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>:
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 private transient Object[] elementData;
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 * fromIndex >= size() ||
613 * toIndex > size() ||
614 * toIndex < fromIndex})
615 */
616 protected void removeRange(int fromIndex, int toIndex) {
617 modCount++;
618 int numMoved = size - toIndex;
619 System.arraycopy(elementData, toIndex, elementData, fromIndex,
620 numMoved);
621
622 // clear to let GC do its work
623 int newSize = size - (toIndex-fromIndex);
624 for (int i = newSize; i < size; i++) {
625 elementData[i] = null;
626 }
627 size = newSize;
628 }
629
630 /**
631 * Checks if the given index is in range. If not, throws an appropriate
632 * runtime exception. This method does *not* check if the index is
633 * negative: It is always used immediately prior to an array access,
634 * which throws an ArrayIndexOutOfBoundsException if index is negative.
635 */
636 private void rangeCheck(int index) {
637 if (index >= size)
638 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
639 }
640
641 /**
642 * A version of rangeCheck used by add and addAll.
643 */
644 private void rangeCheckForAdd(int index) {
645 if (index > size || index < 0)
646 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
647 }
648
649 /**
650 * Constructs an IndexOutOfBoundsException detail message.
651 * Of the many possible refactorings of the error handling code,
652 * this "outlining" performs best with both server and client VMs.
653 */
654 private String outOfBoundsMsg(int index) {
655 return "Index: "+index+", Size: "+size;
656 }
657
658 /**
659 * Removes from this list all of its elements that are contained in the
660 * specified collection.
661 *
662 * @param c collection containing elements to be removed from this list
663 * @return {@code true} if this list changed as a result of the call
664 * @throws ClassCastException if the class of an element of this list
665 * is incompatible with the specified collection
666 * (<a href="Collection.html#optional-restrictions">optional</a>)
667 * @throws NullPointerException if this list contains a null element and the
668 * specified collection does not permit null elements
669 * (<a href="Collection.html#optional-restrictions">optional</a>),
670 * or if the specified collection is null
671 * @see Collection#contains(Object)
672 */
673 public boolean removeAll(Collection<?> c) {
674 return batchRemove(c, false);
675 }
676
677 /**
678 * Retains only the elements in this list that are contained in the
679 * specified collection. In other words, removes from this list all
680 * of its elements that are not contained in the specified collection.
681 *
682 * @param c collection containing elements to be retained in this list
683 * @return {@code true} if this list changed as a result of the call
684 * @throws ClassCastException if the class of an element of this list
685 * is incompatible with the specified collection
686 * (<a href="Collection.html#optional-restrictions">optional</a>)
687 * @throws NullPointerException if this list contains a null element and the
688 * specified collection does not permit null elements
689 * (<a href="Collection.html#optional-restrictions">optional</a>),
690 * or if the specified collection is null
691 * @see Collection#contains(Object)
692 */
693 public boolean retainAll(Collection<?> c) {
694 return batchRemove(c, true);
695 }
696
697 private boolean batchRemove(Collection<?> c, boolean complement) {
698 final Object[] elementData = this.elementData;
699 int r = 0, w = 0;
700 boolean modified = false;
701 try {
702 for (; r < size; r++)
703 if (c.contains(elementData[r]) == complement)
704 elementData[w++] = elementData[r];
705 } finally {
706 // Preserve behavioral compatibility with AbstractCollection,
707 // even if c.contains() throws.
708 if (r != size) {
709 System.arraycopy(elementData, r,
710 elementData, w,
711 size - r);
712 w += size - r;
713 }
714 if (w != size) {
715 // clear to let GC do its work
716 for (int i = w; i < size; i++)
717 elementData[i] = null;
718 modCount += size - w;
719 size = w;
720 modified = true;
721 }
722 }
723 return modified;
724 }
725
726 /**
727 * Save the state of the <tt>ArrayList</tt> instance to a stream (that
728 * is, serialize it).
729 *
730 * @serialData The length of the array backing the <tt>ArrayList</tt>
731 * instance is emitted (int), followed by all of its elements
732 * (each an <tt>Object</tt>) in the proper order.
733 */
734 private void writeObject(java.io.ObjectOutputStream s)
735 throws java.io.IOException{
736 // Write out element count, and any hidden stuff
737 int expectedModCount = modCount;
738 s.defaultWriteObject();
739
740 // Write out size as capacity for behavioural compatibility with clone()
741 s.writeInt(size);
742
743 // Write out all elements in the proper order.
744 for (int i=0; i<size; i++) {
745 s.writeObject(elementData[i]);
746 }
747
748 if (modCount != expectedModCount) {
749 throw new ConcurrentModificationException();
750 }
751 }
752
753 /**
754 * Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
755 * deserialize it).
756 */
757 private void readObject(java.io.ObjectInputStream s)
758 throws java.io.IOException, ClassNotFoundException {
759 elementData = EMPTY_ELEMENTDATA;
760
761 // Read in size, and any hidden stuff
762 s.defaultReadObject();
763
764 // Read in capacity
765 s.readInt(); // ignored
766
767 if (size > 0) {
768 // be like clone(), allocate array based upon size not capacity
769 ensureCapacityInternal(size);
770
771 Object[] a = elementData;
772 // Read in all elements in the proper order.
773 for (int i=0; i<size; i++) {
774 a[i] = s.readObject();
775 }
776 }
777 }
778
779 /**
780 * Returns a list iterator over the elements in this list (in proper
781 * sequence), starting at the specified position in the list.
782 * The specified index indicates the first element that would be
783 * returned by an initial call to {@link ListIterator#next next}.
784 * An initial call to {@link ListIterator#previous previous} would
785 * return the element with the specified index minus one.
786 *
787 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
788 *
789 * @throws IndexOutOfBoundsException {@inheritDoc}
790 */
791 public ListIterator<E> listIterator(int index) {
792 if (index < 0 || index > size)
793 throw new IndexOutOfBoundsException("Index: "+index);
794 return new ListItr(index);
795 }
796
797 /**
798 * Returns a list iterator over the elements in this list (in proper
799 * sequence).
800 *
801 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
802 *
803 * @see #listIterator(int)
804 */
805 public ListIterator<E> listIterator() {
806 return new ListItr(0);
807 }
808
809 /**
810 * Returns an iterator over the elements in this list in proper sequence.
811 *
812 * <p>The returned iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
813 *
814 * @return an iterator over the elements in this list in proper sequence
815 */
816 public Iterator<E> iterator() {
817 return new Itr();
818 }
819
820 /**
821 * An optimized version of AbstractList.Itr
822 */
823 private class Itr implements Iterator<E> {
824 int cursor; // index of next element to return
825 int lastRet = -1; // index of last element returned; -1 if no such
826 int expectedModCount = modCount;
827
828 public boolean hasNext() {
829 return cursor != size;
830 }
831
832 @SuppressWarnings("unchecked")
833 public E next() {
834 checkForComodification();
835 int i = cursor;
836 if (i >= size)
837 throw new NoSuchElementException();
838 Object[] elementData = ArrayList.this.elementData;
839 if (i >= elementData.length)
840 throw new ConcurrentModificationException();
841 cursor = i + 1;
842 return (E) elementData[lastRet = i];
843 }
844
845 public void remove() {
846 if (lastRet < 0)
847 throw new IllegalStateException();
848 checkForComodification();
849
850 try {
851 ArrayList.this.remove(lastRet);
852 cursor = lastRet;
853 lastRet = -1;
854 expectedModCount = modCount;
855 } catch (IndexOutOfBoundsException ex) {
856 throw new ConcurrentModificationException();
857 }
858 }
859
860 final void checkForComodification() {
861 if (modCount != expectedModCount)
862 throw new ConcurrentModificationException();
863 }
864 }
865
866 /**
867 * An optimized version of AbstractList.ListItr
868 */
869 private class ListItr extends Itr implements ListIterator<E> {
870 ListItr(int index) {
871 super();
872 cursor = index;
873 }
874
875 public boolean hasPrevious() {
876 return cursor != 0;
877 }
878
879 public int nextIndex() {
880 return cursor;
881 }
882
883 public int previousIndex() {
884 return cursor - 1;
885 }
886
887 @SuppressWarnings("unchecked")
888 public E previous() {
889 checkForComodification();
890 int i = cursor - 1;
891 if (i < 0)
892 throw new NoSuchElementException();
893 Object[] elementData = ArrayList.this.elementData;
894 if (i >= elementData.length)
895 throw new ConcurrentModificationException();
896 cursor = i;
897 return (E) elementData[lastRet = i];
898 }
899
900 public void set(E e) {
901 if (lastRet < 0)
902 throw new IllegalStateException();
903 checkForComodification();
904
905 try {
906 ArrayList.this.set(lastRet, e);
907 } catch (IndexOutOfBoundsException ex) {
908 throw new ConcurrentModificationException();
909 }
910 }
911
912 public void add(E e) {
913 checkForComodification();
914
915 try {
916 int i = cursor;
917 ArrayList.this.add(i, e);
918 cursor = i + 1;
919 lastRet = -1;
920 expectedModCount = modCount;
921 } catch (IndexOutOfBoundsException ex) {
922 throw new ConcurrentModificationException();
923 }
924 }
925 }
926
927 /**
928 * Returns a view of the portion of this list between the specified
929 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. (If
930 * {@code fromIndex} and {@code toIndex} are equal, the returned list is
931 * empty.) The returned list is backed by this list, so non-structural
932 * changes in the returned list are reflected in this list, and vice-versa.
933 * The returned list supports all of the optional list operations.
934 *
935 * <p>This method eliminates the need for explicit range operations (of
936 * the sort that commonly exist for arrays). Any operation that expects
937 * a list can be used as a range operation by passing a subList view
938 * instead of a whole list. For example, the following idiom
939 * removes a range of elements from a list:
940 * <pre>
941 * list.subList(from, to).clear();
942 * </pre>
943 * Similar idioms may be constructed for {@link #indexOf(Object)} and
944 * {@link #lastIndexOf(Object)}, and all of the algorithms in the
945 * {@link Collections} class can be applied to a subList.
946 *
947 * <p>The semantics of the list returned by this method become undefined if
948 * the backing list (i.e., this list) is <i>structurally modified</i> in
949 * any way other than via the returned list. (Structural modifications are
950 * those that change the size of this list, or otherwise perturb it in such
951 * a fashion that iterations in progress may yield incorrect results.)
952 *
953 * @throws IndexOutOfBoundsException {@inheritDoc}
954 * @throws IllegalArgumentException {@inheritDoc}
955 */
956 public List<E> subList(int fromIndex, int toIndex) {
957 subListRangeCheck(fromIndex, toIndex, size);
958 return new SubList(this, 0, fromIndex, toIndex);
959 }
960
961 static void subListRangeCheck(int fromIndex, int toIndex, int size) {
962 if (fromIndex < 0)
963 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
964 if (toIndex > size)
965 throw new IndexOutOfBoundsException("toIndex = " + toIndex);
966 if (fromIndex > toIndex)
967 throw new IllegalArgumentException("fromIndex(" + fromIndex +
968 ") > toIndex(" + toIndex + ")");
969 }
970
971 private class SubList extends AbstractList<E> implements RandomAccess {
972 private final AbstractList<E> parent;
973 private final int parentOffset;
974 private final int offset;
975 int size;
976
977 SubList(AbstractList<E> parent,
978 int offset, int fromIndex, int toIndex) {
979 this.parent = parent;
980 this.parentOffset = fromIndex;
981 this.offset = offset + fromIndex;
982 this.size = toIndex - fromIndex;
983 this.modCount = ArrayList.this.modCount;
984 }
985
986 public E set(int index, E e) {
987 rangeCheck(index);
988 checkForComodification();
989 E oldValue = ArrayList.this.elementData(offset + index);
990 ArrayList.this.elementData[offset + index] = e;
991 return oldValue;
992 }
993
994 public E get(int index) {
995 rangeCheck(index);
996 checkForComodification();
997 return ArrayList.this.elementData(offset + index);
998 }
999
1000 public int size() {
1001 checkForComodification();
1002 return this.size;
1003 }
1004
1005 public void add(int index, E e) {
1006 rangeCheckForAdd(index);
1007 checkForComodification();
1008 parent.add(parentOffset + index, e);
1009 this.modCount = parent.modCount;
1010 this.size++;
1011 }
1012
1013 public E remove(int index) {
1014 rangeCheck(index);
1015 checkForComodification();
1016 E result = parent.remove(parentOffset + index);
1017 this.modCount = parent.modCount;
1018 this.size--;
1019 return result;
1020 }
1021
1022 protected void removeRange(int fromIndex, int toIndex) {
1023 checkForComodification();
1024 parent.removeRange(parentOffset + fromIndex,
1025 parentOffset + toIndex);
1026 this.modCount = parent.modCount;
1027 this.size -= toIndex - fromIndex;
1028 }
1029
1030 public boolean addAll(Collection<? extends E> c) {
1031 return addAll(this.size, c);
1032 }
1033
1034 public boolean addAll(int index, Collection<? extends E> c) {
1035 rangeCheckForAdd(index);
1036 int cSize = c.size();
1037 if (cSize==0)
1038 return false;
1039
1040 checkForComodification();
1041 parent.addAll(parentOffset + index, c);
1042 this.modCount = parent.modCount;
1043 this.size += cSize;
1044 return true;
1045 }
1046
1047 public Iterator<E> iterator() {
1048 return listIterator();
1049 }
1050
1051 public ListIterator<E> listIterator(final int index) {
1052 checkForComodification();
1053 rangeCheckForAdd(index);
1054 final int offset = this.offset;
1055
1056 return new ListIterator<E>() {
1057 int cursor = index;
1058 int lastRet = -1;
1059 int expectedModCount = ArrayList.this.modCount;
1060
1061 public boolean hasNext() {
1062 return cursor != SubList.this.size;
1063 }
1064
1065 @SuppressWarnings("unchecked")
1066 public E next() {
1067 checkForComodification();
1068 int i = cursor;
1069 if (i >= SubList.this.size)
1070 throw new NoSuchElementException();
1071 Object[] elementData = ArrayList.this.elementData;
1072 if (offset + i >= elementData.length)
1073 throw new ConcurrentModificationException();
1074 cursor = i + 1;
1075 return (E) elementData[offset + (lastRet = i)];
1076 }
1077
1078 public boolean hasPrevious() {
1079 return cursor != 0;
1080 }
1081
1082 @SuppressWarnings("unchecked")
1083 public E previous() {
1084 checkForComodification();
1085 int i = cursor - 1;
1086 if (i < 0)
1087 throw new NoSuchElementException();
1088 Object[] elementData = ArrayList.this.elementData;
1089 if (offset + i >= elementData.length)
1090 throw new ConcurrentModificationException();
1091 cursor = i;
1092 return (E) elementData[offset + (lastRet = i)];
1093 }
1094
1095 public int nextIndex() {
1096 return cursor;
1097 }
1098
1099 public int previousIndex() {
1100 return cursor - 1;
1101 }
1102
1103 public void remove() {
1104 if (lastRet < 0)
1105 throw new IllegalStateException();
1106 checkForComodification();
1107
1108 try {
1109 SubList.this.remove(lastRet);
1110 cursor = lastRet;
1111 lastRet = -1;
1112 expectedModCount = ArrayList.this.modCount;
1113 } catch (IndexOutOfBoundsException ex) {
1114 throw new ConcurrentModificationException();
1115 }
1116 }
1117
1118 public void set(E e) {
1119 if (lastRet < 0)
1120 throw new IllegalStateException();
1121 checkForComodification();
1122
1123 try {
1124 ArrayList.this.set(offset + lastRet, e);
1125 } catch (IndexOutOfBoundsException ex) {
1126 throw new ConcurrentModificationException();
1127 }
1128 }
1129
1130 public void add(E e) {
1131 checkForComodification();
1132
1133 try {
1134 int i = cursor;
1135 SubList.this.add(i, e);
1136 cursor = i + 1;
1137 lastRet = -1;
1138 expectedModCount = ArrayList.this.modCount;
1139 } catch (IndexOutOfBoundsException ex) {
1140 throw new ConcurrentModificationException();
1141 }
1142 }
1143
1144 final void checkForComodification() {
1145 if (expectedModCount != ArrayList.this.modCount)
1146 throw new ConcurrentModificationException();
1147 }
1148 };
1149 }
1150
1151 public List<E> subList(int fromIndex, int toIndex) {
1152 subListRangeCheck(fromIndex, toIndex, size);
1153 return new SubList(this, offset, fromIndex, toIndex);
1154 }
1155
1156 private void rangeCheck(int index) {
1157 if (index < 0 || index >= this.size)
1158 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
1159 }
1160
1161 private void rangeCheckForAdd(int index) {
1162 if (index < 0 || index > this.size)
1163 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
1164 }
1165
1166 private String outOfBoundsMsg(int index) {
1167 return "Index: "+index+", Size: "+this.size;
1168 }
1169
1170 private void checkForComodification() {
1171 if (ArrayList.this.modCount != this.modCount)
1172 throw new ConcurrentModificationException();
1173 }
1174 }
1175
1176 @Override
1177 public void forEach(Consumer<? super E> action) {
1178 Objects.requireNonNull(action);
1179 final int expectedModCount = modCount;
1180 @SuppressWarnings("unchecked")
1181 final E[] elementData = (E[]) this.elementData;
1182 final int size = this.size;
1183 for (int i=0; modCount == expectedModCount && i < size; i++) {
1184 action.accept(elementData[i]);
1185 }
1186 if (modCount != expectedModCount) {
1187 throw new ConcurrentModificationException();
1188 }
1189 }
1190
1191 @Override
1192 public boolean removeIf(Predicate<? super E> filter) {
1193 Objects.requireNonNull(filter);
1194 // figure out which elements are to be removed
1195 // any exception thrown from the filter predicate at this stage
1196 // will leave the collection unmodified
1197 int removeCount = 0;
1198 final BitSet removeSet = new BitSet(size);
1199 final int expectedModCount = modCount;
1200 final int size = this.size;
1201 for (int i=0; modCount == expectedModCount && i < size; i++) {
1202 @SuppressWarnings("unchecked")
1203 final E element = (E) elementData[i];
1204 if (filter.test(element)) {
1205 removeSet.set(i);
1206 removeCount++;
1207 }
1208 }
1209 if (modCount != expectedModCount) {
1210 throw new ConcurrentModificationException();
1211 }
1212
1213 // shift surviving elements left over the spaces left by removed elements
1214 final boolean anyToRemove = removeCount > 0;
1215 if (anyToRemove) {
1216 final int newSize = size - removeCount;
1217 for (int i=0, j=0; (i < size) && (j < newSize); i++, j++) {
1218 i = removeSet.nextClearBit(i);
1219 elementData[j] = elementData[i];
1220 }
1221 for (int k=newSize; k < size; k++) {
1222 elementData[k] = null; // Let gc do its work
1223 }
1224 this.size = newSize;
1225 if (modCount != expectedModCount) {
1226 throw new ConcurrentModificationException();
1227 }
1228 modCount++;
1229 }
1230
1231 return anyToRemove;
1232 }
1233
1234 @Override
1235 @SuppressWarnings("unchecked")
1236 public void replaceAll(UnaryOperator<E> operator) {
1237 Objects.requireNonNull(operator);
1238 final int expectedModCount = modCount;
1239 final int size = this.size;
1240 for (int i=0; modCount == expectedModCount && i < size; i++) {
1241 elementData[i] = operator.apply((E) elementData[i]);
1242 }
1243 if (modCount != expectedModCount) {
1244 throw new ConcurrentModificationException();
1245 }
1246 modCount++;
1247 }
1248
1249 @Override
1250 @SuppressWarnings("unchecked")
1251 public void sort(Comparator<? super E> c) {
1252 final int expectedModCount = modCount;
1253 Arrays.sort((E[]) elementData, 0, size, c);
1254 if (modCount != expectedModCount) {
1255 throw new ConcurrentModificationException();
1256 }
1257 modCount++;
1258 }
1259 }