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 "From Index: " + fromIndex + " > To Index: " + toIndex);
619 modCount++;
620 int numMoved = size - toIndex;
621 System.arraycopy(elementData, toIndex, elementData, fromIndex,
622 numMoved);
623
624 // clear to let GC do its work
625 int newSize = size - (toIndex-fromIndex);
626 for (int i = newSize; i < size; i++) {
627 elementData[i] = null;
628 }
629 size = newSize;
630 }
631
632 /**
633 * Checks if the given index is in range. If not, throws an appropriate
634 * runtime exception. This method does *not* check if the index is
635 * negative: It is always used immediately prior to an array access,
636 * which throws an ArrayIndexOutOfBoundsException if index is negative.
637 */
638 private void rangeCheck(int index) {
639 if (index >= size)
640 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
641 }
642
643 /**
644 * A version of rangeCheck used by add and addAll.
645 */
646 private void rangeCheckForAdd(int index) {
647 if (index > size || index < 0)
648 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
649 }
650
651 /**
652 * Constructs an IndexOutOfBoundsException detail message.
653 * Of the many possible refactorings of the error handling code,
654 * this "outlining" performs best with both server and client VMs.
655 */
656 private String outOfBoundsMsg(int index) {
657 return "Index: "+index+", Size: "+size;
658 }
659
660 /**
661 * Removes from this list all of its elements that are contained in the
662 * specified collection.
663 *
664 * @param c collection containing elements to be removed from this list
665 * @return {@code true} if this list changed as a result of the call
666 * @throws ClassCastException if the class of an element of this list
667 * is incompatible with the specified collection
668 * (<a href="Collection.html#optional-restrictions">optional</a>)
669 * @throws NullPointerException if this list contains a null element and the
670 * specified collection does not permit null elements
671 * (<a href="Collection.html#optional-restrictions">optional</a>),
672 * or if the specified collection is null
673 * @see Collection#contains(Object)
674 */
675 public boolean removeAll(Collection<?> c) {
676 Objects.requireNonNull(c);
677 return batchRemove(c, false);
678 }
679
680 /**
681 * Retains only the elements in this list that are contained in the
682 * specified collection. In other words, removes from this list all
683 * of its elements that are not contained in the specified collection.
684 *
685 * @param c collection containing elements to be retained in this list
686 * @return {@code true} if this list changed as a result of the call
687 * @throws ClassCastException if the class of an element of this list
688 * is incompatible with the specified collection
689 * (<a href="Collection.html#optional-restrictions">optional</a>)
690 * @throws NullPointerException if this list contains a null element and the
691 * specified collection does not permit null elements
692 * (<a href="Collection.html#optional-restrictions">optional</a>),
693 * or if the specified collection is null
694 * @see Collection#contains(Object)
695 */
696 public boolean retainAll(Collection<?> c) {
697 Objects.requireNonNull(c);
698 return batchRemove(c, true);
699 }
700
701 private boolean batchRemove(Collection<?> c, boolean complement) {
702 final Object[] elementData = this.elementData;
703 int r = 0, w = 0;
704 boolean modified = false;
705 try {
706 for (; r < size; r++)
707 if (c.contains(elementData[r]) == complement)
708 elementData[w++] = elementData[r];
709 } finally {
710 // Preserve behavioral compatibility with AbstractCollection,
711 // even if c.contains() throws.
712 if (r != size) {
713 System.arraycopy(elementData, r,
714 elementData, w,
715 size - r);
716 w += size - r;
717 }
718 if (w != size) {
719 // clear to let GC do its work
720 for (int i = w; i < size; i++)
721 elementData[i] = null;
722 modCount += size - w;
723 size = w;
724 modified = true;
725 }
726 }
727 return modified;
728 }
729
730 /**
731 * Save the state of the <tt>ArrayList</tt> instance to a stream (that
732 * is, serialize it).
733 *
734 * @serialData The length of the array backing the <tt>ArrayList</tt>
735 * instance is emitted (int), followed by all of its elements
736 * (each an <tt>Object</tt>) in the proper order.
737 */
738 private void writeObject(java.io.ObjectOutputStream s)
739 throws java.io.IOException{
740 // Write out element count, and any hidden stuff
741 int expectedModCount = modCount;
742 s.defaultWriteObject();
743
744 // Write out size as capacity for behavioural compatibility with clone()
745 s.writeInt(size);
746
747 // Write out all elements in the proper order.
748 for (int i=0; i<size; i++) {
749 s.writeObject(elementData[i]);
750 }
751
752 if (modCount != expectedModCount) {
753 throw new ConcurrentModificationException();
754 }
755 }
756
757 /**
758 * Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
759 * deserialize it).
760 */
761 private void readObject(java.io.ObjectInputStream s)
762 throws java.io.IOException, ClassNotFoundException {
763 elementData = EMPTY_ELEMENTDATA;
764
765 // Read in size, and any hidden stuff
766 s.defaultReadObject();
767
768 // Read in capacity
769 s.readInt(); // ignored
770
771 if (size > 0) {
772 // be like clone(), allocate array based upon size not capacity
773 ensureCapacityInternal(size);
774
775 Object[] a = elementData;
776 // Read in all elements in the proper order.
777 for (int i=0; i<size; i++) {
778 a[i] = s.readObject();
779 }
780 }
781 }
782
783 /**
784 * Returns a list iterator over the elements in this list (in proper
785 * sequence), starting at the specified position in the list.
786 * The specified index indicates the first element that would be
787 * returned by an initial call to {@link ListIterator#next next}.
788 * An initial call to {@link ListIterator#previous previous} would
789 * return the element with the specified index minus one.
790 *
791 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
792 *
793 * @throws IndexOutOfBoundsException {@inheritDoc}
794 */
795 public ListIterator<E> listIterator(int index) {
796 if (index < 0 || index > size)
797 throw new IndexOutOfBoundsException("Index: "+index);
798 return new ListItr(index);
799 }
800
801 /**
802 * Returns a list iterator over the elements in this list (in proper
803 * sequence).
804 *
805 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
806 *
807 * @see #listIterator(int)
808 */
809 public ListIterator<E> listIterator() {
810 return new ListItr(0);
811 }
812
813 /**
814 * Returns an iterator over the elements in this list in proper sequence.
815 *
816 * <p>The returned iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
817 *
818 * @return an iterator over the elements in this list in proper sequence
819 */
820 public Iterator<E> iterator() {
821 return new Itr();
822 }
823
824 /**
825 * An optimized version of AbstractList.Itr
826 */
827 private class Itr implements Iterator<E> {
828 int cursor; // index of next element to return
829 int lastRet = -1; // index of last element returned; -1 if no such
830 int expectedModCount = modCount;
831
832 public boolean hasNext() {
833 return cursor != size;
834 }
835
836 @SuppressWarnings("unchecked")
837 public E next() {
838 checkForComodification();
839 int i = cursor;
840 if (i >= size)
841 throw new NoSuchElementException();
842 Object[] elementData = ArrayList.this.elementData;
843 if (i >= elementData.length)
844 throw new ConcurrentModificationException();
845 cursor = i + 1;
846 return (E) elementData[lastRet = i];
847 }
848
849 public void remove() {
850 if (lastRet < 0)
851 throw new IllegalStateException();
852 checkForComodification();
853
854 try {
855 ArrayList.this.remove(lastRet);
856 cursor = lastRet;
857 lastRet = -1;
858 expectedModCount = modCount;
859 } catch (IndexOutOfBoundsException ex) {
860 throw new ConcurrentModificationException();
861 }
862 }
863
864 @Override
865 @SuppressWarnings("unchecked")
866 public void forEachRemaining(Consumer<? super E> consumer) {
867 Objects.requireNonNull(consumer);
868 final int size = ArrayList.this.size;
869 int i = cursor;
870 if (i >= size) {
871 return;
872 }
873 final Object[] elementData = ArrayList.this.elementData;
874 if (i >= elementData.length) {
875 throw new ConcurrentModificationException();
876 }
877 while (i != size && modCount == expectedModCount) {
878 consumer.accept((E) elementData[i++]);
879 }
880 // update once at end of iteration to reduce heap write traffic
881 cursor = i;
882 lastRet = i - 1;
883 checkForComodification();
884 }
885
886 final void checkForComodification() {
887 if (modCount != expectedModCount)
888 throw new ConcurrentModificationException();
889 }
890 }
891
892 /**
893 * An optimized version of AbstractList.ListItr
894 */
895 private class ListItr extends Itr implements ListIterator<E> {
896 ListItr(int index) {
897 super();
898 cursor = index;
899 }
900
901 public boolean hasPrevious() {
902 return cursor != 0;
903 }
904
905 public int nextIndex() {
906 return cursor;
907 }
908
909 public int previousIndex() {
910 return cursor - 1;
911 }
912
913 @SuppressWarnings("unchecked")
914 public E previous() {
915 checkForComodification();
916 int i = cursor - 1;
917 if (i < 0)
918 throw new NoSuchElementException();
919 Object[] elementData = ArrayList.this.elementData;
920 if (i >= elementData.length)
921 throw new ConcurrentModificationException();
922 cursor = i;
923 return (E) elementData[lastRet = i];
924 }
925
926 public void set(E e) {
927 if (lastRet < 0)
928 throw new IllegalStateException();
929 checkForComodification();
930
931 try {
932 ArrayList.this.set(lastRet, e);
933 } catch (IndexOutOfBoundsException ex) {
934 throw new ConcurrentModificationException();
935 }
936 }
937
938 public void add(E e) {
939 checkForComodification();
940
941 try {
942 int i = cursor;
943 ArrayList.this.add(i, e);
944 cursor = i + 1;
945 lastRet = -1;
946 expectedModCount = modCount;
947 } catch (IndexOutOfBoundsException ex) {
948 throw new ConcurrentModificationException();
949 }
950 }
951 }
952
953 /**
954 * Returns a view of the portion of this list between the specified
955 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. (If
956 * {@code fromIndex} and {@code toIndex} are equal, the returned list is
957 * empty.) The returned list is backed by this list, so non-structural
958 * changes in the returned list are reflected in this list, and vice-versa.
959 * The returned list supports all of the optional list operations.
960 *
961 * <p>This method eliminates the need for explicit range operations (of
962 * the sort that commonly exist for arrays). Any operation that expects
963 * a list can be used as a range operation by passing a subList view
964 * instead of a whole list. For example, the following idiom
965 * removes a range of elements from a list:
966 * <pre>
967 * list.subList(from, to).clear();
968 * </pre>
969 * Similar idioms may be constructed for {@link #indexOf(Object)} and
970 * {@link #lastIndexOf(Object)}, and all of the algorithms in the
971 * {@link Collections} class can be applied to a subList.
972 *
973 * <p>The semantics of the list returned by this method become undefined if
974 * the backing list (i.e., this list) is <i>structurally modified</i> in
975 * any way other than via the returned list. (Structural modifications are
976 * those that change the size of this list, or otherwise perturb it in such
977 * a fashion that iterations in progress may yield incorrect results.)
978 *
979 * @throws IndexOutOfBoundsException {@inheritDoc}
980 * @throws IllegalArgumentException {@inheritDoc}
981 */
982 public List<E> subList(int fromIndex, int toIndex) {
983 subListRangeCheck(fromIndex, toIndex, size);
984 return new SubList(this, 0, fromIndex, toIndex);
985 }
986
987 static void subListRangeCheck(int fromIndex, int toIndex, int size) {
988 if (fromIndex < 0)
989 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
990 if (toIndex > size)
991 throw new IndexOutOfBoundsException("toIndex = " + toIndex);
992 if (fromIndex > toIndex)
993 throw new IllegalArgumentException("fromIndex(" + fromIndex +
994 ") > toIndex(" + toIndex + ")");
995 }
996
997 private class SubList extends AbstractList<E> implements RandomAccess {
998 private final AbstractList<E> parent;
999 private final int parentOffset;
1000 private final int offset;
1001 int size;
1002
1003 SubList(AbstractList<E> parent,
1004 int offset, int fromIndex, int toIndex) {
1005 this.parent = parent;
1006 this.parentOffset = fromIndex;
1007 this.offset = offset + fromIndex;
1008 this.size = toIndex - fromIndex;
1009 this.modCount = ArrayList.this.modCount;
1010 }
1011
1012 public E set(int index, E e) {
1013 rangeCheck(index);
1014 checkForComodification();
1015 E oldValue = ArrayList.this.elementData(offset + index);
1016 ArrayList.this.elementData[offset + index] = e;
1017 return oldValue;
1018 }
1019
1020 public E get(int index) {
1021 rangeCheck(index);
1022 checkForComodification();
1023 return ArrayList.this.elementData(offset + index);
1024 }
1025
1026 public int size() {
1027 checkForComodification();
1028 return this.size;
1029 }
1030
1031 public void add(int index, E e) {
1032 rangeCheckForAdd(index);
1033 checkForComodification();
1034 parent.add(parentOffset + index, e);
1035 this.modCount = parent.modCount;
1036 this.size++;
1037 }
1038
1039 public E remove(int index) {
1040 rangeCheck(index);
1041 checkForComodification();
1042 E result = parent.remove(parentOffset + index);
1043 this.modCount = parent.modCount;
1044 this.size--;
1045 return result;
1046 }
1047
1048 protected void removeRange(int fromIndex, int toIndex) {
1049 checkForComodification();
1050 parent.removeRange(parentOffset + fromIndex,
1051 parentOffset + toIndex);
1052 this.modCount = parent.modCount;
1053 this.size -= toIndex - fromIndex;
1054 }
1055
1056 public boolean addAll(Collection<? extends E> c) {
1057 return addAll(this.size, c);
1058 }
1059
1060 public boolean addAll(int index, Collection<? extends E> c) {
1061 rangeCheckForAdd(index);
1062 int cSize = c.size();
1063 if (cSize==0)
1064 return false;
1065
1066 checkForComodification();
1067 parent.addAll(parentOffset + index, c);
1068 this.modCount = parent.modCount;
1069 this.size += cSize;
1070 return true;
1071 }
1072
1073 public Iterator<E> iterator() {
1074 return listIterator();
1075 }
1076
1077 public ListIterator<E> listIterator(final int index) {
1078 checkForComodification();
1079 rangeCheckForAdd(index);
1080 final int offset = this.offset;
1081
1082 return new ListIterator<E>() {
1083 int cursor = index;
1084 int lastRet = -1;
1085 int expectedModCount = ArrayList.this.modCount;
1086
1087 public boolean hasNext() {
1088 return cursor != SubList.this.size;
1089 }
1090
1091 @SuppressWarnings("unchecked")
1092 public E next() {
1093 checkForComodification();
1094 int i = cursor;
1095 if (i >= SubList.this.size)
1096 throw new NoSuchElementException();
1097 Object[] elementData = ArrayList.this.elementData;
1098 if (offset + i >= elementData.length)
1099 throw new ConcurrentModificationException();
1100 cursor = i + 1;
1101 return (E) elementData[offset + (lastRet = i)];
1102 }
1103
1104 public boolean hasPrevious() {
1105 return cursor != 0;
1106 }
1107
1108 @SuppressWarnings("unchecked")
1109 public E previous() {
1110 checkForComodification();
1111 int i = cursor - 1;
1112 if (i < 0)
1113 throw new NoSuchElementException();
1114 Object[] elementData = ArrayList.this.elementData;
1115 if (offset + i >= elementData.length)
1116 throw new ConcurrentModificationException();
1117 cursor = i;
1118 return (E) elementData[offset + (lastRet = i)];
1119 }
1120
1121 @SuppressWarnings("unchecked")
1122 public void forEachRemaining(Consumer<? super E> consumer) {
1123 Objects.requireNonNull(consumer);
1124 final int size = SubList.this.size;
1125 int i = cursor;
1126 if (i >= size) {
1127 return;
1128 }
1129 final Object[] elementData = ArrayList.this.elementData;
1130 if (offset + i >= elementData.length) {
1131 throw new ConcurrentModificationException();
1132 }
1133 while (i != size && modCount == expectedModCount) {
1134 consumer.accept((E) elementData[offset + (i++)]);
1135 }
1136 // update once at end of iteration to reduce heap write traffic
1137 lastRet = cursor = i;
1138 checkForComodification();
1139 }
1140
1141 public int nextIndex() {
1142 return cursor;
1143 }
1144
1145 public int previousIndex() {
1146 return cursor - 1;
1147 }
1148
1149 public void remove() {
1150 if (lastRet < 0)
1151 throw new IllegalStateException();
1152 checkForComodification();
1153
1154 try {
1155 SubList.this.remove(lastRet);
1156 cursor = lastRet;
1157 lastRet = -1;
1158 expectedModCount = ArrayList.this.modCount;
1159 } catch (IndexOutOfBoundsException ex) {
1160 throw new ConcurrentModificationException();
1161 }
1162 }
1163
1164 public void set(E e) {
1165 if (lastRet < 0)
1166 throw new IllegalStateException();
1167 checkForComodification();
1168
1169 try {
1170 ArrayList.this.set(offset + lastRet, e);
1171 } catch (IndexOutOfBoundsException ex) {
1172 throw new ConcurrentModificationException();
1173 }
1174 }
1175
1176 public void add(E e) {
1177 checkForComodification();
1178
1179 try {
1180 int i = cursor;
1181 SubList.this.add(i, e);
1182 cursor = i + 1;
1183 lastRet = -1;
1184 expectedModCount = ArrayList.this.modCount;
1185 } catch (IndexOutOfBoundsException ex) {
1186 throw new ConcurrentModificationException();
1187 }
1188 }
1189
1190 final void checkForComodification() {
1191 if (expectedModCount != ArrayList.this.modCount)
1192 throw new ConcurrentModificationException();
1193 }
1194 };
1195 }
1196
1197 public List<E> subList(int fromIndex, int toIndex) {
1198 subListRangeCheck(fromIndex, toIndex, size);
1199 return new SubList(this, offset, fromIndex, toIndex);
1200 }
1201
1202 private void rangeCheck(int index) {
1203 if (index < 0 || index >= this.size)
1204 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
1205 }
1206
1207 private void rangeCheckForAdd(int index) {
1208 if (index < 0 || index > this.size)
1209 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
1210 }
1211
1212 private String outOfBoundsMsg(int index) {
1213 return "Index: "+index+", Size: "+this.size;
1214 }
1215
1216 private void checkForComodification() {
1217 if (ArrayList.this.modCount != this.modCount)
1218 throw new ConcurrentModificationException();
1219 }
1220
1221 public Spliterator<E> spliterator() {
1222 checkForComodification();
1223 return new ArrayListSpliterator<>(ArrayList.this, offset,
1224 offset + this.size, this.modCount);
1225 }
1226 }
1227
1228 @Override
1229 public void forEach(Consumer<? super E> action) {
1230 Objects.requireNonNull(action);
1231 final int expectedModCount = modCount;
1232 @SuppressWarnings("unchecked")
1233 final E[] elementData = (E[]) this.elementData;
1234 final int size = this.size;
1235 for (int i=0; modCount == expectedModCount && i < size; i++) {
1236 action.accept(elementData[i]);
1237 }
1238 if (modCount != expectedModCount) {
1239 throw new ConcurrentModificationException();
1240 }
1241 }
1242
1243 /**
1244 * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
1245 * and <em>fail-fast</em> {@link Spliterator} over the elements in this
1246 * list.
1247 *
1248 * <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
1249 * {@link Spliterator#SUBSIZED}, and {@link Spliterator#ORDERED}.
1250 * Overriding implementations should document the reporting of additional
1251 * characteristic values.
1252 *
1253 * @return a {@code Spliterator} over the elements in this list
1254 * @since 1.8
1255 */
1256 @Override
1257 public Spliterator<E> spliterator() {
1258 return new ArrayListSpliterator<>(this, 0, -1, 0);
1259 }
1260
1261 /** Index-based split-by-two, lazily initialized Spliterator */
1262 static final class ArrayListSpliterator<E> implements Spliterator<E> {
1263
1264 /*
1265 * If ArrayLists were immutable, or structurally immutable (no
1266 * adds, removes, etc), we could implement their spliterators
1267 * with Arrays.spliterator. Instead we detect as much
1268 * interference during traversal as practical without
1269 * sacrificing much performance. We rely primarily on
1270 * modCounts. These are not guaranteed to detect concurrency
1271 * violations, and are sometimes overly conservative about
1272 * within-thread interference, but detect enough problems to
1273 * be worthwhile in practice. To carry this out, we (1) lazily
1274 * initialize fence and expectedModCount until the latest
1275 * point that we need to commit to the state we are checking
1276 * against; thus improving precision. (This doesn't apply to
1277 * SubLists, that create spliterators with current non-lazy
1278 * values). (2) We perform only a single
1279 * ConcurrentModificationException check at the end of forEach
1280 * (the most performance-sensitive method). When using forEach
1281 * (as opposed to iterators), we can normally only detect
1282 * interference after actions, not before. Further
1283 * CME-triggering checks apply to all other possible
1284 * violations of assumptions for example null or too-small
1285 * elementData array given its size(), that could only have
1286 * occurred due to interference. This allows the inner loop
1287 * of forEach to run without any further checks, and
1288 * simplifies lambda-resolution. While this does entail a
1289 * number of checks, note that in the common case of
1290 * list.stream().forEach(a), no checks or other computation
1291 * occur anywhere other than inside forEach itself. The other
1292 * less-often-used methods cannot take advantage of most of
1293 * these streamlinings.
1294 */
1295
1296 private final ArrayList<E> list;
1297 private int index; // current index, modified on advance/split
1298 private int fence; // -1 until used; then one past last index
1299 private int expectedModCount; // initialized when fence set
1300
1301 /** Create new spliterator covering the given range */
1302 ArrayListSpliterator(ArrayList<E> list, int origin, int fence,
1303 int expectedModCount) {
1304 this.list = list; // OK if null unless traversed
1305 this.index = origin;
1306 this.fence = fence;
1307 this.expectedModCount = expectedModCount;
1308 }
1309
1310 private int getFence() { // initialize fence to size on first use
1311 int hi; // (a specialized variant appears in method forEach)
1312 ArrayList<E> lst;
1313 if ((hi = fence) < 0) {
1314 if ((lst = list) == null)
1315 hi = fence = 0;
1316 else {
1317 expectedModCount = lst.modCount;
1318 hi = fence = lst.size;
1319 }
1320 }
1321 return hi;
1322 }
1323
1324 public ArrayListSpliterator<E> trySplit() {
1325 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1326 return (lo >= mid) ? null : // divide range in half unless too small
1327 new ArrayListSpliterator<>(list, lo, index = mid,
1328 expectedModCount);
1329 }
1330
1331 public boolean tryAdvance(Consumer<? super E> action) {
1332 if (action == null)
1333 throw new NullPointerException();
1334 int hi = getFence(), i = index;
1335 if (i < hi) {
1336 index = i + 1;
1337 @SuppressWarnings("unchecked") E e = (E)list.elementData[i];
1338 action.accept(e);
1339 if (list.modCount != expectedModCount)
1340 throw new ConcurrentModificationException();
1341 return true;
1342 }
1343 return false;
1344 }
1345
1346 public void forEachRemaining(Consumer<? super E> action) {
1347 int i, hi, mc; // hoist accesses and checks from loop
1348 ArrayList<E> lst; Object[] a;
1349 if (action == null)
1350 throw new NullPointerException();
1351 if ((lst = list) != null && (a = lst.elementData) != null) {
1352 if ((hi = fence) < 0) {
1353 mc = lst.modCount;
1354 hi = lst.size;
1355 }
1356 else
1357 mc = expectedModCount;
1358 if ((i = index) >= 0 && (index = hi) <= a.length) {
1359 for (; i < hi; ++i) {
1360 @SuppressWarnings("unchecked") E e = (E) a[i];
1361 action.accept(e);
1362 }
1363 if (lst.modCount == mc)
1364 return;
1365 }
1366 }
1367 throw new ConcurrentModificationException();
1368 }
1369
1370 public long estimateSize() {
1371 return (long) (getFence() - index);
1372 }
1373
1374 public int characteristics() {
1375 return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
1376 }
1377 }
1378
1379 @Override
1380 public boolean removeIf(Predicate<? super E> filter) {
1381 Objects.requireNonNull(filter);
1382 // figure out which elements are to be removed
1383 // any exception thrown from the filter predicate at this stage
1384 // will leave the collection unmodified
1385 int removeCount = 0;
1386 final BitSet removeSet = new BitSet(size);
1387 final int expectedModCount = modCount;
1388 final int size = this.size;
1389 for (int i=0; modCount == expectedModCount && i < size; i++) {
1390 @SuppressWarnings("unchecked")
1391 final E element = (E) elementData[i];
1392 if (filter.test(element)) {
1393 removeSet.set(i);
1394 removeCount++;
1395 }
1396 }
1397 if (modCount != expectedModCount) {
1398 throw new ConcurrentModificationException();
1399 }
1400
1401 // shift surviving elements left over the spaces left by removed elements
1402 final boolean anyToRemove = removeCount > 0;
1403 if (anyToRemove) {
1404 final int newSize = size - removeCount;
1405 for (int i=0, j=0; (i < size) && (j < newSize); i++, j++) {
1406 i = removeSet.nextClearBit(i);
1407 elementData[j] = elementData[i];
1408 }
1409 for (int k=newSize; k < size; k++) {
1410 elementData[k] = null; // Let gc do its work
1411 }
1412 this.size = newSize;
1413 if (modCount != expectedModCount) {
1414 throw new ConcurrentModificationException();
1415 }
1416 modCount++;
1417 }
1418
1419 return anyToRemove;
1420 }
1421
1422 @Override
1423 @SuppressWarnings("unchecked")
1424 public void replaceAll(UnaryOperator<E> operator) {
1425 Objects.requireNonNull(operator);
1426 final int expectedModCount = modCount;
1427 final int size = this.size;
1428 for (int i=0; modCount == expectedModCount && i < size; i++) {
1429 elementData[i] = operator.apply((E) elementData[i]);
1430 }
1431 if (modCount != expectedModCount) {
1432 throw new ConcurrentModificationException();
1433 }
1434 modCount++;
1435 }
1436
1437 @Override
1438 @SuppressWarnings("unchecked")
1439 public void sort(Comparator<? super E> c) {
1440 final int expectedModCount = modCount;
1441 Arrays.sort((E[]) elementData, 0, size, c);
1442 if (modCount != expectedModCount) {
1443 throw new ConcurrentModificationException();
1444 }
1445 modCount++;
1446 }
1447 }