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 /**
29 * Resizable-array implementation of the <tt>List</tt> interface. Implements
30 * all optional list operations, and permits all elements, including
31 * <tt>null</tt>. In addition to implementing the <tt>List</tt> interface,
32 * this class provides methods to manipulate the size of the array that is
33 * used internally to store the list. (This class is roughly equivalent to
34 * <tt>Vector</tt>, except that it is unsynchronized.)
35 *
36 * <p>The <tt>size</tt>, <tt>isEmpty</tt>, <tt>get</tt>, <tt>set</tt>,
37 * <tt>iterator</tt>, and <tt>listIterator</tt> operations run in constant
38 * time. The <tt>add</tt> operation runs in <i>amortized constant time</i>,
39 * that is, adding n elements requires O(n) time. All of the other operations
40 * run in linear time (roughly speaking). The constant factor is low compared
41 * to that for the <tt>LinkedList</tt> implementation.
42 *
43 * <p>Each <tt>ArrayList</tt> instance has a <i>capacity</i>. The capacity is
44 * the size of the array used to store the elements in the list. It is always
45 * at least as large as the list size. As elements are added to an ArrayList,
46 * its capacity grows automatically. The details of the growth policy are not
47 * specified beyond the fact that adding an element has constant amortized
48 * time cost.
49 *
50 * <p>An application can increase the capacity of an <tt>ArrayList</tt> instance
51 * before adding a large number of elements using the <tt>ensureCapacity</tt>
52 * operation. This may reduce the amount of incremental reallocation.
53 *
54 * <p><strong>Note that this implementation is not synchronized.</strong>
55 * If multiple threads access an <tt>ArrayList</tt> instance concurrently,
56 * and at least one of the threads modifies the list structurally, it
57 * <i>must</i> be synchronized externally. (A structural modification is
58 * any operation that adds or deletes one or more elements, or explicitly
59 * resizes the backing array; merely setting the value of an element is not
60 * a structural modification.) This is typically accomplished by
61 * synchronizing on some object that naturally encapsulates the list.
62 *
63 * If no such object exists, the list should be "wrapped" using the
64 * {@link Collections#synchronizedList Collections.synchronizedList}
65 * method. This is best done at creation time, to prevent accidental
66 * unsynchronized access to the list:<pre>
67 * List list = Collections.synchronizedList(new ArrayList(...));</pre>
68 *
69 * <p><a name="fail-fast"/>
70 * The iterators returned by this class's {@link #iterator() iterator} and
71 * {@link #listIterator(int) listIterator} methods are <em>fail-fast</em>:
72 * if the list is structurally modified at any time after the iterator is
73 * created, in any way except through the iterator's own
74 * {@link ListIterator#remove() remove} or
75 * {@link ListIterator#add(Object) add} methods, the iterator will throw a
76 * {@link ConcurrentModificationException}. Thus, in the face of
77 * concurrent modification, the iterator fails quickly and cleanly, rather
78 * than risking arbitrary, non-deterministic behavior at an undetermined
79 * time in the future.
80 *
81 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
82 * as it is, generally speaking, impossible to make any hard guarantees in the
83 * presence of unsynchronized concurrent modification. Fail-fast iterators
84 * throw {@code ConcurrentModificationException} on a best-effort basis.
85 * Therefore, it would be wrong to write a program that depended on this
86 * exception for its correctness: <i>the fail-fast behavior of iterators
87 * should be used only to detect bugs.</i>
88 *
89 * <p>This class is a member of the
90 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
91 * Java Collections Framework</a>.
92 *
93 * @author Josh Bloch
94 * @author Neal Gafter
95 * @see Collection
96 * @see List
97 * @see LinkedList
98 * @see Vector
99 * @since 1.2
100 */
101
102 public class ArrayList<E> extends AbstractList<E>
103 implements List<E>, RandomAccess, Cloneable, java.io.Serializable
104 {
105 private static final long serialVersionUID = 8683452581122892189L;
106
107 /**
108 * The array buffer into which the elements of the ArrayList are stored.
109 * The capacity of the ArrayList is the length of this array buffer.
110 */
111 private transient Object[] elementData;
112
113 /**
114 * The size of the ArrayList (the number of elements it contains).
115 *
116 * @serial
117 */
118 private int size;
119
120 /**
121 * Constructs an empty list with the specified initial capacity.
122 *
123 * @param initialCapacity the initial capacity of the list
124 * @throws IllegalArgumentException if the specified initial capacity
125 * is negative
126 */
127 public ArrayList(int initialCapacity) {
128 super();
129 if (initialCapacity < 0)
130 throw new IllegalArgumentException("Illegal Capacity: "+
131 initialCapacity);
132 this.elementData = new Object[initialCapacity];
133 }
134
135 /**
136 * Constructs an empty list with an initial capacity of ten.
137 */
138 public ArrayList() {
139 this(10);
140 }
141
142 /**
143 * Constructs a list containing the elements of the specified
144 * collection, in the order they are returned by the collection's
145 * iterator.
146 *
147 * @param c the collection whose elements are to be placed into this list
148 * @throws NullPointerException if the specified collection is null
149 */
150 public ArrayList(Collection<? extends E> c) {
151 elementData = c.toArray();
152 size = elementData.length;
153 // c.toArray might (incorrectly) not return Object[] (see 6260652)
154 if (elementData.getClass() != Object[].class)
155 elementData = Arrays.copyOf(elementData, size, Object[].class);
156 }
157
158 /**
159 * Trims the capacity of this <tt>ArrayList</tt> instance to be the
160 * list's current size. An application can use this operation to minimize
161 * the storage of an <tt>ArrayList</tt> instance.
162 */
163 public void trimToSize() {
164 modCount++;
165 int oldCapacity = elementData.length;
166 if (size < oldCapacity) {
167 elementData = Arrays.copyOf(elementData, size);
168 }
169 }
170
171 /**
172 * Increases the capacity of this <tt>ArrayList</tt> instance, if
173 * necessary, to ensure that it can hold at least the number of elements
174 * specified by the minimum capacity argument.
175 *
176 * @param minCapacity the desired minimum capacity
177 */
178 public void ensureCapacity(int minCapacity) {
179 if (minCapacity > 0)
180 ensureCapacityInternal(minCapacity);
181 }
182
183 private void ensureCapacityInternal(int minCapacity) {
184 modCount++;
185 // overflow-conscious code
186 if (minCapacity - elementData.length > 0)
187 grow(minCapacity);
188 }
189
190 /**
191 * The maximum size of array to allocate.
192 * Some VMs reserve some header words in an array.
193 * Attempts to allocate larger arrays may result in
194 * OutOfMemoryError: Requested array size exceeds VM limit
195 */
196 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
197
198 /**
199 * Increases the capacity to ensure that it can hold at least the
200 * number of elements specified by the minimum capacity argument.
201 *
202 * @param minCapacity the desired minimum capacity
203 */
204 private void grow(int minCapacity) {
205 // overflow-conscious code
206 int oldCapacity = elementData.length;
207 int newCapacity = oldCapacity + (oldCapacity >> 1);
208 if (newCapacity - minCapacity < 0)
209 newCapacity = minCapacity;
210 if (newCapacity - MAX_ARRAY_SIZE > 0)
211 newCapacity = hugeCapacity(minCapacity);
212 // minCapacity is usually close to size, so this is a win:
213 elementData = Arrays.copyOf(elementData, newCapacity);
214 }
215
216 private static int hugeCapacity(int minCapacity) {
217 if (minCapacity < 0) // overflow
218 throw new OutOfMemoryError();
219 return (minCapacity > MAX_ARRAY_SIZE) ?
220 Integer.MAX_VALUE :
221 MAX_ARRAY_SIZE;
222 }
223
224 /**
225 * Returns the number of elements in this list.
226 *
227 * @return the number of elements in this list
228 */
229 public int size() {
230 return size;
231 }
232
233 /**
234 * Returns <tt>true</tt> if this list contains no elements.
235 *
236 * @return <tt>true</tt> if this list contains no elements
237 */
238 public boolean isEmpty() {
239 return size == 0;
240 }
241
242 /**
243 * Returns <tt>true</tt> if this list contains the specified element.
244 * More formally, returns <tt>true</tt> if and only if this list contains
245 * at least one element <tt>e</tt> such that
246 * <tt>(o==null ? e==null : o.equals(e))</tt>.
247 *
248 * @param o element whose presence in this list is to be tested
249 * @return <tt>true</tt> if this list contains the specified element
250 */
251 public boolean contains(Object o) {
252 return indexOf(o) >= 0;
253 }
254
255 /**
256 * Returns the index of the first occurrence of the specified element
257 * in this list, or -1 if this list does not contain the element.
258 * More formally, returns the lowest index <tt>i</tt> such that
259 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
260 * or -1 if there is no such index.
261 */
262 public int indexOf(Object o) {
263 if (o == null) {
264 for (int i = 0; i < size; i++)
265 if (elementData[i]==null)
266 return i;
267 } else {
268 for (int i = 0; i < size; i++)
269 if (o.equals(elementData[i]))
270 return i;
271 }
272 return -1;
273 }
274
275 /**
276 * Returns the index of the last occurrence of the specified element
277 * in this list, or -1 if this list does not contain the element.
278 * More formally, returns the highest index <tt>i</tt> such that
279 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
280 * or -1 if there is no such index.
281 */
282 public int lastIndexOf(Object o) {
283 if (o == null) {
284 for (int i = size-1; i >= 0; i--)
285 if (elementData[i]==null)
286 return i;
287 } else {
288 for (int i = size-1; i >= 0; i--)
289 if (o.equals(elementData[i]))
290 return i;
291 }
292 return -1;
293 }
294
295 /**
296 * Returns a shallow copy of this <tt>ArrayList</tt> instance. (The
297 * elements themselves are not copied.)
298 *
299 * @return a clone of this <tt>ArrayList</tt> instance
300 */
301 public Object clone() {
302 try {
303 ArrayList<?> v = (ArrayList<?>) super.clone();
304 v.elementData = Arrays.copyOf(elementData, size);
305 v.modCount = 0;
306 return v;
307 } catch (CloneNotSupportedException e) {
308 // this shouldn't happen, since we are Cloneable
309 throw new InternalError(e);
310 }
311 }
312
313 /**
314 * Returns an array containing all of the elements in this list
315 * in proper sequence (from first to last element).
316 *
317 * <p>The returned array will be "safe" in that no references to it are
318 * maintained by this list. (In other words, this method must allocate
319 * a new array). The caller is thus free to modify the returned array.
320 *
321 * <p>This method acts as bridge between array-based and collection-based
322 * APIs.
323 *
324 * @return an array containing all of the elements in this list in
325 * proper sequence
326 */
327 public Object[] toArray() {
328 return Arrays.copyOf(elementData, size);
329 }
330
331 /**
332 * Returns an array containing all of the elements in this list in proper
333 * sequence (from first to last element); the runtime type of the returned
334 * array is that of the specified array. If the list fits in the
335 * specified array, it is returned therein. Otherwise, a new array is
336 * allocated with the runtime type of the specified array and the size of
337 * this list.
338 *
339 * <p>If the list fits in the specified array with room to spare
340 * (i.e., the array has more elements than the list), the element in
341 * the array immediately following the end of the collection is set to
342 * <tt>null</tt>. (This is useful in determining the length of the
343 * list <i>only</i> if the caller knows that the list does not contain
344 * any null elements.)
345 *
346 * @param a the array into which the elements of the list are to
347 * be stored, if it is big enough; otherwise, a new array of the
348 * same runtime type is allocated for this purpose.
349 * @return an array containing the elements of the list
350 * @throws ArrayStoreException if the runtime type of the specified array
351 * is not a supertype of the runtime type of every element in
352 * this list
353 * @throws NullPointerException if the specified array is null
354 */
355 @SuppressWarnings("unchecked")
356 public <T> T[] toArray(T[] a) {
357 if (a.length < size)
358 // Make a new array of a's runtime type, but my contents:
359 return (T[]) Arrays.copyOf(elementData, size, a.getClass());
360 System.arraycopy(elementData, 0, a, 0, size);
361 if (a.length > size)
362 a[size] = null;
363 return a;
364 }
365
366 // Positional Access Operations
367
368 @SuppressWarnings("unchecked")
369 E elementData(int index) {
370 return (E) elementData[index];
371 }
372
373 /**
374 * Returns the element at the specified position in this list.
375 *
376 * @param index index of the element to return
377 * @return the element at the specified position in this list
378 * @throws IndexOutOfBoundsException {@inheritDoc}
379 */
380 public E get(int index) {
381 rangeCheck(index);
382
383 return elementData(index);
384 }
385
386 /**
387 * Replaces the element at the specified position in this list with
388 * the specified element.
389 *
390 * @param index index of the element to replace
391 * @param element element to be stored at the specified position
392 * @return the element previously at the specified position
393 * @throws IndexOutOfBoundsException {@inheritDoc}
394 */
395 public E set(int index, E element) {
396 rangeCheck(index);
397
398 E oldValue = elementData(index);
399 elementData[index] = element;
400 return oldValue;
401 }
402
403 /**
404 * Appends the specified element to the end of this list.
405 *
406 * @param e element to be appended to this list
407 * @return <tt>true</tt> (as specified by {@link Collection#add})
408 */
409 public boolean add(E e) {
410 ensureCapacityInternal(size + 1); // Increments modCount!!
411 elementData[size++] = e;
412 return true;
413 }
414
415 /**
416 * Inserts the specified element at the specified position in this
417 * list. Shifts the element currently at that position (if any) and
418 * any subsequent elements to the right (adds one to their indices).
419 *
420 * @param index index at which the specified element is to be inserted
421 * @param element element to be inserted
422 * @throws IndexOutOfBoundsException {@inheritDoc}
423 */
424 public void add(int index, E element) {
425 rangeCheckForAdd(index);
426
427 ensureCapacityInternal(size + 1); // Increments modCount!!
428 System.arraycopy(elementData, index, elementData, index + 1,
429 size - index);
430 elementData[index] = element;
431 size++;
432 }
433
434 /**
435 * Removes the element at the specified position in this list.
436 * Shifts any subsequent elements to the left (subtracts one from their
437 * indices).
438 *
439 * @param index the index of the element to be removed
440 * @return the element that was removed from the list
441 * @throws IndexOutOfBoundsException {@inheritDoc}
442 */
443 public E remove(int index) {
444 rangeCheck(index);
445
446 modCount++;
447 E oldValue = elementData(index);
448
449 int numMoved = size - index - 1;
450 if (numMoved > 0)
451 System.arraycopy(elementData, index+1, elementData, index,
452 numMoved);
453 elementData[--size] = null; // Let gc do its work
454
455 return oldValue;
456 }
457
458 /**
459 * Removes the first occurrence of the specified element from this list,
460 * if it is present. If the list does not contain the element, it is
461 * unchanged. More formally, removes the element with the lowest index
462 * <tt>i</tt> such that
463 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>
464 * (if such an element exists). Returns <tt>true</tt> if this list
465 * contained the specified element (or equivalently, if this list
466 * changed as a result of the call).
467 *
468 * @param o element to be removed from this list, if present
469 * @return <tt>true</tt> if this list contained the specified element
470 */
471 public boolean remove(Object o) {
472 if (o == null) {
473 for (int index = 0; index < size; index++)
474 if (elementData[index] == null) {
475 fastRemove(index);
476 return true;
477 }
478 } else {
479 for (int index = 0; index < size; index++)
480 if (o.equals(elementData[index])) {
481 fastRemove(index);
482 return true;
483 }
484 }
485 return false;
486 }
487
488 /*
489 * Private remove method that skips bounds checking and does not
490 * return the value removed.
491 */
492 private void fastRemove(int index) {
493 modCount++;
494 int numMoved = size - index - 1;
495 if (numMoved > 0)
496 System.arraycopy(elementData, index+1, elementData, index,
497 numMoved);
498 elementData[--size] = null; // Let gc do its work
499 }
500
501 /**
502 * Removes all of the elements from this list. The list will
503 * be empty after this call returns.
504 */
505 public void clear() {
506 modCount++;
507
508 // Let gc do its work
509 for (int i = 0; i < size; i++)
510 elementData[i] = null;
511
512 size = 0;
513 }
514
515 /**
516 * Appends all of the elements in the specified collection to the end of
517 * this list, in the order that they are returned by the
518 * specified collection's Iterator. The behavior of this operation is
519 * undefined if the specified collection is modified while the operation
520 * is in progress. (This implies that the behavior of this call is
521 * undefined if the specified collection is this list, and this
522 * list is nonempty.)
523 *
524 * @param c collection containing elements to be added to this list
525 * @return <tt>true</tt> if this list changed as a result of the call
526 * @throws NullPointerException if the specified collection is null
527 */
528 public boolean addAll(Collection<? extends E> c) {
529 Object[] a = c.toArray();
530 int numNew = a.length;
531 ensureCapacityInternal(size + numNew); // Increments modCount
532 System.arraycopy(a, 0, elementData, size, numNew);
533 size += numNew;
534 return numNew != 0;
535 }
536
537 /**
538 * Inserts all of the elements in the specified collection into this
539 * list, starting at the specified position. Shifts the element
540 * currently at that position (if any) and any subsequent elements to
541 * the right (increases their indices). The new elements will appear
542 * in the list in the order that they are returned by the
543 * specified collection's iterator.
544 *
545 * @param index index at which to insert the first element from the
546 * specified collection
547 * @param c collection containing elements to be added to this list
548 * @return <tt>true</tt> if this list changed as a result of the call
549 * @throws IndexOutOfBoundsException {@inheritDoc}
550 * @throws NullPointerException if the specified collection is null
551 */
552 public boolean addAll(int index, Collection<? extends E> c) {
553 rangeCheckForAdd(index);
554
555 Object[] a = c.toArray();
556 int numNew = a.length;
557 ensureCapacityInternal(size + numNew); // Increments modCount
558
559 int numMoved = size - index;
560 if (numMoved > 0)
561 System.arraycopy(elementData, index, elementData, index + numNew,
562 numMoved);
563
564 System.arraycopy(a, 0, elementData, index, numNew);
565 size += numNew;
566 return numNew != 0;
567 }
568
569 /**
570 * Removes from this list all of the elements whose index is between
571 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
572 * Shifts any succeeding elements to the left (reduces their index).
573 * This call shortens the list by {@code (toIndex - fromIndex)} elements.
574 * (If {@code toIndex==fromIndex}, this operation has no effect.)
575 *
576 * @throws IndexOutOfBoundsException if {@code fromIndex} or
577 * {@code toIndex} is out of range
578 * ({@code fromIndex < 0 ||
579 * fromIndex >= size() ||
580 * toIndex > size() ||
581 * toIndex < fromIndex})
582 */
583 protected void removeRange(int fromIndex, int toIndex) {
584 modCount++;
585 int numMoved = size - toIndex;
586 System.arraycopy(elementData, toIndex, elementData, fromIndex,
587 numMoved);
588
589 // Let gc do its work
590 int newSize = size - (toIndex-fromIndex);
591 while (size != newSize)
592 elementData[--size] = null;
593 }
594
595 /**
596 * Checks if the given index is in range. If not, throws an appropriate
597 * runtime exception. This method does *not* check if the index is
598 * negative: It is always used immediately prior to an array access,
599 * which throws an ArrayIndexOutOfBoundsException if index is negative.
600 */
601 private void rangeCheck(int index) {
602 if (index >= size)
603 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
604 }
605
606 /**
607 * A version of rangeCheck used by add and addAll.
608 */
609 private void rangeCheckForAdd(int index) {
610 if (index > size || index < 0)
611 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
612 }
613
614 /**
615 * Constructs an IndexOutOfBoundsException detail message.
616 * Of the many possible refactorings of the error handling code,
617 * this "outlining" performs best with both server and client VMs.
618 */
619 private String outOfBoundsMsg(int index) {
620 return "Index: "+index+", Size: "+size;
621 }
622
623 /**
624 * Removes from this list all of its elements that are contained in the
625 * specified collection.
626 *
627 * @param c collection containing elements to be removed from this list
628 * @return {@code true} if this list changed as a result of the call
629 * @throws ClassCastException if the class of an element of this list
630 * is incompatible with the specified collection
631 * (<a href="Collection.html#optional-restrictions">optional</a>)
632 * @throws NullPointerException if this list contains a null element and the
633 * specified collection does not permit null elements
634 * (<a href="Collection.html#optional-restrictions">optional</a>),
635 * or if the specified collection is null
636 * @see Collection#contains(Object)
637 */
638 public boolean removeAll(Collection<?> c) {
639 return batchRemove(c, false);
640 }
641
642 /**
643 * Retains only the elements in this list that are contained in the
644 * specified collection. In other words, removes from this list all
645 * of its elements that are not contained in the specified collection.
646 *
647 * @param c collection containing elements to be retained in this list
648 * @return {@code true} if this list changed as a result of the call
649 * @throws ClassCastException if the class of an element of this list
650 * is incompatible with the specified collection
651 * (<a href="Collection.html#optional-restrictions">optional</a>)
652 * @throws NullPointerException if this list contains a null element and the
653 * specified collection does not permit null elements
654 * (<a href="Collection.html#optional-restrictions">optional</a>),
655 * or if the specified collection is null
656 * @see Collection#contains(Object)
657 */
658 public boolean retainAll(Collection<?> c) {
659 return batchRemove(c, true);
660 }
661
662 private boolean batchRemove(Collection<?> c, boolean complement) {
663 final Object[] elementData = this.elementData;
664 int r = 0, w = 0;
665 boolean modified = false;
666 try {
667 for (; r < size; r++)
668 if (c.contains(elementData[r]) == complement)
669 elementData[w++] = elementData[r];
670 } finally {
671 // Preserve behavioral compatibility with AbstractCollection,
672 // even if c.contains() throws.
673 if (r != size) {
674 System.arraycopy(elementData, r,
675 elementData, w,
676 size - r);
677 w += size - r;
678 }
679 if (w != size) {
680 for (int i = w; i < size; i++)
681 elementData[i] = null;
682 modCount += size - w;
683 size = w;
684 modified = true;
685 }
686 }
687 return modified;
688 }
689
690 /**
691 * Save the state of the <tt>ArrayList</tt> instance to a stream (that
692 * is, serialize it).
693 *
694 * @serialData The length of the array backing the <tt>ArrayList</tt>
695 * instance is emitted (int), followed by all of its elements
696 * (each an <tt>Object</tt>) in the proper order.
697 */
698 private void writeObject(java.io.ObjectOutputStream s)
699 throws java.io.IOException{
700 // Write out element count, and any hidden stuff
701 int expectedModCount = modCount;
702 s.defaultWriteObject();
703
704 // Write out array length
705 s.writeInt(elementData.length);
706
707 // Write out all elements in the proper order.
708 for (int i=0; i<size; i++)
709 s.writeObject(elementData[i]);
710
711 if (modCount != expectedModCount) {
712 throw new ConcurrentModificationException();
713 }
714
715 }
716
717 /**
718 * Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
719 * deserialize it).
720 */
721 private void readObject(java.io.ObjectInputStream s)
722 throws java.io.IOException, ClassNotFoundException {
723 // Read in size, and any hidden stuff
724 s.defaultReadObject();
725
726 // Read in array length and allocate array
727 int arrayLength = s.readInt();
728 Object[] a = elementData = new Object[arrayLength];
729
730 // Read in all elements in the proper order.
731 for (int i=0; i<size; i++)
732 a[i] = s.readObject();
733 }
734
735 /**
736 * Returns a list iterator over the elements in this list (in proper
737 * sequence), starting at the specified position in the list.
738 * The specified index indicates the first element that would be
739 * returned by an initial call to {@link ListIterator#next next}.
740 * An initial call to {@link ListIterator#previous previous} would
741 * return the element with the specified index minus one.
742 *
743 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
744 *
745 * @throws IndexOutOfBoundsException {@inheritDoc}
746 */
747 public ListIterator<E> listIterator(int index) {
748 if (index < 0 || index > size)
749 throw new IndexOutOfBoundsException("Index: "+index);
750 return new ListItr(index);
751 }
752
753 /**
754 * Returns a list iterator over the elements in this list (in proper
755 * sequence).
756 *
757 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
758 *
759 * @see #listIterator(int)
760 */
761 public ListIterator<E> listIterator() {
762 return new ListItr(0);
763 }
764
765 /**
766 * Returns an iterator over the elements in this list in proper sequence.
767 *
768 * <p>The returned iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
769 *
770 * @return an iterator over the elements in this list in proper sequence
771 */
772 public Iterator<E> iterator() {
773 return new Itr();
774 }
775
776 /**
777 * An optimized version of AbstractList.Itr
778 */
779 private class Itr implements Iterator<E> {
780 int cursor; // index of next element to return
781 int lastRet = -1; // index of last element returned; -1 if no such
782 int expectedModCount = modCount;
783
784 public boolean hasNext() {
785 return cursor != size;
786 }
787
788 @SuppressWarnings("unchecked")
789 public E next() {
790 checkForComodification();
791 int i = cursor;
792 if (i >= size)
793 throw new NoSuchElementException();
794 Object[] elementData = ArrayList.this.elementData;
795 if (i >= elementData.length)
796 throw new ConcurrentModificationException();
797 cursor = i + 1;
798 return (E) elementData[lastRet = i];
799 }
800
801 public void remove() {
802 if (lastRet < 0)
803 throw new IllegalStateException();
804 checkForComodification();
805
806 try {
807 ArrayList.this.remove(lastRet);
808 cursor = lastRet;
809 lastRet = -1;
810 expectedModCount = modCount;
811 } catch (IndexOutOfBoundsException ex) {
812 throw new ConcurrentModificationException();
813 }
814 }
815
816 final void checkForComodification() {
817 if (modCount != expectedModCount)
818 throw new ConcurrentModificationException();
819 }
820 }
821
822 /**
823 * An optimized version of AbstractList.ListItr
824 */
825 private class ListItr extends Itr implements ListIterator<E> {
826 ListItr(int index) {
827 super();
828 cursor = index;
829 }
830
831 public boolean hasPrevious() {
832 return cursor != 0;
833 }
834
835 public int nextIndex() {
836 return cursor;
837 }
838
839 public int previousIndex() {
840 return cursor - 1;
841 }
842
843 @SuppressWarnings("unchecked")
844 public E previous() {
845 checkForComodification();
846 int i = cursor - 1;
847 if (i < 0)
848 throw new NoSuchElementException();
849 Object[] elementData = ArrayList.this.elementData;
850 if (i >= elementData.length)
851 throw new ConcurrentModificationException();
852 cursor = i;
853 return (E) elementData[lastRet = i];
854 }
855
856 public void set(E e) {
857 if (lastRet < 0)
858 throw new IllegalStateException();
859 checkForComodification();
860
861 try {
862 ArrayList.this.set(lastRet, e);
863 } catch (IndexOutOfBoundsException ex) {
864 throw new ConcurrentModificationException();
865 }
866 }
867
868 public void add(E e) {
869 checkForComodification();
870
871 try {
872 int i = cursor;
873 ArrayList.this.add(i, e);
874 cursor = i + 1;
875 lastRet = -1;
876 expectedModCount = modCount;
877 } catch (IndexOutOfBoundsException ex) {
878 throw new ConcurrentModificationException();
879 }
880 }
881 }
882
883 /**
884 * Returns a view of the portion of this list between the specified
885 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. (If
886 * {@code fromIndex} and {@code toIndex} are equal, the returned list is
887 * empty.) The returned list is backed by this list, so non-structural
888 * changes in the returned list are reflected in this list, and vice-versa.
889 * The returned list supports all of the optional list operations.
890 *
891 * <p>This method eliminates the need for explicit range operations (of
892 * the sort that commonly exist for arrays). Any operation that expects
893 * a list can be used as a range operation by passing a subList view
894 * instead of a whole list. For example, the following idiom
895 * removes a range of elements from a list:
896 * <pre>
897 * list.subList(from, to).clear();
898 * </pre>
899 * Similar idioms may be constructed for {@link #indexOf(Object)} and
900 * {@link #lastIndexOf(Object)}, and all of the algorithms in the
901 * {@link Collections} class can be applied to a subList.
902 *
903 * <p>The semantics of the list returned by this method become undefined if
904 * the backing list (i.e., this list) is <i>structurally modified</i> in
905 * any way other than via the returned list. (Structural modifications are
906 * those that change the size of this list, or otherwise perturb it in such
907 * a fashion that iterations in progress may yield incorrect results.)
908 *
909 * @throws IndexOutOfBoundsException {@inheritDoc}
910 * @throws IllegalArgumentException {@inheritDoc}
911 */
912 public List<E> subList(int fromIndex, int toIndex) {
913 subListRangeCheck(fromIndex, toIndex, size);
914 return new SubList(this, 0, fromIndex, toIndex);
915 }
916
917 static void subListRangeCheck(int fromIndex, int toIndex, int size) {
918 if (fromIndex < 0)
919 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
920 if (toIndex > size)
921 throw new IndexOutOfBoundsException("toIndex = " + toIndex);
922 if (fromIndex > toIndex)
923 throw new IllegalArgumentException("fromIndex(" + fromIndex +
924 ") > toIndex(" + toIndex + ")");
925 }
926
927 private class SubList extends AbstractList<E> implements RandomAccess {
928 private final AbstractList<E> parent;
929 private final int parentOffset;
930 private final int offset;
931 int size;
932
933 SubList(AbstractList<E> parent,
934 int offset, int fromIndex, int toIndex) {
935 this.parent = parent;
936 this.parentOffset = fromIndex;
937 this.offset = offset + fromIndex;
938 this.size = toIndex - fromIndex;
939 this.modCount = ArrayList.this.modCount;
940 }
941
942 public E set(int index, E e) {
943 rangeCheck(index);
944 checkForComodification();
945 E oldValue = ArrayList.this.elementData(offset + index);
946 ArrayList.this.elementData[offset + index] = e;
947 return oldValue;
948 }
949
950 public E get(int index) {
951 rangeCheck(index);
952 checkForComodification();
953 return ArrayList.this.elementData(offset + index);
954 }
955
956 public int size() {
957 checkForComodification();
958 return this.size;
959 }
960
961 public void add(int index, E e) {
962 rangeCheckForAdd(index);
963 checkForComodification();
964 parent.add(parentOffset + index, e);
965 this.modCount = parent.modCount;
966 this.size++;
967 }
968
969 public E remove(int index) {
970 rangeCheck(index);
971 checkForComodification();
972 E result = parent.remove(parentOffset + index);
973 this.modCount = parent.modCount;
974 this.size--;
975 return result;
976 }
977
978 protected void removeRange(int fromIndex, int toIndex) {
979 checkForComodification();
980 parent.removeRange(parentOffset + fromIndex,
981 parentOffset + toIndex);
982 this.modCount = parent.modCount;
983 this.size -= toIndex - fromIndex;
984 }
985
986 public boolean addAll(Collection<? extends E> c) {
987 return addAll(this.size, c);
988 }
989
990 public boolean addAll(int index, Collection<? extends E> c) {
991 rangeCheckForAdd(index);
992 int cSize = c.size();
993 if (cSize==0)
994 return false;
995
996 checkForComodification();
997 parent.addAll(parentOffset + index, c);
998 this.modCount = parent.modCount;
999 this.size += cSize;
1000 return true;
1001 }
1002
1003 public Iterator<E> iterator() {
1004 return listIterator();
1005 }
1006
1007 public ListIterator<E> listIterator(final int index) {
1008 checkForComodification();
1009 rangeCheckForAdd(index);
1010 final int offset = this.offset;
1011
1012 return new ListIterator<E>() {
1013 int cursor = index;
1014 int lastRet = -1;
1015 int expectedModCount = ArrayList.this.modCount;
1016
1017 public boolean hasNext() {
1018 return cursor != SubList.this.size;
1019 }
1020
1021 @SuppressWarnings("unchecked")
1022 public E next() {
1023 checkForComodification();
1024 int i = cursor;
1025 if (i >= SubList.this.size)
1026 throw new NoSuchElementException();
1027 Object[] elementData = ArrayList.this.elementData;
1028 if (offset + i >= elementData.length)
1029 throw new ConcurrentModificationException();
1030 cursor = i + 1;
1031 return (E) elementData[offset + (lastRet = i)];
1032 }
1033
1034 public boolean hasPrevious() {
1035 return cursor != 0;
1036 }
1037
1038 @SuppressWarnings("unchecked")
1039 public E previous() {
1040 checkForComodification();
1041 int i = cursor - 1;
1042 if (i < 0)
1043 throw new NoSuchElementException();
1044 Object[] elementData = ArrayList.this.elementData;
1045 if (offset + i >= elementData.length)
1046 throw new ConcurrentModificationException();
1047 cursor = i;
1048 return (E) elementData[offset + (lastRet = i)];
1049 }
1050
1051 public int nextIndex() {
1052 return cursor;
1053 }
1054
1055 public int previousIndex() {
1056 return cursor - 1;
1057 }
1058
1059 public void remove() {
1060 if (lastRet < 0)
1061 throw new IllegalStateException();
1062 checkForComodification();
1063
1064 try {
1065 SubList.this.remove(lastRet);
1066 cursor = lastRet;
1067 lastRet = -1;
1068 expectedModCount = ArrayList.this.modCount;
1069 } catch (IndexOutOfBoundsException ex) {
1070 throw new ConcurrentModificationException();
1071 }
1072 }
1073
1074 public void set(E e) {
1075 if (lastRet < 0)
1076 throw new IllegalStateException();
1077 checkForComodification();
1078
1079 try {
1080 ArrayList.this.set(offset + lastRet, e);
1081 } catch (IndexOutOfBoundsException ex) {
1082 throw new ConcurrentModificationException();
1083 }
1084 }
1085
1086 public void add(E e) {
1087 checkForComodification();
1088
1089 try {
1090 int i = cursor;
1091 SubList.this.add(i, e);
1092 cursor = i + 1;
1093 lastRet = -1;
1094 expectedModCount = ArrayList.this.modCount;
1095 } catch (IndexOutOfBoundsException ex) {
1096 throw new ConcurrentModificationException();
1097 }
1098 }
1099
1100 final void checkForComodification() {
1101 if (expectedModCount != ArrayList.this.modCount)
1102 throw new ConcurrentModificationException();
1103 }
1104 };
1105 }
1106
1107 public List<E> subList(int fromIndex, int toIndex) {
1108 subListRangeCheck(fromIndex, toIndex, size);
1109 return new SubList(this, offset, fromIndex, toIndex);
1110 }
1111
1112 private void rangeCheck(int index) {
1113 if (index < 0 || index >= this.size)
1114 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
1115 }
1116
1117 private void rangeCheckForAdd(int index) {
1118 if (index < 0 || index > this.size)
1119 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
1120 }
1121
1122 private String outOfBoundsMsg(int index) {
1123 return "Index: "+index+", Size: "+this.size;
1124 }
1125
1126 private void checkForComodification() {
1127 if (ArrayList.this.modCount != this.modCount)
1128 throw new ConcurrentModificationException();
1129 }
1130 }
1131 }