1 /*
2 * Copyright 1997-2007 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.util;
27
28 /**
29 * This class provides a skeletal implementation of the {@link List}
30 * interface to minimize the effort required to implement this interface
31 * backed by a "random access" data store (such as an array). For sequential
32 * access data (such as a linked list), {@link AbstractSequentialList} should
33 * be used in preference to this class.
34 *
35 * <p>To implement an unmodifiable list, the programmer needs only to extend
36 * this class and provide implementations for the {@link #get(int)} and
37 * {@link List#size() size()} methods.
38 *
39 * <p>To implement a modifiable list, the programmer must additionally
40 * override the {@link #set(int, Object) set(int, E)} method (which otherwise
41 * throws an {@code UnsupportedOperationException}). If the list is
42 * variable-size the programmer must additionally override the
43 * {@link #add(int, Object) add(int, E)} and {@link #remove(int)} methods.
44 *
45 * <p>The programmer should generally provide a void (no argument) and collection
46 * constructor, as per the recommendation in the {@link Collection} interface
47 * specification.
48 *
49 * <p>Unlike the other abstract collection implementations, the programmer does
50 * <i>not</i> have to provide an iterator implementation; the iterator and
51 * list iterator are implemented by this class, on top of the "random access"
52 * methods:
53 * {@link #get(int)},
54 * {@link #set(int, Object) set(int, E)},
55 * {@link #add(int, Object) add(int, E)} and
56 * {@link #remove(int)}.
57 *
58 * <p>The documentation for each non-abstract method in this class describes its
59 * implementation in detail. Each of these methods may be overridden if the
60 * collection being implemented admits a more efficient implementation.
61 *
62 * <p>This class is a member of the
63 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
64 * Java Collections Framework</a>.
65 *
66 * @author Josh Bloch
67 * @author Neal Gafter
68 * @since 1.2
69 */
70
71 public abstract class AbstractList<E> extends AbstractCollection<E> implements List<E> {
72 /**
73 * Sole constructor. (For invocation by subclass constructors, typically
74 * implicit.)
75 */
76 protected AbstractList() {
77 }
78
79 /**
80 * Appends the specified element to the end of this list (optional
81 * operation).
82 *
83 * <p>Lists that support this operation may place limitations on what
84 * elements may be added to this list. In particular, some
85 * lists will refuse to add null elements, and others will impose
86 * restrictions on the type of elements that may be added. List
87 * classes should clearly specify in their documentation any restrictions
88 * on what elements may be added.
89 *
90 * <p>This implementation calls {@code add(size(), e)}.
91 *
92 * <p>Note that this implementation throws an
93 * {@code UnsupportedOperationException} unless
94 * {@link #add(int, Object) add(int, E)} is overridden.
95 *
96 * @param e element to be appended to this list
97 * @return {@code true} (as specified by {@link Collection#add})
98 * @throws UnsupportedOperationException if the {@code add} operation
99 * is not supported by this list
100 * @throws ClassCastException if the class of the specified element
101 * prevents it from being added to this list
102 * @throws NullPointerException if the specified element is null and this
103 * list does not permit null elements
104 * @throws IllegalArgumentException if some property of this element
105 * prevents it from being added to this list
106 */
107 public boolean add(E e) {
108 add(size(), e);
109 return true;
110 }
111
112 /**
113 * {@inheritDoc}
114 *
115 * @throws IndexOutOfBoundsException {@inheritDoc}
116 */
117 abstract public E get(int index);
118
119 /**
120 * {@inheritDoc}
121 *
122 * <p>This implementation always throws an
123 * {@code UnsupportedOperationException}.
124 *
125 * @throws UnsupportedOperationException {@inheritDoc}
126 * @throws ClassCastException {@inheritDoc}
127 * @throws NullPointerException {@inheritDoc}
128 * @throws IllegalArgumentException {@inheritDoc}
129 * @throws IndexOutOfBoundsException {@inheritDoc}
130 */
131 public E set(int index, E element) {
132 throw new UnsupportedOperationException();
133 }
134
135 /**
136 * {@inheritDoc}
137 *
138 * <p>This implementation always throws an
139 * {@code UnsupportedOperationException}.
140 *
141 * @throws UnsupportedOperationException {@inheritDoc}
142 * @throws ClassCastException {@inheritDoc}
143 * @throws NullPointerException {@inheritDoc}
144 * @throws IllegalArgumentException {@inheritDoc}
145 * @throws IndexOutOfBoundsException {@inheritDoc}
146 */
147 public void add(int index, E element) {
148 throw new UnsupportedOperationException();
149 }
150
151 /**
152 * {@inheritDoc}
153 *
154 * <p>This implementation always throws an
155 * {@code UnsupportedOperationException}.
156 *
157 * @throws UnsupportedOperationException {@inheritDoc}
158 * @throws IndexOutOfBoundsException {@inheritDoc}
159 */
160 public E remove(int index) {
161 throw new UnsupportedOperationException();
162 }
163
164
165 // Search Operations
166
167 /**
168 * {@inheritDoc}
169 *
170 * <p>This implementation first gets a list iterator (with
171 * {@code listIterator()}). Then, it iterates over the list until the
172 * specified element is found or the end of the list is reached.
173 *
174 * @throws ClassCastException {@inheritDoc}
175 * @throws NullPointerException {@inheritDoc}
176 */
177 public int indexOf(Object o) {
178 ListIterator<E> e = listIterator();
179 if (o==null) {
180 while (e.hasNext())
181 if (e.next()==null)
182 return e.previousIndex();
183 } else {
184 while (e.hasNext())
185 if (o.equals(e.next()))
186 return e.previousIndex();
187 }
188 return -1;
189 }
190
191 /**
192 * {@inheritDoc}
193 *
194 * <p>This implementation first gets a list iterator that points to the end
195 * of the list (with {@code listIterator(size())}). Then, it iterates
196 * backwards over the list until the specified element is found, or the
197 * beginning of the list is reached.
198 *
199 * @throws ClassCastException {@inheritDoc}
200 * @throws NullPointerException {@inheritDoc}
201 */
202 public int lastIndexOf(Object o) {
203 ListIterator<E> e = listIterator(size());
204 if (o==null) {
205 while (e.hasPrevious())
206 if (e.previous()==null)
207 return e.nextIndex();
208 } else {
209 while (e.hasPrevious())
210 if (o.equals(e.previous()))
211 return e.nextIndex();
212 }
213 return -1;
214 }
215
216
217 // Bulk Operations
218
219 /**
220 * Removes all of the elements from this list (optional operation).
221 * The list will be empty after this call returns.
222 *
223 * <p>This implementation calls {@code removeRange(0, size())}.
224 *
225 * <p>Note that this implementation throws an
226 * {@code UnsupportedOperationException} unless {@code remove(int
227 * index)} or {@code removeRange(int fromIndex, int toIndex)} is
228 * overridden.
229 *
230 * @throws UnsupportedOperationException if the {@code clear} operation
231 * is not supported by this list
232 */
233 public void clear() {
234 removeRange(0, size());
235 }
236
237 /**
238 * {@inheritDoc}
239 *
240 * <p>This implementation gets an iterator over the specified collection
241 * and iterates over it, inserting the elements obtained from the
242 * iterator into this list at the appropriate position, one at a time,
243 * using {@code add(int, E)}.
244 * Many implementations will override this method for efficiency.
245 *
246 * <p>Note that this implementation throws an
247 * {@code UnsupportedOperationException} unless
248 * {@link #add(int, Object) add(int, E)} is overridden.
249 *
250 * @throws UnsupportedOperationException {@inheritDoc}
251 * @throws ClassCastException {@inheritDoc}
252 * @throws NullPointerException {@inheritDoc}
253 * @throws IllegalArgumentException {@inheritDoc}
254 * @throws IndexOutOfBoundsException {@inheritDoc}
255 */
256 public boolean addAll(int index, Collection<? extends E> c) {
257 rangeCheckForAdd(index);
258 boolean modified = false;
259 Iterator<? extends E> e = c.iterator();
260 while (e.hasNext()) {
261 add(index++, e.next());
262 modified = true;
263 }
264 return modified;
265 }
266
267
268 // Iterators
269
270 /**
271 * Returns an iterator over the elements in this list in proper sequence.
272 *
273 * <p>This implementation returns a straightforward implementation of the
274 * iterator interface, relying on the backing list's {@code size()},
275 * {@code get(int)}, and {@code remove(int)} methods.
276 *
277 * <p>Note that the iterator returned by this method will throw an
278 * {@link UnsupportedOperationException} in response to its
279 * {@code remove} method unless the list's {@code remove(int)} method is
280 * overridden.
281 *
282 * <p>This implementation can be made to throw runtime exceptions in the
283 * face of concurrent modification, as described in the specification
284 * for the (protected) {@link #modCount} field.
285 *
286 * @return an iterator over the elements in this list in proper sequence
287 */
288 public Iterator<E> iterator() {
289 return new Itr();
290 }
291
292 /**
293 * {@inheritDoc}
294 *
295 * <p>This implementation returns {@code listIterator(0)}.
296 *
297 * @see #listIterator(int)
298 */
299 public ListIterator<E> listIterator() {
300 return listIterator(0);
301 }
302
303 /**
304 * {@inheritDoc}
305 *
306 * <p>This implementation returns a straightforward implementation of the
307 * {@code ListIterator} interface that extends the implementation of the
308 * {@code Iterator} interface returned by the {@code iterator()} method.
309 * The {@code ListIterator} implementation relies on the backing list's
310 * {@code get(int)}, {@code set(int, E)}, {@code add(int, E)}
311 * and {@code remove(int)} methods.
312 *
313 * <p>Note that the list iterator returned by this implementation will
314 * throw an {@link UnsupportedOperationException} in response to its
315 * {@code remove}, {@code set} and {@code add} methods unless the
316 * list's {@code remove(int)}, {@code set(int, E)}, and
317 * {@code add(int, E)} methods are overridden.
318 *
319 * <p>This implementation can be made to throw runtime exceptions in the
320 * face of concurrent modification, as described in the specification for
321 * the (protected) {@link #modCount} field.
322 *
323 * @throws IndexOutOfBoundsException {@inheritDoc}
324 */
325 public ListIterator<E> listIterator(final int index) {
326 rangeCheckForAdd(index);
327
328 return new ListItr(index);
329 }
330
331 private class Itr implements Iterator<E> {
332 /**
333 * Index of element to be returned by subsequent call to next.
334 */
335 int cursor = 0;
336
337 /**
338 * Index of element returned by most recent call to next or
339 * previous. Reset to -1 if this element is deleted by a call
340 * to remove.
341 */
342 int lastRet = -1;
343
344 /**
345 * The modCount value that the iterator believes that the backing
346 * List should have. If this expectation is violated, the iterator
347 * has detected concurrent modification.
348 */
349 int expectedModCount = modCount;
350
351 public boolean hasNext() {
352 return cursor != size();
353 }
354
355 public E next() {
356 checkForComodification();
357 try {
358 int i = cursor;
359 E next = get(i);
360 lastRet = i;
361 cursor = i + 1;
362 return next;
363 } catch (IndexOutOfBoundsException e) {
364 checkForComodification();
365 throw new NoSuchElementException();
366 }
367 }
368
369 public void remove() {
370 if (lastRet < 0)
371 throw new IllegalStateException();
372 checkForComodification();
373
374 try {
375 AbstractList.this.remove(lastRet);
376 if (lastRet < cursor)
377 cursor--;
378 lastRet = -1;
379 expectedModCount = modCount;
380 } catch (IndexOutOfBoundsException e) {
381 throw new ConcurrentModificationException();
382 }
383 }
384
385 final void checkForComodification() {
386 if (modCount != expectedModCount)
387 throw new ConcurrentModificationException();
388 }
389 }
390
391 private class ListItr extends Itr implements ListIterator<E> {
392 ListItr(int index) {
393 cursor = index;
394 }
395
396 public boolean hasPrevious() {
397 return cursor != 0;
398 }
399
400 public E previous() {
401 checkForComodification();
402 try {
403 int i = cursor - 1;
404 E previous = get(i);
405 lastRet = cursor = i;
406 return previous;
407 } catch (IndexOutOfBoundsException e) {
408 checkForComodification();
409 throw new NoSuchElementException();
410 }
411 }
412
413 public int nextIndex() {
414 return cursor;
415 }
416
417 public int previousIndex() {
418 return cursor-1;
419 }
420
421 public void set(E e) {
422 if (lastRet < 0)
423 throw new IllegalStateException();
424 checkForComodification();
425
426 try {
427 AbstractList.this.set(lastRet, e);
428 expectedModCount = modCount;
429 } catch (IndexOutOfBoundsException ex) {
430 throw new ConcurrentModificationException();
431 }
432 }
433
434 public void add(E e) {
435 checkForComodification();
436
437 try {
438 int i = cursor;
439 AbstractList.this.add(i, e);
440 lastRet = -1;
441 cursor = i + 1;
442 expectedModCount = modCount;
443 } catch (IndexOutOfBoundsException ex) {
444 throw new ConcurrentModificationException();
445 }
446 }
447 }
448
449 /**
450 * {@inheritDoc}
451 *
452 * <p>This implementation returns a list that subclasses
453 * {@code AbstractList}. The subclass stores, in private fields, the
454 * offset of the subList within the backing list, the size of the subList
455 * (which can change over its lifetime), and the expected
456 * {@code modCount} value of the backing list. There are two variants
457 * of the subclass, one of which implements {@code RandomAccess}.
458 * If this list implements {@code RandomAccess} the returned list will
459 * be an instance of the subclass that implements {@code RandomAccess}.
460 *
461 * <p>The subclass's {@code set(int, E)}, {@code get(int)},
462 * {@code add(int, E)}, {@code remove(int)}, {@code addAll(int,
463 * Collection)} and {@code removeRange(int, int)} methods all
464 * delegate to the corresponding methods on the backing abstract list,
465 * after bounds-checking the index and adjusting for the offset. The
466 * {@code addAll(Collection c)} method merely returns {@code addAll(size,
467 * c)}.
468 *
469 * <p>The {@code listIterator(int)} method returns a "wrapper object"
470 * over a list iterator on the backing list, which is created with the
471 * corresponding method on the backing list. The {@code iterator} method
472 * merely returns {@code listIterator()}, and the {@code size} method
473 * merely returns the subclass's {@code size} field.
474 *
475 * <p>All methods first check to see if the actual {@code modCount} of
476 * the backing list is equal to its expected value, and throw a
477 * {@code ConcurrentModificationException} if it is not.
478 *
479 * @throws IndexOutOfBoundsException if an endpoint index value is out of range
480 * {@code (fromIndex < 0 || toIndex > size)}
481 * @throws IllegalArgumentException if the endpoint indices are out of order
482 * {@code (fromIndex > toIndex)}
483 */
484 public List<E> subList(int fromIndex, int toIndex) {
485 return (this instanceof RandomAccess ?
486 new RandomAccessSubList<E>(this, fromIndex, toIndex) :
487 new SubList<E>(this, fromIndex, toIndex));
488 }
489
490 // Comparison and hashing
491
492 /**
493 * Compares the specified object with this list for equality. Returns
494 * {@code true} if and only if the specified object is also a list, both
495 * lists have the same size, and all corresponding pairs of elements in
496 * the two lists are <i>equal</i>. (Two elements {@code e1} and
497 * {@code e2} are <i>equal</i> if {@code (e1==null ? e2==null :
498 * e1.equals(e2))}.) In other words, two lists are defined to be
499 * equal if they contain the same elements in the same order.<p>
500 *
501 * This implementation first checks if the specified object is this
502 * list. If so, it returns {@code true}; if not, it checks if the
503 * specified object is a list. If not, it returns {@code false}; if so,
504 * it iterates over both lists, comparing corresponding pairs of elements.
505 * If any comparison returns {@code false}, this method returns
506 * {@code false}. If either iterator runs out of elements before the
507 * other it returns {@code false} (as the lists are of unequal length);
508 * otherwise it returns {@code true} when the iterations complete.
509 *
510 * @param o the object to be compared for equality with this list
511 * @return {@code true} if the specified object is equal to this list
512 */
513 public boolean equals(Object o) {
514 if (o == this)
515 return true;
516 if (!(o instanceof List))
517 return false;
518
519 ListIterator<E> e1 = listIterator();
520 ListIterator e2 = ((List) o).listIterator();
521 while(e1.hasNext() && e2.hasNext()) {
522 E o1 = e1.next();
523 Object o2 = e2.next();
524 if (!(o1==null ? o2==null : o1.equals(o2)))
525 return false;
526 }
527 return !(e1.hasNext() || e2.hasNext());
528 }
529
530 /**
531 * Returns the hash code value for this list.
532 *
533 * <p>This implementation uses exactly the code that is used to define the
534 * list hash function in the documentation for the {@link List#hashCode}
535 * method.
536 *
537 * @return the hash code value for this list
538 */
539 public int hashCode() {
540 int hashCode = 1;
541 for (E e : this)
542 hashCode = 31*hashCode + (e==null ? 0 : e.hashCode());
543 return hashCode;
544 }
545
546 /**
547 * Removes from this list all of the elements whose index is between
548 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
549 * Shifts any succeeding elements to the left (reduces their index).
550 * This call shortens the list by {@code (toIndex - fromIndex)} elements.
551 * (If {@code toIndex==fromIndex}, this operation has no effect.)
552 *
553 * <p>This method is called by the {@code clear} operation on this list
554 * and its subLists. Overriding this method to take advantage of
555 * the internals of the list implementation can <i>substantially</i>
556 * improve the performance of the {@code clear} operation on this list
557 * and its subLists.
558 *
559 * <p>This implementation gets a list iterator positioned before
560 * {@code fromIndex}, and repeatedly calls {@code ListIterator.next}
561 * followed by {@code ListIterator.remove} until the entire range has
562 * been removed. <b>Note: if {@code ListIterator.remove} requires linear
563 * time, this implementation requires quadratic time.</b>
564 *
565 * @param fromIndex index of first element to be removed
566 * @param toIndex index after last element to be removed
567 */
568 protected void removeRange(int fromIndex, int toIndex) {
569 ListIterator<E> it = listIterator(fromIndex);
570 for (int i=0, n=toIndex-fromIndex; i<n; i++) {
571 it.next();
572 it.remove();
573 }
574 }
575
576 /**
577 * The number of times this list has been <i>structurally modified</i>.
578 * Structural modifications are those that change the size of the
579 * list, or otherwise perturb it in such a fashion that iterations in
580 * progress may yield incorrect results.
581 *
582 * <p>This field is used by the iterator and list iterator implementation
583 * returned by the {@code iterator} and {@code listIterator} methods.
584 * If the value of this field changes unexpectedly, the iterator (or list
585 * iterator) will throw a {@code ConcurrentModificationException} in
586 * response to the {@code next}, {@code remove}, {@code previous},
587 * {@code set} or {@code add} operations. This provides
588 * <i>fail-fast</i> behavior, rather than non-deterministic behavior in
589 * the face of concurrent modification during iteration.
590 *
591 * <p><b>Use of this field by subclasses is optional.</b> If a subclass
592 * wishes to provide fail-fast iterators (and list iterators), then it
593 * merely has to increment this field in its {@code add(int, E)} and
594 * {@code remove(int)} methods (and any other methods that it overrides
595 * that result in structural modifications to the list). A single call to
596 * {@code add(int, E)} or {@code remove(int)} must add no more than
597 * one to this field, or the iterators (and list iterators) will throw
598 * bogus {@code ConcurrentModificationExceptions}. If an implementation
599 * does not wish to provide fail-fast iterators, this field may be
600 * ignored.
601 */
602 protected transient int modCount = 0;
603
604 private void rangeCheckForAdd(int index) {
605 if (index < 0 || index > size())
606 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
607 }
608
609 private String outOfBoundsMsg(int index) {
610 return "Index: "+index+", Size: "+size();
611 }
612 }
613
614 class SubList<E> extends AbstractList<E> {
615 private final AbstractList<E> l;
616 private final int offset;
617 private int size;
618
619 SubList(AbstractList<E> list, int fromIndex, int toIndex) {
620 if (fromIndex < 0)
621 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
622 if (toIndex > list.size())
623 throw new IndexOutOfBoundsException("toIndex = " + toIndex);
624 if (fromIndex > toIndex)
625 throw new IllegalArgumentException("fromIndex(" + fromIndex +
626 ") > toIndex(" + toIndex + ")");
627 l = list;
628 offset = fromIndex;
629 size = toIndex - fromIndex;
630 this.modCount = l.modCount;
631 }
632
633 public E set(int index, E element) {
634 rangeCheck(index);
635 checkForComodification();
636 return l.set(index+offset, element);
637 }
638
639 public E get(int index) {
640 rangeCheck(index);
641 checkForComodification();
642 return l.get(index+offset);
643 }
644
645 public int size() {
646 checkForComodification();
647 return size;
648 }
649
650 public void add(int index, E element) {
651 rangeCheckForAdd(index);
652 checkForComodification();
653 l.add(index+offset, element);
654 this.modCount = l.modCount;
655 size++;
656 }
657
658 public E remove(int index) {
659 rangeCheck(index);
660 checkForComodification();
661 E result = l.remove(index+offset);
662 this.modCount = l.modCount;
663 size--;
664 return result;
665 }
666
667 protected void removeRange(int fromIndex, int toIndex) {
668 checkForComodification();
669 l.removeRange(fromIndex+offset, toIndex+offset);
670 this.modCount = l.modCount;
671 size -= (toIndex-fromIndex);
672 }
673
674 public boolean addAll(Collection<? extends E> c) {
675 return addAll(size, c);
676 }
677
678 public boolean addAll(int index, Collection<? extends E> c) {
679 rangeCheckForAdd(index);
680 int cSize = c.size();
681 if (cSize==0)
682 return false;
683
684 checkForComodification();
685 l.addAll(offset+index, c);
686 this.modCount = l.modCount;
687 size += cSize;
688 return true;
689 }
690
691 public Iterator<E> iterator() {
692 return listIterator();
693 }
694
695 public ListIterator<E> listIterator(final int index) {
696 checkForComodification();
697 rangeCheckForAdd(index);
698
699 return new ListIterator<E>() {
700 private final ListIterator<E> i = l.listIterator(index+offset);
701
702 public boolean hasNext() {
703 return nextIndex() < size;
704 }
705
706 public E next() {
707 if (hasNext())
708 return i.next();
709 else
710 throw new NoSuchElementException();
711 }
712
713 public boolean hasPrevious() {
714 return previousIndex() >= 0;
715 }
716
717 public E previous() {
718 if (hasPrevious())
719 return i.previous();
720 else
721 throw new NoSuchElementException();
722 }
723
724 public int nextIndex() {
725 return i.nextIndex() - offset;
726 }
727
728 public int previousIndex() {
729 return i.previousIndex() - offset;
730 }
731
732 public void remove() {
733 i.remove();
734 SubList.this.modCount = l.modCount;
735 size--;
736 }
737
738 public void set(E e) {
739 i.set(e);
740 }
741
742 public void add(E e) {
743 i.add(e);
744 SubList.this.modCount = l.modCount;
745 size++;
746 }
747 };
748 }
749
750 public List<E> subList(int fromIndex, int toIndex) {
751 return new SubList<E>(this, fromIndex, toIndex);
752 }
753
754 private void rangeCheck(int index) {
755 if (index < 0 || index >= size)
756 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
757 }
758
759 private void rangeCheckForAdd(int index) {
760 if (index < 0 || index > size)
761 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
762 }
763
764 private String outOfBoundsMsg(int index) {
765 return "Index: "+index+", Size: "+size;
766 }
767
768 private void checkForComodification() {
769 if (this.modCount != l.modCount)
770 throw new ConcurrentModificationException();
771 }
772 }
773
774 class RandomAccessSubList<E> extends SubList<E> implements RandomAccess {
775 RandomAccessSubList(AbstractList<E> list, int fromIndex, int toIndex) {
776 super(list, fromIndex, toIndex);
777 }
778
779 public List<E> subList(int fromIndex, int toIndex) {
780 return new RandomAccessSubList<E>(this, fromIndex, toIndex);
781 }
782 }
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