1 /*
2 * Copyright (c) 1997, 2012, 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.Block;
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 * The array buffer into which the elements of the ArrayList are stored.
113 * The capacity of the ArrayList is the length of this array buffer.
114 */
115 private transient Object[] elementData;
116
117 /**
118 * The size of the ArrayList (the number of elements it contains).
119 *
120 * @serial
121 */
122 private int size;
123
124 /**
125 * Constructs an empty list with the specified initial capacity.
126 *
127 * @param initialCapacity the initial capacity of the list
128 * @throws IllegalArgumentException if the specified initial capacity
129 * is negative
130 */
131 public ArrayList(int initialCapacity) {
132 super();
133 if (initialCapacity < 0)
134 throw new IllegalArgumentException("Illegal Capacity: "+
135 initialCapacity);
136 this.elementData = new Object[initialCapacity];
137 }
138
139 /**
140 * Constructs an empty list with an initial capacity of ten.
141 */
142 public ArrayList() {
143 this(10);
144 }
145
146 /**
147 * Constructs a list containing the elements of the specified
148 * collection, in the order they are returned by the collection's
149 * iterator.
150 *
151 * @param c the collection whose elements are to be placed into this list
152 * @throws NullPointerException if the specified collection is null
153 */
154 public ArrayList(Collection<? extends E> c) {
155 elementData = c.toArray();
156 size = elementData.length;
157 // c.toArray might (incorrectly) not return Object[] (see 6260652)
158 if (elementData.getClass() != Object[].class)
159 elementData = Arrays.copyOf(elementData, size, Object[].class);
160 }
161
162 /**
163 * Trims the capacity of this <tt>ArrayList</tt> instance to be the
164 * list's current size. An application can use this operation to minimize
165 * the storage of an <tt>ArrayList</tt> instance.
166 */
167 public void trimToSize() {
168 modCount++;
169 int oldCapacity = elementData.length;
170 if (size < oldCapacity) {
171 elementData = Arrays.copyOf(elementData, size);
172 }
173 }
174
175 /**
176 * Increases the capacity of this <tt>ArrayList</tt> instance, if
177 * necessary, to ensure that it can hold at least the number of elements
178 * specified by the minimum capacity argument.
179 *
180 * @param minCapacity the desired minimum capacity
181 */
182 public void ensureCapacity(int minCapacity) {
183 if (minCapacity > 0)
184 ensureCapacityInternal(minCapacity);
185 }
186
187 private void ensureCapacityInternal(int minCapacity) {
188 modCount++;
189 // overflow-conscious code
190 if (minCapacity - elementData.length > 0)
191 grow(minCapacity);
192 }
193
194 /**
195 * The maximum size of array to allocate.
196 * Some VMs reserve some header words in an array.
197 * Attempts to allocate larger arrays may result in
198 * OutOfMemoryError: Requested array size exceeds VM limit
199 */
200 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
201
202 /**
203 * Increases the capacity to ensure that it can hold at least the
204 * number of elements specified by the minimum capacity argument.
205 *
206 * @param minCapacity the desired minimum capacity
207 */
208 private void grow(int minCapacity) {
209 // overflow-conscious code
210 int oldCapacity = elementData.length;
211 int newCapacity = oldCapacity + (oldCapacity >> 1);
212 if (newCapacity - minCapacity < 0)
213 newCapacity = minCapacity;
214 if (newCapacity - MAX_ARRAY_SIZE > 0)
215 newCapacity = hugeCapacity(minCapacity);
216 // minCapacity is usually close to size, so this is a win:
217 elementData = Arrays.copyOf(elementData, newCapacity);
218 }
219
220 private static int hugeCapacity(int minCapacity) {
221 if (minCapacity < 0) // overflow
222 throw new OutOfMemoryError();
223 return (minCapacity > MAX_ARRAY_SIZE) ?
224 Integer.MAX_VALUE :
225 MAX_ARRAY_SIZE;
226 }
227
228 /**
229 * Returns the number of elements in this list.
230 *
231 * @return the number of elements in this list
232 */
233 public int size() {
234 return size;
235 }
236
237 /**
238 * Returns <tt>true</tt> if this list contains no elements.
239 *
240 * @return <tt>true</tt> if this list contains no elements
241 */
242 public boolean isEmpty() {
243 return size == 0;
244 }
245
246 /**
247 * Returns <tt>true</tt> if this list contains the specified element.
248 * More formally, returns <tt>true</tt> if and only if this list contains
249 * at least one element <tt>e</tt> such that
250 * <tt>(o==null ? e==null : o.equals(e))</tt>.
251 *
252 * @param o element whose presence in this list is to be tested
253 * @return <tt>true</tt> if this list contains the specified element
254 */
255 public boolean contains(Object o) {
256 return indexOf(o) >= 0;
257 }
258
259 /**
260 * Returns the index of the first occurrence of the specified element
261 * in this list, or -1 if this list does not contain the element.
262 * More formally, returns the lowest index <tt>i</tt> such that
263 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
264 * or -1 if there is no such index.
265 */
266 public int indexOf(Object o) {
267 if (o == null) {
268 for (int i = 0; i < size; i++)
269 if (elementData[i]==null)
270 return i;
271 } else {
272 for (int i = 0; i < size; i++)
273 if (o.equals(elementData[i]))
274 return i;
275 }
276 return -1;
277 }
278
279 /**
280 * Returns the index of the last occurrence of the specified element
281 * in this list, or -1 if this list does not contain the element.
282 * More formally, returns the highest index <tt>i</tt> such that
283 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
284 * or -1 if there is no such index.
285 */
286 public int lastIndexOf(Object o) {
287 if (o == null) {
288 for (int i = size-1; i >= 0; i--)
289 if (elementData[i]==null)
290 return i;
291 } else {
292 for (int i = size-1; i >= 0; i--)
293 if (o.equals(elementData[i]))
294 return i;
295 }
296 return -1;
297 }
298
299 /**
300 * Returns a shallow copy of this <tt>ArrayList</tt> instance. (The
301 * elements themselves are not copied.)
302 *
303 * @return a clone of this <tt>ArrayList</tt> instance
304 */
305 public Object clone() {
306 try {
307 ArrayList<?> v = (ArrayList<?>) super.clone();
308 v.elementData = Arrays.copyOf(elementData, size);
309 v.modCount = 0;
310 return v;
311 } catch (CloneNotSupportedException e) {
312 // this shouldn't happen, since we are Cloneable
313 throw new InternalError(e);
314 }
315 }
316
317 /**
318 * Returns an array containing all of the elements in this list
319 * in proper sequence (from first to last element).
320 *
321 * <p>The returned array will be "safe" in that no references to it are
322 * maintained by this list. (In other words, this method must allocate
323 * a new array). The caller is thus free to modify the returned array.
324 *
325 * <p>This method acts as bridge between array-based and collection-based
326 * APIs.
327 *
328 * @return an array containing all of the elements in this list in
329 * proper sequence
330 */
331 public Object[] toArray() {
332 return Arrays.copyOf(elementData, size);
333 }
334
335 /**
336 * Returns an array containing all of the elements in this list in proper
337 * sequence (from first to last element); the runtime type of the returned
338 * array is that of the specified array. If the list fits in the
339 * specified array, it is returned therein. Otherwise, a new array is
340 * allocated with the runtime type of the specified array and the size of
341 * this list.
342 *
343 * <p>If the list fits in the specified array with room to spare
344 * (i.e., the array has more elements than the list), the element in
345 * the array immediately following the end of the collection is set to
346 * <tt>null</tt>. (This is useful in determining the length of the
347 * list <i>only</i> if the caller knows that the list does not contain
348 * any null elements.)
349 *
350 * @param a the array into which the elements of the list are to
351 * be stored, if it is big enough; otherwise, a new array of the
352 * same runtime type is allocated for this purpose.
353 * @return an array containing the elements of the list
354 * @throws ArrayStoreException if the runtime type of the specified array
355 * is not a supertype of the runtime type of every element in
356 * this list
357 * @throws NullPointerException if the specified array is null
358 */
359 @SuppressWarnings("unchecked")
360 public <T> T[] toArray(T[] a) {
361 if (a.length < size)
362 // Make a new array of a's runtime type, but my contents:
363 return (T[]) Arrays.copyOf(elementData, size, a.getClass());
364 System.arraycopy(elementData, 0, a, 0, size);
365 if (a.length > size)
366 a[size] = null;
367 return a;
368 }
369
370 // Positional Access Operations
371
372 @SuppressWarnings("unchecked")
373 E elementData(int index) {
374 return (E) elementData[index];
375 }
376
377 /**
378 * Returns the element at the specified position in this list.
379 *
380 * @param index index of the element to return
381 * @return the element at the specified position in this list
382 * @throws IndexOutOfBoundsException {@inheritDoc}
383 */
384 public E get(int index) {
385 rangeCheck(index);
386
387 return elementData(index);
388 }
389
390 /**
391 * Replaces the element at the specified position in this list with
392 * the specified element.
393 *
394 * @param index index of the element to replace
395 * @param element element to be stored at the specified position
396 * @return the element previously at the specified position
397 * @throws IndexOutOfBoundsException {@inheritDoc}
398 */
399 public E set(int index, E element) {
400 rangeCheck(index);
401
402 E oldValue = elementData(index);
403 elementData[index] = element;
404 return oldValue;
405 }
406
407 /**
408 * Appends the specified element to the end of this list.
409 *
410 * @param e element to be appended to this list
411 * @return <tt>true</tt> (as specified by {@link Collection#add})
412 */
413 public boolean add(E e) {
414 ensureCapacityInternal(size + 1); // Increments modCount!!
415 elementData[size++] = e;
416 return true;
417 }
418
419 /**
420 * Inserts the specified element at the specified position in this
421 * list. Shifts the element currently at that position (if any) and
422 * any subsequent elements to the right (adds one to their indices).
423 *
424 * @param index index at which the specified element is to be inserted
425 * @param element element to be inserted
426 * @throws IndexOutOfBoundsException {@inheritDoc}
427 */
428 public void add(int index, E element) {
429 rangeCheckForAdd(index);
430
431 ensureCapacityInternal(size + 1); // Increments modCount!!
432 System.arraycopy(elementData, index, elementData, index + 1,
433 size - index);
434 elementData[index] = element;
435 size++;
436 }
437
438 /**
439 * Removes the element at the specified position in this list.
440 * Shifts any subsequent elements to the left (subtracts one from their
441 * indices).
442 *
443 * @param index the index of the element to be removed
444 * @return the element that was removed from the list
445 * @throws IndexOutOfBoundsException {@inheritDoc}
446 */
447 public E remove(int index) {
448 rangeCheck(index);
449
450 modCount++;
451 E oldValue = elementData(index);
452
453 int numMoved = size - index - 1;
454 if (numMoved > 0)
455 System.arraycopy(elementData, index+1, elementData, index,
456 numMoved);
457 elementData[--size] = null; // Let gc do its work
458
459 return oldValue;
460 }
461
462 /**
463 * Removes the first occurrence of the specified element from this list,
464 * if it is present. If the list does not contain the element, it is
465 * unchanged. More formally, removes the element with the lowest index
466 * <tt>i</tt> such that
467 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>
468 * (if such an element exists). Returns <tt>true</tt> if this list
469 * contained the specified element (or equivalently, if this list
470 * changed as a result of the call).
471 *
472 * @param o element to be removed from this list, if present
473 * @return <tt>true</tt> if this list contained the specified element
474 */
475 public boolean remove(Object o) {
476 if (o == null) {
477 for (int index = 0; index < size; index++)
478 if (elementData[index] == null) {
479 fastRemove(index);
480 return true;
481 }
482 } else {
483 for (int index = 0; index < size; index++)
484 if (o.equals(elementData[index])) {
485 fastRemove(index);
486 return true;
487 }
488 }
489 return false;
490 }
491
492 /*
493 * Private remove method that skips bounds checking and does not
494 * return the value removed.
495 */
496 private void fastRemove(int index) {
497 modCount++;
498 int numMoved = size - index - 1;
499 if (numMoved > 0)
500 System.arraycopy(elementData, index+1, elementData, index,
501 numMoved);
502 elementData[--size] = null; // Let gc do its work
503 }
504
505 /**
506 * Removes all of the elements from this list. The list will
507 * be empty after this call returns.
508 */
509 public void clear() {
510 modCount++;
511
512 // Let gc do its work
513 for (int i = 0; i < size; i++)
514 elementData[i] = null;
515
516 size = 0;
517 }
518
519 /**
520 * Appends all of the elements in the specified collection to the end of
521 * this list, in the order that they are returned by the
522 * specified collection's Iterator. The behavior of this operation is
523 * undefined if the specified collection is modified while the operation
524 * is in progress. (This implies that the behavior of this call is
525 * undefined if the specified collection is this list, and this
526 * list is nonempty.)
527 *
528 * @param c collection containing elements to be added to this list
529 * @return <tt>true</tt> if this list changed as a result of the call
530 * @throws NullPointerException if the specified collection is null
531 */
532 public boolean addAll(Collection<? extends E> c) {
533 Object[] a = c.toArray();
534 int numNew = a.length;
535 ensureCapacityInternal(size + numNew); // Increments modCount
536 System.arraycopy(a, 0, elementData, size, numNew);
537 size += numNew;
538 return numNew != 0;
539 }
540
541 /**
542 * Inserts all of the elements in the specified collection into this
543 * list, starting at the specified position. Shifts the element
544 * currently at that position (if any) and any subsequent elements to
545 * the right (increases their indices). The new elements will appear
546 * in the list in the order that they are returned by the
547 * specified collection's iterator.
548 *
549 * @param index index at which to insert the first element from the
550 * specified collection
551 * @param c collection containing elements to be added to this list
552 * @return <tt>true</tt> if this list changed as a result of the call
553 * @throws IndexOutOfBoundsException {@inheritDoc}
554 * @throws NullPointerException if the specified collection is null
555 */
556 public boolean addAll(int index, Collection<? extends E> c) {
557 rangeCheckForAdd(index);
558
559 Object[] a = c.toArray();
560 int numNew = a.length;
561 ensureCapacityInternal(size + numNew); // Increments modCount
562
563 int numMoved = size - index;
564 if (numMoved > 0)
565 System.arraycopy(elementData, index, elementData, index + numNew,
566 numMoved);
567
568 System.arraycopy(a, 0, elementData, index, numNew);
569 size += numNew;
570 return numNew != 0;
571 }
572
573 /**
574 * Removes from this list all of the elements whose index is between
575 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
576 * Shifts any succeeding elements to the left (reduces their index).
577 * This call shortens the list by {@code (toIndex - fromIndex)} elements.
578 * (If {@code toIndex==fromIndex}, this operation has no effect.)
579 *
580 * @throws IndexOutOfBoundsException if {@code fromIndex} or
581 * {@code toIndex} is out of range
582 * ({@code fromIndex < 0 ||
583 * fromIndex >= size() ||
584 * toIndex > size() ||
585 * toIndex < fromIndex})
586 */
587 protected void removeRange(int fromIndex, int toIndex) {
588 modCount++;
589 int numMoved = size - toIndex;
590 System.arraycopy(elementData, toIndex, elementData, fromIndex,
591 numMoved);
592
593 // Let gc do its work
594 int newSize = size - (toIndex-fromIndex);
595 while (size != newSize)
596 elementData[--size] = null;
597 }
598
599 /**
600 * Checks if the given index is in range. If not, throws an appropriate
601 * runtime exception. This method does *not* check if the index is
602 * negative: It is always used immediately prior to an array access,
603 * which throws an ArrayIndexOutOfBoundsException if index is negative.
604 */
605 private void rangeCheck(int index) {
606 if (index >= size)
607 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
608 }
609
610 /**
611 * A version of rangeCheck used by add and addAll.
612 */
613 private void rangeCheckForAdd(int index) {
614 if (index > size || index < 0)
615 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
616 }
617
618 /**
619 * Constructs an IndexOutOfBoundsException detail message.
620 * Of the many possible refactorings of the error handling code,
621 * this "outlining" performs best with both server and client VMs.
622 */
623 private String outOfBoundsMsg(int index) {
624 return "Index: "+index+", Size: "+size;
625 }
626
627 /**
628 * Removes from this list all of its elements that are contained in the
629 * specified collection.
630 *
631 * @param c collection containing elements to be removed from this list
632 * @return {@code true} if this list changed as a result of the call
633 * @throws ClassCastException if the class of an element of this list
634 * is incompatible with the specified collection
635 * (<a href="Collection.html#optional-restrictions">optional</a>)
636 * @throws NullPointerException if this list contains a null element and the
637 * specified collection does not permit null elements
638 * (<a href="Collection.html#optional-restrictions">optional</a>),
639 * or if the specified collection is null
640 * @see Collection#contains(Object)
641 */
642 public boolean removeAll(Collection<?> c) {
643 return batchRemove(c, false);
644 }
645
646 /**
647 * Retains only the elements in this list that are contained in the
648 * specified collection. In other words, removes from this list all
649 * of its elements that are not contained in the specified collection.
650 *
651 * @param c collection containing elements to be retained in this list
652 * @return {@code true} if this list changed as a result of the call
653 * @throws ClassCastException if the class of an element of this list
654 * is incompatible with the specified collection
655 * (<a href="Collection.html#optional-restrictions">optional</a>)
656 * @throws NullPointerException if this list contains a null element and the
657 * specified collection does not permit null elements
658 * (<a href="Collection.html#optional-restrictions">optional</a>),
659 * or if the specified collection is null
660 * @see Collection#contains(Object)
661 */
662 public boolean retainAll(Collection<?> c) {
663 return batchRemove(c, true);
664 }
665
666 private boolean batchRemove(Collection<?> c, boolean complement) {
667 final Object[] elementData = this.elementData;
668 int r = 0, w = 0;
669 boolean modified = false;
670 try {
671 for (; r < size; r++)
672 if (c.contains(elementData[r]) == complement)
673 elementData[w++] = elementData[r];
674 } finally {
675 // Preserve behavioral compatibility with AbstractCollection,
676 // even if c.contains() throws.
677 if (r != size) {
678 System.arraycopy(elementData, r,
679 elementData, w,
680 size - r);
681 w += size - r;
682 }
683 if (w != size) {
684 for (int i = w; i < size; i++)
685 elementData[i] = null;
686 modCount += size - w;
687 size = w;
688 modified = true;
689 }
690 }
691 return modified;
692 }
693
694 /**
695 * Save the state of the <tt>ArrayList</tt> instance to a stream (that
696 * is, serialize it).
697 *
698 * @serialData The length of the array backing the <tt>ArrayList</tt>
699 * instance is emitted (int), followed by all of its elements
700 * (each an <tt>Object</tt>) in the proper order.
701 */
702 private void writeObject(java.io.ObjectOutputStream s)
703 throws java.io.IOException{
704 // Write out element count, and any hidden stuff
705 int expectedModCount = modCount;
706 s.defaultWriteObject();
707
708 // Write out array length
709 s.writeInt(elementData.length);
710
711 // Write out all elements in the proper order.
712 for (int i=0; i<size; i++)
713 s.writeObject(elementData[i]);
714
715 if (modCount != expectedModCount) {
716 throw new ConcurrentModificationException();
717 }
718
719 }
720
721 /**
722 * Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
723 * deserialize it).
724 */
725 private void readObject(java.io.ObjectInputStream s)
726 throws java.io.IOException, ClassNotFoundException {
727 // Read in size, and any hidden stuff
728 s.defaultReadObject();
729
730 // Read in array length and allocate array
731 int arrayLength = s.readInt();
732 Object[] a = elementData = new Object[arrayLength];
733
734 // Read in all elements in the proper order.
735 for (int i=0; i<size; i++)
736 a[i] = s.readObject();
737 }
738
739 /**
740 * Returns a list iterator over the elements in this list (in proper
741 * sequence), starting at the specified position in the list.
742 * The specified index indicates the first element that would be
743 * returned by an initial call to {@link ListIterator#next next}.
744 * An initial call to {@link ListIterator#previous previous} would
745 * return the element with the specified index minus one.
746 *
747 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
748 *
749 * @throws IndexOutOfBoundsException {@inheritDoc}
750 */
751 public ListIterator<E> listIterator(int index) {
752 if (index < 0 || index > size)
753 throw new IndexOutOfBoundsException("Index: "+index);
754 return new ListItr(index);
755 }
756
757 /**
758 * Returns a list iterator over the elements in this list (in proper
759 * sequence).
760 *
761 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
762 *
763 * @see #listIterator(int)
764 */
765 public ListIterator<E> listIterator() {
766 return new ListItr(0);
767 }
768
769 /**
770 * Returns an iterator over the elements in this list in proper sequence.
771 *
772 * <p>The returned iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
773 *
774 * @return an iterator over the elements in this list in proper sequence
775 */
776 public Iterator<E> iterator() {
777 return new Itr();
778 }
779
780 /**
781 * An optimized version of AbstractList.Itr
782 */
783 private class Itr implements Iterator<E> {
784 int cursor; // index of next element to return
785 int lastRet = -1; // index of last element returned; -1 if no such
786 int expectedModCount = modCount;
787
788 public boolean hasNext() {
789 return cursor != size;
790 }
791
792 @SuppressWarnings("unchecked")
793 public E next() {
794 checkForComodification();
795 int i = cursor;
796 if (i >= size)
797 throw new NoSuchElementException();
798 Object[] elementData = ArrayList.this.elementData;
799 if (i >= elementData.length)
800 throw new ConcurrentModificationException();
801 cursor = i + 1;
802 return (E) elementData[lastRet = i];
803 }
804
805 public void remove() {
806 if (lastRet < 0)
807 throw new IllegalStateException();
808 checkForComodification();
809
810 try {
811 ArrayList.this.remove(lastRet);
812 cursor = lastRet;
813 lastRet = -1;
814 expectedModCount = modCount;
815 } catch (IndexOutOfBoundsException ex) {
816 throw new ConcurrentModificationException();
817 }
818 }
819
820 final void checkForComodification() {
821 if (modCount != expectedModCount)
822 throw new ConcurrentModificationException();
823 }
824 }
825
826 /**
827 * An optimized version of AbstractList.ListItr
828 */
829 private class ListItr extends Itr implements ListIterator<E> {
830 ListItr(int index) {
831 super();
832 cursor = index;
833 }
834
835 public boolean hasPrevious() {
836 return cursor != 0;
837 }
838
839 public int nextIndex() {
840 return cursor;
841 }
842
843 public int previousIndex() {
844 return cursor - 1;
845 }
846
847 @SuppressWarnings("unchecked")
848 public E previous() {
849 checkForComodification();
850 int i = cursor - 1;
851 if (i < 0)
852 throw new NoSuchElementException();
853 Object[] elementData = ArrayList.this.elementData;
854 if (i >= elementData.length)
855 throw new ConcurrentModificationException();
856 cursor = i;
857 return (E) elementData[lastRet = i];
858 }
859
860 public void set(E e) {
861 if (lastRet < 0)
862 throw new IllegalStateException();
863 checkForComodification();
864
865 try {
866 ArrayList.this.set(lastRet, e);
867 } catch (IndexOutOfBoundsException ex) {
868 throw new ConcurrentModificationException();
869 }
870 }
871
872 public void add(E e) {
873 checkForComodification();
874
875 try {
876 int i = cursor;
877 ArrayList.this.add(i, e);
878 cursor = i + 1;
879 lastRet = -1;
880 expectedModCount = modCount;
881 } catch (IndexOutOfBoundsException ex) {
882 throw new ConcurrentModificationException();
883 }
884 }
885 }
886
887 /**
888 * Returns a view of the portion of this list between the specified
889 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. (If
890 * {@code fromIndex} and {@code toIndex} are equal, the returned list is
891 * empty.) The returned list is backed by this list, so non-structural
892 * changes in the returned list are reflected in this list, and vice-versa.
893 * The returned list supports all of the optional list operations.
894 *
895 * <p>This method eliminates the need for explicit range operations (of
896 * the sort that commonly exist for arrays). Any operation that expects
897 * a list can be used as a range operation by passing a subList view
898 * instead of a whole list. For example, the following idiom
899 * removes a range of elements from a list:
900 * <pre>
901 * list.subList(from, to).clear();
902 * </pre>
903 * Similar idioms may be constructed for {@link #indexOf(Object)} and
904 * {@link #lastIndexOf(Object)}, and all of the algorithms in the
905 * {@link Collections} class can be applied to a subList.
906 *
907 * <p>The semantics of the list returned by this method become undefined if
908 * the backing list (i.e., this list) is <i>structurally modified</i> in
909 * any way other than via the returned list. (Structural modifications are
910 * those that change the size of this list, or otherwise perturb it in such
911 * a fashion that iterations in progress may yield incorrect results.)
912 *
913 * @throws IndexOutOfBoundsException {@inheritDoc}
914 * @throws IllegalArgumentException {@inheritDoc}
915 */
916 public List<E> subList(int fromIndex, int toIndex) {
917 subListRangeCheck(fromIndex, toIndex, size);
918 return new SubList(this, 0, fromIndex, toIndex);
919 }
920
921 static void subListRangeCheck(int fromIndex, int toIndex, int size) {
922 if (fromIndex < 0)
923 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
924 if (toIndex > size)
925 throw new IndexOutOfBoundsException("toIndex = " + toIndex);
926 if (fromIndex > toIndex)
927 throw new IllegalArgumentException("fromIndex(" + fromIndex +
928 ") > toIndex(" + toIndex + ")");
929 }
930
931 private class SubList extends AbstractList<E> implements RandomAccess {
932 private final AbstractList<E> parent;
933 private final int parentOffset;
934 private final int offset;
935 int size;
936
937 SubList(AbstractList<E> parent,
938 int offset, int fromIndex, int toIndex) {
939 this.parent = parent;
940 this.parentOffset = fromIndex;
941 this.offset = offset + fromIndex;
942 this.size = toIndex - fromIndex;
943 this.modCount = ArrayList.this.modCount;
944 }
945
946 public E set(int index, E e) {
947 rangeCheck(index);
948 checkForComodification();
949 E oldValue = ArrayList.this.elementData(offset + index);
950 ArrayList.this.elementData[offset + index] = e;
951 return oldValue;
952 }
953
954 public E get(int index) {
955 rangeCheck(index);
956 checkForComodification();
957 return ArrayList.this.elementData(offset + index);
958 }
959
960 public int size() {
961 checkForComodification();
962 return this.size;
963 }
964
965 public void add(int index, E e) {
966 rangeCheckForAdd(index);
967 checkForComodification();
968 parent.add(parentOffset + index, e);
969 this.modCount = parent.modCount;
970 this.size++;
971 }
972
973 public E remove(int index) {
974 rangeCheck(index);
975 checkForComodification();
976 E result = parent.remove(parentOffset + index);
977 this.modCount = parent.modCount;
978 this.size--;
979 return result;
980 }
981
982 protected void removeRange(int fromIndex, int toIndex) {
983 checkForComodification();
984 parent.removeRange(parentOffset + fromIndex,
985 parentOffset + toIndex);
986 this.modCount = parent.modCount;
987 this.size -= toIndex - fromIndex;
988 }
989
990 public boolean addAll(Collection<? extends E> c) {
991 return addAll(this.size, c);
992 }
993
994 public boolean addAll(int index, Collection<? extends E> c) {
995 rangeCheckForAdd(index);
996 int cSize = c.size();
997 if (cSize==0)
998 return false;
999
1000 checkForComodification();
1001 parent.addAll(parentOffset + index, c);
1002 this.modCount = parent.modCount;
1003 this.size += cSize;
1004 return true;
1005 }
1006
1007 public Iterator<E> iterator() {
1008 return listIterator();
1009 }
1010
1011 public ListIterator<E> listIterator(final int index) {
1012 checkForComodification();
1013 rangeCheckForAdd(index);
1014 final int offset = this.offset;
1015
1016 return new ListIterator<E>() {
1017 int cursor = index;
1018 int lastRet = -1;
1019 int expectedModCount = ArrayList.this.modCount;
1020
1021 public boolean hasNext() {
1022 return cursor != SubList.this.size;
1023 }
1024
1025 @SuppressWarnings("unchecked")
1026 public E next() {
1027 checkForComodification();
1028 int i = cursor;
1029 if (i >= SubList.this.size)
1030 throw new NoSuchElementException();
1031 Object[] elementData = ArrayList.this.elementData;
1032 if (offset + i >= elementData.length)
1033 throw new ConcurrentModificationException();
1034 cursor = i + 1;
1035 return (E) elementData[offset + (lastRet = i)];
1036 }
1037
1038 public boolean hasPrevious() {
1039 return cursor != 0;
1040 }
1041
1042 @SuppressWarnings("unchecked")
1043 public E previous() {
1044 checkForComodification();
1045 int i = cursor - 1;
1046 if (i < 0)
1047 throw new NoSuchElementException();
1048 Object[] elementData = ArrayList.this.elementData;
1049 if (offset + i >= elementData.length)
1050 throw new ConcurrentModificationException();
1051 cursor = i;
1052 return (E) elementData[offset + (lastRet = i)];
1053 }
1054
1055 public int nextIndex() {
1056 return cursor;
1057 }
1058
1059 public int previousIndex() {
1060 return cursor - 1;
1061 }
1062
1063 public void remove() {
1064 if (lastRet < 0)
1065 throw new IllegalStateException();
1066 checkForComodification();
1067
1068 try {
1069 SubList.this.remove(lastRet);
1070 cursor = lastRet;
1071 lastRet = -1;
1072 expectedModCount = ArrayList.this.modCount;
1073 } catch (IndexOutOfBoundsException ex) {
1074 throw new ConcurrentModificationException();
1075 }
1076 }
1077
1078 public void set(E e) {
1079 if (lastRet < 0)
1080 throw new IllegalStateException();
1081 checkForComodification();
1082
1083 try {
1084 ArrayList.this.set(offset + lastRet, e);
1085 } catch (IndexOutOfBoundsException ex) {
1086 throw new ConcurrentModificationException();
1087 }
1088 }
1089
1090 public void add(E e) {
1091 checkForComodification();
1092
1093 try {
1094 int i = cursor;
1095 SubList.this.add(i, e);
1096 cursor = i + 1;
1097 lastRet = -1;
1098 expectedModCount = ArrayList.this.modCount;
1099 } catch (IndexOutOfBoundsException ex) {
1100 throw new ConcurrentModificationException();
1101 }
1102 }
1103
1104 final void checkForComodification() {
1105 if (expectedModCount != ArrayList.this.modCount)
1106 throw new ConcurrentModificationException();
1107 }
1108 };
1109 }
1110
1111 public List<E> subList(int fromIndex, int toIndex) {
1112 subListRangeCheck(fromIndex, toIndex, size);
1113 return new SubList(this, offset, fromIndex, toIndex);
1114 }
1115
1116 private void rangeCheck(int index) {
1117 if (index < 0 || index >= this.size)
1118 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
1119 }
1120
1121 private void rangeCheckForAdd(int index) {
1122 if (index < 0 || index > this.size)
1123 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
1124 }
1125
1126 private String outOfBoundsMsg(int index) {
1127 return "Index: "+index+", Size: "+this.size;
1128 }
1129
1130 private void checkForComodification() {
1131 if (ArrayList.this.modCount != this.modCount)
1132 throw new ConcurrentModificationException();
1133 }
1134 }
1135
1136 @Override
1137 public void forEach(Block<? super E> block) {
1138 Objects.requireNonNull(block);
1139 final int expectedModCount = modCount;
1140 final E[] elementData = (E[]) this.elementData;
1141 final int size = this.size;
1142 for (int i=0; modCount == expectedModCount && i < size; i++) {
1143 block.accept(elementData[i]);
1144 }
1145 if (modCount != expectedModCount) {
1146 throw new ConcurrentModificationException();
1147 }
1148 }
1149
1150 @Override
1151 public boolean removeAll(Predicate<? super E> filter) {
1152 Objects.requireNonNull(filter);
1153 // figure out which elements are to be removed
1154 // any exception thrown from the filter predicate at this stage
1155 // will leave the collection unmodified
1156 int removeCount = 0;
1157 final BitSet removeSet = new BitSet(size);
1158 final int expectedModCount = modCount;
1159 final int size = this.size;
1160 for (int i=0; modCount == expectedModCount && i < size; i++) {
1161 @SuppressWarnings("unchecked")
1162 final E element = (E) elementData[i];
1163 if (filter.test(element)) {
1164 removeSet.set(i);
1165 removeCount++;
1166 }
1167 }
1168
1169 if (modCount != expectedModCount) {
1170 throw new ConcurrentModificationException();
1171 }
1172
1173 // shift surviving elements left over the spaces left by removed elements
1174 final boolean anyToRemove = removeCount > 0;
1175 if (anyToRemove) {
1176 final int newSize = size - removeCount;
1177 for (int i=0, j=0; modCount == expectedModCount &&
1178 (i < size) && (j < newSize); i++, j++) {
1179 i = removeSet.nextClearBit(i);
1180 elementData[j] = elementData[i];
1181 }
1182 for (int k=newSize; modCount == expectedModCount && k < size; k++) {
1183 elementData[k] = null; // Let gc do its work
1184 }
1185 this.size = newSize;
1186 if (modCount != expectedModCount) {
1187 throw new ConcurrentModificationException();
1188 }
1189 modCount++;
1190 }
1191
1192 return anyToRemove;
1193 }
1194
1195 @Override
1196 @SuppressWarnings("unchecked")
1197 public void replaceAll(UnaryOperator<E> operator) {
1198 Objects.requireNonNull(operator);
1199 final int expectedModCount = modCount;
1200 final int size = this.size;
1201 for (int i=0; modCount == expectedModCount && i < size; i++) {
1202 elementData[i] = operator.operate((E) elementData[i]);
1203 }
1204 if (modCount != expectedModCount) {
1205 throw new ConcurrentModificationException();
1206 }
1207 modCount++;
1208 }
1209
1210 @Override
1211 @SuppressWarnings("unchecked")
1212 public void sort(Comparator<? super E> c) {
1213 Objects.requireNonNull(c);
1214 final int expectedModCount = modCount;
1215 Arrays.sort((E[]) elementData, 0, size, c);
1216 if (modCount != expectedModCount) {
1217 throw new ConcurrentModificationException();
1218 }
1219 modCount++;
1220 }
1221 }