should be "wrapped" using the
68 * {@link Collections#synchronizedList Collections.synchronizedList}
69 * method. This is best done at creation time, to prevent accidental
70 * unsynchronized access to the list:<pre>
71 * List list = Collections.synchronizedList(new ArrayList(...));</pre>
72 *
73 * <p><a name="fail-fast">
74 * The iterators returned by this class's {@link #iterator() iterator} and
75 * {@link #listIterator(int) listIterator} methods are <em>fail-fast</em>:</a>
76 * if the list is structurally modified at any time after the iterator is
77 * created, in any way except through the iterator's own
78 * {@link ListIterator#remove() remove} or
79 * {@link ListIterator#add(Object) add} methods, the iterator will throw a
80 * {@link ConcurrentModificationException}. Thus, in the face of
81 * concurrent modification, the iterator fails quickly and cleanly, rather
82 * than risking arbitrary, non-deterministic behavior at an undetermined
83 * time in the future.
84 *
85 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
86 * as it is, generally speaking, impossible to make any hard guarantees in the
87 * presence of unsynchronized concurrent modification. Fail-fast iterators
88 * throw {@code ConcurrentModificationException} on a best-effort basis.
89 * Therefore, it would be wrong to write a program that depended on this
90 * exception for its correctness: <i>the fail-fast behavior of iterators
91 * should be used only to detect bugs.</i>
92 *
93 * <p>This class is a member of the
94 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
95 * Java Collections Framework</a>.
96 *
97 * @author Josh Bloch
98 * @author Neal Gafter
99 * @see Collection
100 * @see List
101 * @see LinkedList
102 * @see Vector
103 * @since 1.2
104 */
105
106 public class ArrayList<E> extends AbstractList<E>
107 implements List<E>, RandomAccess, Cloneable, java.io.Serializable
108 {
109 private static final long serialVersionUID = 8683452581122892189L;
110
111 /**
112 * Default initial capacity.
113 */
114 private static final int DEFAULT_CAPACITY = 10;
115
116 /**
117 * Shared empty array instance used for empty instances.
118 */
119 private static final Object[] EMPTY_ELEMENTDATA = {};
120
121 /**
122 * The array buffer into which the elements of the ArrayList are stored.
123 * The capacity of the ArrayList is the length of this array buffer. Any
124 * empty ArrayList with elementData == EMPTY_ELEMENTDATA will be expanded to
125 * DEFAULT_CAPACITY when the first element is added.
126 */
127 transient Object[] elementData; // non-private to simplify nested class access
128
129 /**
130 * The size of the ArrayList (the number of elements it contains).
131 *
132 * @serial
133 */
134 private int size;
135
136 /**
137 * Constructs an empty list with the specified initial capacity.
138 *
139 * @param initialCapacity the initial capacity of the list
140 * @throws IllegalArgumentException if the specified initial capacity
141 * is negative
142 */
143 public ArrayList(int initialCapacity) {
144 super();
145 if (initialCapacity < 0)
146 throw new IllegalArgumentException("Illegal Capacity: "+
147 initialCapacity);
148 this.elementData = new Object[initialCapacity];
149 }
150
151 /**
152 * Constructs an empty list with an initial capacity of ten.
153 */
154 public ArrayList() {
155 super();
156 this.elementData = EMPTY_ELEMENTDATA;
157 }
158
159 /**
160 * Constructs a list containing the elements of the specified
161 * collection, in the order they are returned by the collection's
162 * iterator.
163 *
164 * @param c the collection whose elements are to be placed into this list
165 * @throws NullPointerException if the specified collection is null
166 */
167 public ArrayList(Collection<? extends E> c) {
168 elementData = c.toArray();
169 size = elementData.length;
170 // c.toArray might (incorrectly) not return Object[] (see 6260652)
171 if (elementData.getClass() != Object[].class)
172 elementData = Arrays.copyOf(elementData, size, Object[].class);
173 }
174
175 /**
176 * Trims the capacity of this <tt>ArrayList</tt> instance to be the
177 * list's current size. An application can use this operation to minimize
178 * the storage of an <tt>ArrayList</tt> instance.
179 */
180 public void trimToSize() {
181 modCount++;
182 if (size < elementData.length) {
183 elementData = Arrays.copyOf(elementData, size);
184 }
185 }
186
187 /**
188 * Increases the capacity of this <tt>ArrayList</tt> instance, if
189 * necessary, to ensure that it can hold at least the number of elements
190 * specified by the minimum capacity argument.
191 *
192 * @param minCapacity the desired minimum capacity
193 */
194 public void ensureCapacity(int minCapacity) {
195 int minExpand = (elementData != EMPTY_ELEMENTDATA)
196 // any size if real element table
197 ? 0
198 // larger than default for empty table. It's already supposed to be
199 // at default size.
200 : DEFAULT_CAPACITY;
201
202 if (minCapacity > minExpand) {
203 ensureExplicitCapacity(minCapacity);
204 }
205 }
206
207 private void ensureCapacityInternal(int minCapacity) {
208 if (elementData == EMPTY_ELEMENTDATA) {
209 minCapacity = Math.max(DEFAULT_CAPACITY, minCapacity);
210 }
211
212 ensureExplicitCapacity(minCapacity);
213 }
214
215 private void ensureExplicitCapacity(int minCapacity) {
216 modCount++;
217
218 // overflow-conscious code
219 if (minCapacity - elementData.length > 0)
220 grow(minCapacity);
221 }
222
223 /**
224 * The maximum size of array to allocate.
225 * Some VMs reserve some header words in an array.
226 * Attempts to allocate larger arrays may result in
227 * OutOfMemoryError: Requested array size exceeds VM limit
228 */
229 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
230
231 /**
232 * Increases the capacity to ensure that it can hold at least the
233 * number of elements specified by the minimum capacity argument.
234 *
235 * @param minCapacity the desired minimum capacity
236 */
237 private void grow(int minCapacity) {
238 // overflow-conscious code
239 int oldCapacity = elementData.length;
240 int newCapacity = oldCapacity + (oldCapacity >> 1);
241 if (newCapacity - minCapacity < 0)
242 newCapacity = minCapacity;
243 if (newCapacity - MAX_ARRAY_SIZE > 0)
244 newCapacity = hugeCapacity(minCapacity);
245 // minCapacity is usually close to size, so this is a win:
246 elementData = Arrays.copyOf(elementData, newCapacity);
247 }
248
249 private static int hugeCapacity(int minCapacity) {
250 if (minCapacity < 0) // overflow
251 throw new OutOfMemoryError();
252 return (minCapacity > MAX_ARRAY_SIZE) ?
253 Integer.MAX_VALUE :
254 MAX_ARRAY_SIZE;
255 }
256
257 /**
258 * Returns the number of elements in this list.
259 *
260 * @return the number of elements in this list
261 */
262 public int size() {
263 return size;
264 }
265
266 /**
267 * Returns <tt>true</tt> if this list contains no elements.
268 *
269 * @return <tt>true</tt> if this list contains no elements
270 */
271 public boolean isEmpty() {
272 return size == 0;
273 }
274
275 /**
276 * Returns <tt>true</tt> if this list contains the specified element.
277 * More formally, returns <tt>true</tt> if and only if this list contains
278 * at least one element <tt>e</tt> such that
279 * <tt>(o==null ? e==null : o.equals(e))</tt>.
280 *
281 * @param o element whose presence in this list is to be tested
282 * @return <tt>true</tt> if this list contains the specified element
283 */
284 public boolean contains(Object o) {
285 return indexOf(o) >= 0;
286 }
287
288 /**
289 * Returns the index of the first occurrence of the specified element
290 * in this list, or -1 if this list does not contain the element.
291 * More formally, returns the lowest index <tt>i</tt> such that
292 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
293 * or -1 if there is no such index.
294 */
295 public int indexOf(Object o) {
296 if (o == null) {
297 for (int i = 0; i < size; i++)
298 if (elementData[i]==null)
299 return i;
300 } else {
301 for (int i = 0; i < size; i++)
302 if (o.equals(elementData[i]))
303 return i;
304 }
305 return -1;
306 }
307
308 /**
309 * Returns the index of the last occurrence of the specified element
310 * in this list, or -1 if this list does not contain the element.
311 * More formally, returns the highest index <tt>i</tt> such that
312 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
313 * or -1 if there is no such index.
314 */
315 public int lastIndexOf(Object o) {
316 if (o == null) {
317 for (int i = size-1; i >= 0; i--)
318 if (elementData[i]==null)
319 return i;
320 } else {
321 for (int i = size-1; i >= 0; i--)
322 if (o.equals(elementData[i]))
323 return i;
324 }
325 return -1;
326 }
327
328 /**
329 * Returns a shallow copy of this <tt>ArrayList</tt> instance. (The
330 * elements themselves are not copied.)
331 *
332 * @return a clone of this <tt>ArrayList</tt> instance
333 */
334 public Object clone() {
335 try {
336 ArrayList<?> v = (ArrayList<?>) super.clone();
337 v.elementData = Arrays.copyOf(elementData, size);
338 v.modCount = 0;
339 return v;
340 } catch (CloneNotSupportedException e) {
341 // this shouldn't happen, since we are Cloneable
342 throw new InternalError(e);
343 }
344 }
345
346 /**
347 * Returns an array containing all of the elements in this list
348 * in proper sequence (from first to last element).
349 *
350 * <p>The returned array will be "safe" in that no references to it are
351 * maintained by this list. (In other words, this method must allocate
352 * a new array). The caller is thus free to modify the returned array.
353 *
354 * <p>This method acts as bridge between array-based and collection-based
355 * APIs.
356 *
357 * @return an array containing all of the elements in this list in
358 * proper sequence
359 */
360 public Object[] toArray() {
361 return Arrays.copyOf(elementData, size);
362 }
363
364 /**
365 * Returns an array containing all of the elements in this list in proper
366 * sequence (from first to last element); the runtime type of the returned
367 * array is that of the specified array. If the list fits in the
368 * specified array, it is returned therein. Otherwise, a new array is
369 * allocated with the runtime type of the specified array and the size of
370 * this list.
371 *
372 * <p>If the list fits in the specified array with room to spare
373 * (i.e., the array has more elements than the list), the element in
374 * the array immediately following the end of the collection is set to
375 * <tt>null</tt>. (This is useful in determining the length of the
376 * list <i>only</i> if the caller knows that the list does not contain
377 * any null elements.)
378 *
379 * @param a the array into which the elements of the list are to
380 * be stored, if it is big enough; otherwise, a new array of the
381 * same runtime type is allocated for this purpose.
382 * @return an array containing the elements of the list
383 * @throws ArrayStoreException if the runtime type of the specified array
384 * is not a supertype of the runtime type of every element in
385 * this list
386 * @throws NullPointerException if the specified array is null
387 */
388 @SuppressWarnings("unchecked")
389 public <T> T[] toArray(T[] a) {
390 if (a.length < size)
391 // Make a new array of a's runtime type, but my contents:
392 return (T[]) Arrays.copyOf(elementData, size, a.getClass());
393 System.arraycopy(elementData, 0, a, 0, size);
394 if (a.length > size)
395 a[size] = null;
396 return a;
397 }
398
399 // Positional Access Operations
400
401 @SuppressWarnings("unchecked")
402 E elementData(int index) {
403 return (E) elementData[index];
404 }
405
406 /**
407 * Returns the element at the specified position in this list.
408 *
409 * @param index index of the element to return
410 * @return the element at the specified position in this list
411 * @throws IndexOutOfBoundsException {@inheritDoc}
412 */
413 public E get(int index) {
414 rangeCheck(index);
415
416 return elementData(index);
417 }
418
419 /**
420 * Replaces the element at the specified position in this list with
421 * the specified element.
422 *
423 * @param index index of the element to replace
424 * @param element element to be stored at the specified position
425 * @return the element previously at the specified position
426 * @throws IndexOutOfBoundsException {@inheritDoc}
427 */
428 public E set(int index, E element) {
429 rangeCheck(index);
430
431 E oldValue = elementData(index);
432 elementData[index] = element;
433 return oldValue;
434 }
435
436 /**
437 * Appends the specified element to the end of this list.
438 *
439 * @param e element to be appended to this list
440 * @return <tt>true</tt> (as specified by {@link Collection#add})
441 */
442 public boolean add(E e) {
443 ensureCapacityInternal(size + 1); // Increments modCount!!
444 elementData[size++] = e;
445 return true;
446 }
447
448 /**
449 * Inserts the specified element at the specified position in this
450 * list. Shifts the element currently at that position (if any) and
451 * any subsequent elements to the right (adds one to their indices).
452 *
453 * @param index index at which the specified element is to be inserted
454 * @param element element to be inserted
455 * @throws IndexOutOfBoundsException {@inheritDoc}
456 */
457 public void add(int index, E element) {
458 rangeCheckForAdd(index);
459
460 ensureCapacityInternal(size + 1); // Increments modCount!!
461 System.arraycopy(elementData, index, elementData, index + 1,
462 size - index);
463 elementData[index] = element;
464 size++;
465 }
466
467 /**
468 * Removes the element at the specified position in this list.
469 * Shifts any subsequent elements to the left (subtracts one from their
470 * indices).
471 *
472 * @param index the index of the element to be removed
473 * @return the element that was removed from the list
474 * @throws IndexOutOfBoundsException {@inheritDoc}
475 */
476 public E remove(int index) {
477 rangeCheck(index);
478
479 modCount++;
480 E oldValue = elementData(index);
481
482 int numMoved = size - index - 1;
483 if (numMoved > 0)
484 System.arraycopy(elementData, index+1, elementData, index,
485 numMoved);
486 elementData[--size] = null; // clear to let GC do its work
487
488 return oldValue;
489 }
490
491 /**
492 * Removes the first occurrence of the specified element from this list,
493 * if it is present. If the list does not contain the element, it is
494 * unchanged. More formally, removes the element with the lowest index
495 * <tt>i</tt> such that
496 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>
497 * (if such an element exists). Returns <tt>true</tt> if this list
498 * contained the specified element (or equivalently, if this list
499 * changed as a result of the call).
500 *
501 * @param o element to be removed from this list, if present
502 * @return <tt>true</tt> if this list contained the specified element
503 */
504 public boolean remove(Object o) {
505 if (o == null) {
506 for (int index = 0; index < size; index++)
507 if (elementData[index] == null) {
508 fastRemove(index);
509 return true;
510 }
511 } else {
512 for (int index = 0; index < size; index++)
513 if (o.equals(elementData[index])) {
514 fastRemove(index);
515 return true;
516 }
517 }
518 return false;
519 }
520
521 /*
522 * Private remove method that skips bounds checking and does not
523 * return the value removed.
524 */
525 private void fastRemove(int index) {
526 modCount++;
527 int numMoved = size - index - 1;
528 if (numMoved > 0)
529 System.arraycopy(elementData, index+1, elementData, index,
530 numMoved);
531 elementData[--size] = null; // clear to let GC do its work
532 }
533
534 /**
535 * Removes all of the elements from this list. The list will
536 * be empty after this call returns.
537 */
538 public void clear() {
539 modCount++;
540
541 // clear to let GC do its work
542 for (int i = 0; i < size; i++)
543 elementData[i] = null;
544
545 size = 0;
546 }
547
548 /**
549 * Appends all of the elements in the specified collection to the end of
550 * this list, in the order that they are returned by the
551 * specified collection's Iterator. The behavior of this operation is
552 * undefined if the specified collection is modified while the operation
553 * is in progress. (This implies that the behavior of this call is
554 * undefined if the specified collection is this list, and this
555 * list is nonempty.)
556 *
557 * @param c collection containing elements to be added to this list
558 * @return <tt>true</tt> if this list changed as a result of the call
559 * @throws NullPointerException if the specified collection is null
560 */
561 public boolean addAll(Collection<? extends E> c) {
562 Object[] a = c.toArray();
563 int numNew = a.length;
564 ensureCapacityInternal(size + numNew); // Increments modCount
565 System.arraycopy(a, 0, elementData, size, numNew);
566 size += numNew;
567 return numNew != 0;
568 }
569
570 /**
571 * Inserts all of the elements in the specified collection into this
572 * list, starting at the specified position. Shifts the element
573 * currently at that position (if any) and any subsequent elements to
574 * the right (increases their indices). The new elements will appear
575 * in the list in the order that they are returned by the
576 * specified collection's iterator.
577 *
578 * @param index index at which to insert the first element from the
579 * specified collection
580 * @param c collection containing elements to be added to this list
581 * @return <tt>true</tt> if this list changed as a result of the call
582 * @throws IndexOutOfBoundsException {@inheritDoc}
583 * @throws NullPointerException if the specified collection is null
584 */
585 public boolean addAll(int index, Collection<? extends E> c) {
586 rangeCheckForAdd(index);
587
588 Object[] a = c.toArray();
589 int numNew = a.length;
590 ensureCapacityInternal(size + numNew); // Increments modCount
591
592 int numMoved = size - index;
593 if (numMoved > 0)
594 System.arraycopy(elementData, index, elementData, index + numNew,
595 numMoved);
596
597 System.arraycopy(a, 0, elementData, index, numNew);
598 size += numNew;
599 return numNew != 0;
600 }
601
602 /**
603 * Removes from this list all of the elements whose index is between
604 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
605 * Shifts any succeeding elements to the left (reduces their index).
606 * This call shortens the list by {@code (toIndex - fromIndex)} elements.
607 * (If {@code toIndex==fromIndex}, this operation has no effect.)
608 *
609 * @throws IndexOutOfBoundsException if {@code fromIndex} or
610 * {@code toIndex} is out of range
611 * ({@code fromIndex < 0 ||
612 * toIndex > size() ||
613 * toIndex < fromIndex})
614 */
615 protected void removeRange(int fromIndex, int toIndex) {
616 if (fromIndex > toIndex) {
617 throw new IndexOutOfBoundsException(
618 outOfBoundsMsg(fromIndex, toIndex));
619 }
620 modCount++;
621 int numMoved = size - toIndex;
622 System.arraycopy(elementData, toIndex, elementData, fromIndex,
623 numMoved);
624
625 // clear to let GC do its work
626 int newSize = size - (toIndex-fromIndex);
627 for (int i = newSize; i < size; i++) {
628 elementData[i] = null;
629 }
630 size = newSize;
631 }
632
633 /**
634 * Checks if the given index is in range. If not, throws an appropriate
635 * runtime exception. This method does *not* check if the index is
636 * negative: It is always used immediately prior to an array access,
637 * which throws an ArrayIndexOutOfBoundsException if index is negative.
638 */
639 private void rangeCheck(int index) {
640 if (index >= size)
641 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
642 }
643
644 /**
645 * A version of rangeCheck used by add and addAll.
646 */
647 private void rangeCheckForAdd(int index) {
648 if (index > size || index < 0)
649 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
650 }
651
652 /**
653 * Constructs an IndexOutOfBoundsException detail message.
654 * Of the many possible refactorings of the error handling code,
655 * this "outlining" performs best with both server and client VMs.
656 */
657 private String outOfBoundsMsg(int index) {
658 return "Index: "+index+", Size: "+size;
659 }
660
661 /**
662 * A version used in checking (fromIndex > toIndex) condition
663 */
664 private static String outOfBoundsMsg(int fromIndex, int toIndex) {
665 return "From Index: " + fromIndex + " > To Index: " + toIndex;
666 }
667
668 /**
669 * Removes from this list all of its elements that are contained in the
670 * specified collection.
671 *
672 * @param c collection containing elements to be removed from this list
673 * @return {@code true} if this list changed as a result of the call
674 * @throws ClassCastException if the class of an element of this list
675 * is incompatible with the specified collection
676 * (<a href="Collection.html#optional-restrictions">optional</a>)
677 * @throws NullPointerException if this list contains a null element and the
678 * specified collection does not permit null elements
679 * (<a href="Collection.html#optional-restrictions">optional</a>),
680 * or if the specified collection is null
681 * @see Collection#contains(Object)
682 */
683 public boolean removeAll(Collection<?> c) {
684 Objects.requireNonNull(c);
685 return batchRemove(c, false);
686 }
687
688 /**
689 * Retains only the elements in this list that are contained in the
690 * specified collection. In other words, removes from this list all
691 * of its elements that are not contained in the specified collection.
692 *
693 * @param c collection containing elements to be retained in this list
694 * @return {@code true} if this list changed as a result of the call
695 * @throws ClassCastException if the class of an element of this list
696 * is incompatible with the specified collection
697 * (<a href="Collection.html#optional-restrictions">optional</a>)
698 * @throws NullPointerException if this list contains a null element and the
699 * specified collection does not permit null elements
700 * (<a href="Collection.html#optional-restrictions">optional</a>),
701 * or if the specified collection is null
702 * @see Collection#contains(Object)
703 */
704 public boolean retainAll(Collection<?> c) {
705 Objects.requireNonNull(c);
706 return batchRemove(c, true);
707 }
708
709 private boolean batchRemove(Collection<?> c, boolean complement) {
710 final Object[] elementData = this.elementData;
711 int r = 0, w = 0;
712 boolean modified = false;
713 try {
714 for (; r < size; r++)
715 if (c.contains(elementData[r]) == complement)
716 elementData[w++] = elementData[r];
717 } finally {
718 // Preserve behavioral compatibility with AbstractCollection,
719 // even if c.contains() throws.
720 if (r != size) {
721 System.arraycopy(elementData, r,
722 elementData, w,
723 size - r);
724 w += size - r;
725 }
726 if (w != size) {
727 // clear to let GC do its work
728 for (int i = w; i < size; i++)
729 elementData[i] = null;
730 modCount += size - w;
731 size = w;
732 modified = true;
733 }
734 }
735 return modified;
736 }
737
738 /**
739 * Save the state of the <tt>ArrayList</tt> instance to a stream (that
740 * is, serialize it).
741 *
742 * @serialData The length of the array backing the <tt>ArrayList</tt>
743 * instance is emitted (int), followed by all of its elements
744 * (each an <tt>Object</tt>) in the proper order.
745 */
746 private void writeObject(java.io.ObjectOutputStream s)
747 throws java.io.IOException{
748 // Write out element count, and any hidden stuff
749 int expectedModCount = modCount;
750 s.defaultWriteObject();
751
752 // Write out size as capacity for behavioural compatibility with clone()
753 s.writeInt(size);
754
755 // Write out all elements in the proper order.
756 for (int i=0; i<size; i++) {
757 s.writeObject(elementData[i]);
758 }
759
760 if (modCount != expectedModCount) {
761 throw new ConcurrentModificationException();
762 }
763 }
764
765 /**
766 * Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
767 * deserialize it).
768 */
769 private void readObject(java.io.ObjectInputStream s)
770 throws java.io.IOException, ClassNotFoundException {
771 elementData = EMPTY_ELEMENTDATA;
772
773 // Read in size, and any hidden stuff
774 s.defaultReadObject();
775
776 // Read in capacity
777 s.readInt(); // ignored
778
779 if (size > 0) {
780 // be like clone(), allocate array based upon size not capacity
781 ensureCapacityInternal(size);
782
783 Object[] a = elementData;
784 // Read in all elements in the proper order.
785 for (int i=0; i<size; i++) {
786 a[i] = s.readObject();
787 }
788 }
789 }
790
791 /**
792 * Returns a list iterator over the elements in this list (in proper
793 * sequence), starting at the specified position in the list.
794 * The specified index indicates the first element that would be
795 * returned by an initial call to {@link ListIterator#next next}.
796 * An initial call to {@link ListIterator#previous previous} would
797 * return the element with the specified index minus one.
798 *
799 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
800 *
801 * @throws IndexOutOfBoundsException {@inheritDoc}
802 */
803 public ListIterator<E> listIterator(int index) {
804 if (index < 0 || index > size)
805 throw new IndexOutOfBoundsException("Index: "+index);
806 return new ListItr(index);
807 }
808
809 /**
810 * Returns a list iterator over the elements in this list (in proper
811 * sequence).
812 *
813 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
814 *
815 * @see #listIterator(int)
816 */
817 public ListIterator<E> listIterator() {
818 return new ListItr(0);
819 }
820
821 /**
822 * Returns an iterator over the elements in this list in proper sequence.
823 *
824 * <p>The returned iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
825 *
826 * @return an iterator over the elements in this list in proper sequence
827 */
828 public Iterator<E> iterator() {
829 return new Itr();
830 }
831
832 /**
833 * An optimized version of AbstractList.Itr
834 */
835 private class Itr implements Iterator<E> {
836 int cursor; // index of next element to return
837 int lastRet = -1; // index of last element returned; -1 if no such
838 int expectedModCount = modCount;
839
840 public boolean hasNext() {
841 return cursor != size;
842 }
843
844 @SuppressWarnings("unchecked")
845 public E next() {
846 checkForComodification();
847 int i = cursor;
848 if (i >= size)
849 throw new NoSuchElementException();
850 Object[] elementData = ArrayList.this.elementData;
851 if (i >= elementData.length)
852 throw new ConcurrentModificationException();
853 cursor = i + 1;
854 return (E) elementData[lastRet = i];
855 }
856
857 public void remove() {
858 if (lastRet < 0)
859 throw new IllegalStateException();
860 checkForComodification();
861
862 try {
863 ArrayList.this.remove(lastRet);
864 cursor = lastRet;
865 lastRet = -1;
866 expectedModCount = modCount;
867 } catch (IndexOutOfBoundsException ex) {
868 throw new ConcurrentModificationException();
869 }
870 }
871
872 @Override
873 @SuppressWarnings("unchecked")
874 public void forEachRemaining(Consumer<? super E> consumer) {
875 Objects.requireNonNull(consumer);
876 final int size = ArrayList.this.size;
877 int i = cursor;
878 if (i >= size) {
879 return;
880 }
881 final Object[] elementData = ArrayList.this.elementData;
882 if (i >= elementData.length) {
883 throw new ConcurrentModificationException();
884 }
885 while (i != size && modCount == expectedModCount) {
886 consumer.accept((E) elementData[i++]);
887 }
888 // update once at end of iteration to reduce heap write traffic
889 cursor = i;
890 lastRet = i - 1;
891 checkForComodification();
892 }
893
894 final void checkForComodification() {
895 if (modCount != expectedModCount)
896 throw new ConcurrentModificationException();
897 }
898 }
899
900 /**
901 * An optimized version of AbstractList.ListItr
902 */
903 private class ListItr extends Itr implements ListIterator<E> {
904 ListItr(int index) {
905 super();
906 cursor = index;
907 }
908
909 public boolean hasPrevious() {
910 return cursor != 0;
911 }
912
913 public int nextIndex() {
914 return cursor;
915 }
916
917 public int previousIndex() {
918 return cursor - 1;
919 }
920
921 @SuppressWarnings("unchecked")
922 public E previous() {
923 checkForComodification();
924 int i = cursor - 1;
925 if (i < 0)
926 throw new NoSuchElementException();
927 Object[] elementData = ArrayList.this.elementData;
928 if (i >= elementData.length)
929 throw new ConcurrentModificationException();
930 cursor = i;
931 return (E) elementData[lastRet = i];
932 }
933
934 public void set(E e) {
935 if (lastRet < 0)
936 throw new IllegalStateException();
937 checkForComodification();
938
939 try {
940 ArrayList.this.set(lastRet, e);
941 } catch (IndexOutOfBoundsException ex) {
942 throw new ConcurrentModificationException();
943 }
944 }
945
946 public void add(E e) {
947 checkForComodification();
948
949 try {
950 int i = cursor;
951 ArrayList.this.add(i, e);
952 cursor = i + 1;
953 lastRet = -1;
954 expectedModCount = modCount;
955 } catch (IndexOutOfBoundsException ex) {
956 throw new ConcurrentModificationException();
957 }
958 }
959 }
960
961 /**
962 * Returns a view of the portion of this list between the specified
963 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. (If
964 * {@code fromIndex} and {@code toIndex} are equal, the returned list is
965 * empty.) The returned list is backed by this list, so non-structural
966 * changes in the returned list are reflected in this list, and vice-versa.
967 * The returned list supports all of the optional list operations.
968 *
969 * <p>This method eliminates the need for explicit range operations (of
970 * the sort that commonly exist for arrays). Any operation that expects
971 * a list can be used as a range operation by passing a subList view
972 * instead of a whole list. For example, the following idiom
973 * removes a range of elements from a list:
974 * <pre>
975 * list.subList(from, to).clear();
976 * </pre>
977 * Similar idioms may be constructed for {@link #indexOf(Object)} and
978 * {@link #lastIndexOf(Object)}, and all of the algorithms in the
979 * {@link Collections} class can be applied to a subList.
980 *
981 * <p>The semantics of the list returned by this method become undefined if
982 * the backing list (i.e., this list) is <i>structurally modified</i> in
983 * any way other than via the returned list. (Structural modifications are
984 * those that change the size of this list, or otherwise perturb it in such
985 * a fashion that iterations in progress may yield incorrect results.)
986 *
987 * @throws IndexOutOfBoundsException {@inheritDoc}
988 * @throws IllegalArgumentException {@inheritDoc}
989 */
990 public List<E> subList(int fromIndex, int toIndex) {
991 subListRangeCheck(fromIndex, toIndex, size);
992 return new SubList(this, 0, fromIndex, toIndex);
993 }
994
995 static void subListRangeCheck(int fromIndex, int toIndex, int size) {
996 if (fromIndex < 0)
997 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
998 if (toIndex > size)
999 throw new IndexOutOfBoundsException("toIndex = " + toIndex);
1000 if (fromIndex > toIndex)
1001 throw new IllegalArgumentException("fromIndex(" + fromIndex +
1002 ") > toIndex(" + toIndex + ")");
1003 }
1004
1005 private class SubList extends AbstractList<E> implements RandomAccess {
1006 private final AbstractList<E> parent;
1007 private final int parentOffset;
1008 private final int offset;
1009 int size;
1010
1011 SubList(AbstractList<E> parent,
1012 int offset, int fromIndex, int toIndex) {
1013 this.parent = parent;
1014 this.parentOffset = fromIndex;
1015 this.offset = offset + fromIndex;
1016 this.size = toIndex - fromIndex;
1017 this.modCount = ArrayList.this.modCount;
1018 }
1019
1020 public E set(int index, E e) {
1021 rangeCheck(index);
1022 checkForComodification();
1023 E oldValue = ArrayList.this.elementData(offset + index);
1024 ArrayList.this.elementData[offset + index] = e;
1025 return oldValue;
1026 }
1027
1028 public E get(int index) {
1029 rangeCheck(index);
1030 checkForComodification();
1031 return ArrayList.this.elementData(offset + index);
1032 }
1033
1034 public int size() {
1035 checkForComodification();
1036 return this.size;
1037 }
1038
1039 public void add(int index, E e) {
1040 rangeCheckForAdd(index);
1041 checkForComodification();
1042 parent.add(parentOffset + index, e);
1043 this.modCount = parent.modCount;
1044 this.size++;
1045 }
1046
1047 public E remove(int index) {
1048 rangeCheck(index);
1049 checkForComodification();
1050 E result = parent.remove(parentOffset + index);
1051 this.modCount = parent.modCount;
1052 this.size--;
1053 return result;
1054 }
1055
1056 protected void removeRange(int fromIndex, int toIndex) {
1057 checkForComodification();
1058 parent.removeRange(parentOffset + fromIndex,
1059 parentOffset + toIndex);
1060 this.modCount = parent.modCount;
1061 this.size -= toIndex - fromIndex;
1062 }
1063
1064 public boolean addAll(Collection<? extends E> c) {
1065 return addAll(this.size, c);
1066 }
1067
1068 public boolean addAll(int index, Collection<? extends E> c) {
1069 rangeCheckForAdd(index);
1070 int cSize = c.size();
1071 if (cSize==0)
1072 return false;
1073
1074 checkForComodification();
1075 parent.addAll(parentOffset + index, c);
1076 this.modCount = parent.modCount;
1077 this.size += cSize;
1078 return true;
1079 }
1080
1081 public Iterator<E> iterator() {
1082 return listIterator();
1083 }
1084
1085 public ListIterator<E> listIterator(final int index) {
1086 checkForComodification();
1087 rangeCheckForAdd(index);
1088 final int offset = this.offset;
1089
1090 return new ListIterator<E>() {
1091 int cursor = index;
1092 int lastRet = -1;
1093 int expectedModCount = ArrayList.this.modCount;
1094
1095 public boolean hasNext() {
1096 return cursor != SubList.this.size;
1097 }
1098
1099 @SuppressWarnings("unchecked")
1100 public E next() {
1101 checkForComodification();
1102 int i = cursor;
1103 if (i >= SubList.this.size)
1104 throw new NoSuchElementException();
1105 Object[] elementData = ArrayList.this.elementData;
1106 if (offset + i >= elementData.length)
1107 throw new ConcurrentModificationException();
1108 cursor = i + 1;
1109 return (E) elementData[offset + (lastRet = i)];
1110 }
1111
1112 public boolean hasPrevious() {
1113 return cursor != 0;
1114 }
1115
1116 @SuppressWarnings("unchecked")
1117 public E previous() {
1118 checkForComodification();
1119 int i = cursor - 1;
1120 if (i < 0)
1121 throw new NoSuchElementException();
1122 Object[] elementData = ArrayList.this.elementData;
1123 if (offset + i >= elementData.length)
1124 throw new ConcurrentModificationException();
1125 cursor = i;
1126 return (E) elementData[offset + (lastRet = i)];
1127 }
1128
1129 @SuppressWarnings("unchecked")
1130 public void forEachRemaining(Consumer<? super E> consumer) {
1131 Objects.requireNonNull(consumer);
1132 final int size = SubList.this.size;
1133 int i = cursor;
1134 if (i >= size) {
1135 return;
1136 }
1137 final Object[] elementData = ArrayList.this.elementData;
1138 if (offset + i >= elementData.length) {
1139 throw new ConcurrentModificationException();
1140 }
1141 while (i != size && modCount == expectedModCount) {
1142 consumer.accept((E) elementData[offset + (i++)]);
1143 }
1144 // update once at end of iteration to reduce heap write traffic
1145 lastRet = cursor = i;
1146 checkForComodification();
1147 }
1148
1149 public int nextIndex() {
1150 return cursor;
1151 }
1152
1153 public int previousIndex() {
1154 return cursor - 1;
1155 }
1156
1157 public void remove() {
1158 if (lastRet < 0)
1159 throw new IllegalStateException();
1160 checkForComodification();
1161
1162 try {
1163 SubList.this.remove(lastRet);
1164 cursor = lastRet;
1165 lastRet = -1;
1166 expectedModCount = ArrayList.this.modCount;
1167 } catch (IndexOutOfBoundsException ex) {
1168 throw new ConcurrentModificationException();
1169 }
1170 }
1171
1172 public void set(E e) {
1173 if (lastRet < 0)
1174 throw new IllegalStateException();
1175 checkForComodification();
1176
1177 try {
1178 ArrayList.this.set(offset + lastRet, e);
1179 } catch (IndexOutOfBoundsException ex) {
1180 throw new ConcurrentModificationException();
1181 }
1182 }
1183
1184 public void add(E e) {
1185 checkForComodification();
1186
1187 try {
1188 int i = cursor;
1189 SubList.this.add(i, e);
1190 cursor = i + 1;
1191 lastRet = -1;
1192 expectedModCount = ArrayList.this.modCount;
1193 } catch (IndexOutOfBoundsException ex) {
1194 throw new ConcurrentModificationException();
1195 }
1196 }
1197
1198 final void checkForComodification() {
1199 if (expectedModCount != ArrayList.this.modCount)
1200 throw new ConcurrentModificationException();
1201 }
1202 };
1203 }
1204
1205 public List<E> subList(int fromIndex, int toIndex) {
1206 subListRangeCheck(fromIndex, toIndex, size);
1207 return new SubList(this, offset, fromIndex, toIndex);
1208 }
1209
1210 private void rangeCheck(int index) {
1211 if (index < 0 || index >= this.size)
1212 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
1213 }
1214
1215 private void rangeCheckForAdd(int index) {
1216 if (index < 0 || index > this.size)
1217 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
1218 }
1219
1220 private String outOfBoundsMsg(int index) {
1221 return "Index: "+index+", Size: "+this.size;
1222 }
1223
1224 private void checkForComodification() {
1225 if (ArrayList.this.modCount != this.modCount)
1226 throw new ConcurrentModificationException();
1227 }
1228
1229 public Spliterator<E> spliterator() {
1230 checkForComodification();
1231 return new ArrayListSpliterator<>(ArrayList.this, offset,
1232 offset + this.size, this.modCount);
1233 }
1234 }
1235
1236 @Override
1237 public void forEach(Consumer<? super E> action) {
1238 Objects.requireNonNull(action);
1239 final int expectedModCount = modCount;
1240 @SuppressWarnings("unchecked")
1241 final E[] elementData = (E[]) this.elementData;
1242 final int size = this.size;
1243 for (int i=0; modCount == expectedModCount && i < size; i++) {
1244 action.accept(elementData[i]);
1245 }
1246 if (modCount != expectedModCount) {
1247 throw new ConcurrentModificationException();
1248 }
1249 }
1250
1251 /**
1252 * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
1253 * and <em>fail-fast</em> {@link Spliterator} over the elements in this
1254 * list.
1255 *
1256 * <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
1257 * {@link Spliterator#SUBSIZED}, and {@link Spliterator#ORDERED}.
1258 * Overriding implementations should document the reporting of additional
1259 * characteristic values.
1260 *
1261 * @return a {@code Spliterator} over the elements in this list
1262 * @since 1.8
1263 */
1264 @Override
1265 public Spliterator<E> spliterator() {
1266 return new ArrayListSpliterator<>(this, 0, -1, 0);
1267 }
1268
1269 /** Index-based split-by-two, lazily initialized Spliterator */
1270 static final class ArrayListSpliterator<E> implements Spliterator<E> {
1271
1272 /*
1273 * If ArrayLists were immutable, or structurally immutable (no
1274 * adds, removes, etc), we could implement their spliterators
1275 * with Arrays.spliterator. Instead we detect as much
1276 * interference during traversal as practical without
1277 * sacrificing much performance. We rely primarily on
1278 * modCounts. These are not guaranteed to detect concurrency
1279 * violations, and are sometimes overly conservative about
1280 * within-thread interference, but detect enough problems to
1281 * be worthwhile in practice. To carry this out, we (1) lazily
1282 * initialize fence and expectedModCount until the latest
1283 * point that we need to commit to the state we are checking
1284 * against; thus improving precision. (This doesn't apply to
1285 * SubLists, that create spliterators with current non-lazy
1286 * values). (2) We perform only a single
1287 * ConcurrentModificationException check at the end of forEach
1288 * (the most performance-sensitive method). When using forEach
1289 * (as opposed to iterators), we can normally only detect
1290 * interference after actions, not before. Further
1291 * CME-triggering checks apply to all other possible
1292 * violations of assumptions for example null or too-small
1293 * elementData array given its size(), that could only have
1294 * occurred due to interference. This allows the inner loop
1295 * of forEach to run without any further checks, and
1296 * simplifies lambda-resolution. While this does entail a
1297 * number of checks, note that in the common case of
1298 * list.stream().forEach(a), no checks or other computation
1299 * occur anywhere other than inside forEach itself. The other
1300 * less-often-used methods cannot take advantage of most of
1301 * these streamlinings.
1302 */
1303
1304 private final ArrayList<E> list;
1305 private int index; // current index, modified on advance/split
1306 private int fence; // -1 until used; then one past last index
1307 private int expectedModCount; // initialized when fence set
1308
1309 /** Create new spliterator covering the given range */
1310 ArrayListSpliterator(ArrayList<E> list, int origin, int fence,
1311 int expectedModCount) {
1312 this.list = list; // OK if null unless traversed
1313 this.index = origin;
1314 this.fence = fence;
1315 this.expectedModCount = expectedModCount;
1316 }
1317
1318 private int getFence() { // initialize fence to size on first use
1319 int hi; // (a specialized variant appears in method forEach)
1320 ArrayList<E> lst;
1321 if ((hi = fence) < 0) {
1322 if ((lst = list) == null)
1323 hi = fence = 0;
1324 else {
1325 expectedModCount = lst.modCount;
1326 hi = fence = lst.size;
1327 }
1328 }
1329 return hi;
1330 }
1331
1332 public ArrayListSpliterator<E> trySplit() {
1333 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1334 return (lo >= mid) ? null : // divide range in half unless too small
1335 new ArrayListSpliterator<>(list, lo, index = mid,
1336 expectedModCount);
1337 }
1338
1339 public boolean tryAdvance(Consumer<? super E> action) {
1340 if (action == null)
1341 throw new NullPointerException();
1342 int hi = getFence(), i = index;
1343 if (i < hi) {
1344 index = i + 1;
1345 @SuppressWarnings("unchecked") E e = (E)list.elementData[i];
1346 action.accept(e);
1347 if (list.modCount != expectedModCount)
1348 throw new ConcurrentModificationException();
1349 return true;
1350 }
1351 return false;
1352 }
1353
1354 public void forEachRemaining(Consumer<? super E> action) {
1355 int i, hi, mc; // hoist accesses and checks from loop
1356 ArrayList<E> lst; Object[] a;
1357 if (action == null)
1358 throw new NullPointerException();
1359 if ((lst = list) != null && (a = lst.elementData) != null) {
1360 if ((hi = fence) < 0) {
1361 mc = lst.modCount;
1362 hi = lst.size;
1363 }
1364 else
1365 mc = expectedModCount;
1366 if ((i = index) >= 0 && (index = hi) <= a.length) {
1367 for (; i < hi; ++i) {
1368 @SuppressWarnings("unchecked") E e = (E) a[i];
1369 action.accept(e);
1370 }
1371 if (lst.modCount == mc)
1372 return;
1373 }
1374 }
1375 throw new ConcurrentModificationException();
1376 }
1377
1378 public long estimateSize() {
1379 return (long) (getFence() - index);
1380 }
1381
1382 public int characteristics() {
1383 return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
1384 }
1385 }
1386
1387 @Override
1388 public boolean removeIf(Predicate<? super E> filter) {
1389 Objects.requireNonNull(filter);
1390 // figure out which elements are to be removed
1391 // any exception thrown from the filter predicate at this stage
1392 // will leave the collection unmodified
1393 int removeCount = 0;
1394 final BitSet removeSet = new BitSet(size);
1395 final int expectedModCount = modCount;
1396 final int size = this.size;
1397 for (int i=0; modCount == expectedModCount && i < size; i++) {
1398 @SuppressWarnings("unchecked")
1399 final E element = (E) elementData[i];
1400 if (filter.test(element)) {
1401 removeSet.set(i);
1402 removeCount++;
1403 }
1404 }
1405 if (modCount != expectedModCount) {
1406 throw new ConcurrentModificationException();
1407 }
1408
1409 // shift surviving elements left over the spaces left by removed elements
1410 final boolean anyToRemove = removeCount > 0;
1411 if (anyToRemove) {
1412 final int newSize = size - removeCount;
1413 for (int i=0, j=0; (i < size) && (j < newSize); i++, j++) {
1414 i = removeSet.nextClearBit(i);
1415 elementData[j] = elementData[i];
1416 }
1417 for (int k=newSize; k < size; k++) {
1418 elementData[k] = null; // Let gc do its work
1419 }
1420 this.size = newSize;
1421 if (modCount != expectedModCount) {
1422 throw new ConcurrentModificationException();
1423 }
1424 modCount++;
1425 }
1426
1427 return anyToRemove;
1428 }
1429
1430 @Override
1431 @SuppressWarnings("unchecked")
1432 public void replaceAll(UnaryOperator<E> operator) {
1433 Objects.requireNonNull(operator);
1434 final int expectedModCount = modCount;
1435 final int size = this.size;
1436 for (int i=0; modCount == expectedModCount && i < size; i++) {
1437 elementData[i] = operator.apply((E) elementData[i]);
1438 }
1439 if (modCount != expectedModCount) {
1440 throw new ConcurrentModificationException();
1441 }
1442 modCount++;
1443 }
1444
1445 @Override
1446 @SuppressWarnings("unchecked")
1447 public void sort(Comparator<? super E> c) {
1448 final int expectedModCount = modCount;
1449 Arrays.sort((E[]) elementData, 0, size, c);
1450 if (modCount != expectedModCount) {
1451 throw new ConcurrentModificationException();
1452 }
1453 modCount++;
1454 }
1455 }