1 /*
2 * Copyright (c) 1994, 2011, 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
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7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
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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).
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24 */
25
26 package java.util;
27
28 /**
29 * The {@code Vector} class implements a growable array of
30 * objects. Like an array, it contains components that can be
31 * accessed using an integer index. However, the size of a
32 * {@code Vector} can grow or shrink as needed to accommodate
33 * adding and removing items after the {@code Vector} has been created.
34 *
35 * <p>Each vector tries to optimize storage management by maintaining a
36 * {@code capacity} and a {@code capacityIncrement}. The
37 * {@code capacity} is always at least as large as the vector
38 * size; it is usually larger because as components are added to the
39 * vector, the vector's storage increases in chunks the size of
40 * {@code capacityIncrement}. An application can increase the
41 * capacity of a vector before inserting a large number of
42 * components; this reduces the amount of incremental reallocation.
43 *
44 * <p><a name="fail-fast"/>
45 * The iterators returned by this class's {@link #iterator() iterator} and
46 * {@link #listIterator(int) listIterator} methods are <em>fail-fast</em>:
47 * if the vector is structurally modified at any time after the iterator is
48 * created, in any way except through the iterator's own
49 * {@link ListIterator#remove() remove} or
50 * {@link ListIterator#add(Object) add} methods, the iterator will throw a
51 * {@link ConcurrentModificationException}. Thus, in the face of
52 * concurrent modification, the iterator fails quickly and cleanly, rather
53 * than risking arbitrary, non-deterministic behavior at an undetermined
54 * time in the future. The {@link Enumeration Enumerations} returned by
55 * the {@link #elements() elements} method are <em>not</em> fail-fast.
56 *
57 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
58 * as it is, generally speaking, impossible to make any hard guarantees in the
59 * presence of unsynchronized concurrent modification. Fail-fast iterators
60 * throw {@code ConcurrentModificationException} on a best-effort basis.
61 * Therefore, it would be wrong to write a program that depended on this
62 * exception for its correctness: <i>the fail-fast behavior of iterators
63 * should be used only to detect bugs.</i>
64 *
65 * <p>As of the Java 2 platform v1.2, this class was retrofitted to
66 * implement the {@link List} interface, making it a member of the
67 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
68 * Java Collections Framework</a>. Unlike the new collection
69 * implementations, {@code Vector} is synchronized. If a thread-safe
70 * implementation is not needed, it is recommended to use {@link
71 * ArrayList} in place of {@code Vector}.
72 *
73 * @author Lee Boynton
74 * @author Jonathan Payne
75 * @see Collection
76 * @see LinkedList
77 * @since JDK1.0
78 */
79 public class Vector<E>
80 extends AbstractList<E>
81 implements List<E>, RandomAccess, Cloneable, java.io.Serializable
82 {
83 /**
84 * The array buffer into which the components of the vector are
85 * stored. The capacity of the vector is the length of this array buffer,
86 * and is at least large enough to contain all the vector's elements.
87 *
88 * <p>Any array elements following the last element in the Vector are null.
89 *
90 * @serial
91 */
92 protected Object[] elementData;
93
94 /**
95 * The number of valid components in this {@code Vector} object.
96 * Components {@code elementData[0]} through
97 * {@code elementData[elementCount-1]} are the actual items.
98 *
99 * @serial
100 */
101 protected int elementCount;
102
103 /**
104 * The amount by which the capacity of the vector is automatically
105 * incremented when its size becomes greater than its capacity. If
106 * the capacity increment is less than or equal to zero, the capacity
107 * of the vector is doubled each time it needs to grow.
108 *
109 * @serial
110 */
111 protected int capacityIncrement;
112
113 /** use serialVersionUID from JDK 1.0.2 for interoperability */
114 private static final long serialVersionUID = -2767605614048989439L;
115
116 /**
117 * Constructs an empty vector with the specified initial capacity and
118 * capacity increment.
119 *
120 * @param initialCapacity the initial capacity of the vector
121 * @param capacityIncrement the amount by which the capacity is
122 * increased when the vector overflows
123 * @throws IllegalArgumentException if the specified initial capacity
124 * is negative
125 */
126 public Vector(int initialCapacity, int capacityIncrement) {
127 super();
128 if (initialCapacity < 0)
129 throw new IllegalArgumentException("Illegal Capacity: "+
130 initialCapacity);
131 this.elementData = new Object[initialCapacity];
132 this.capacityIncrement = capacityIncrement;
133 }
134
135 /**
136 * Constructs an empty vector with the specified initial capacity and
137 * with its capacity increment equal to zero.
138 *
139 * @param initialCapacity the initial capacity of the vector
140 * @throws IllegalArgumentException if the specified initial capacity
141 * is negative
142 */
143 public Vector(int initialCapacity) {
144 this(initialCapacity, 0);
145 }
146
147 /**
148 * Constructs an empty vector so that its internal data array
149 * has size {@code 10} and its standard capacity increment is
150 * zero.
151 */
152 public Vector() {
153 this(10);
154 }
155
156 /**
157 * Constructs a vector containing the elements of the specified
158 * collection, in the order they are returned by the collection's
159 * iterator.
160 *
161 * @param c the collection whose elements are to be placed into this
162 * vector
163 * @throws NullPointerException if the specified collection is null
164 * @since 1.2
165 */
166 public Vector(Collection<? extends E> c) {
167 elementData = c.toArray();
168 elementCount = elementData.length;
169 // c.toArray might (incorrectly) not return Object[] (see 6260652)
170 if (elementData.getClass() != Object[].class)
171 elementData = Arrays.copyOf(elementData, elementCount, Object[].class);
172 }
173
174 /**
175 * Copies the components of this vector into the specified array.
176 * The item at index {@code k} in this vector is copied into
177 * component {@code k} of {@code anArray}.
178 *
179 * @param anArray the array into which the components get copied
180 * @throws NullPointerException if the given array is null
181 * @throws IndexOutOfBoundsException if the specified array is not
182 * large enough to hold all the components of this vector
183 * @throws ArrayStoreException if a component of this vector is not of
184 * a runtime type that can be stored in the specified array
185 * @see #toArray(Object[])
186 */
187 public synchronized void copyInto(Object[] anArray) {
188 System.arraycopy(elementData, 0, anArray, 0, elementCount);
189 }
190
191 /**
192 * Trims the capacity of this vector to be the vector's current
193 * size. If the capacity of this vector is larger than its current
194 * size, then the capacity is changed to equal the size by replacing
195 * its internal data array, kept in the field {@code elementData},
196 * with a smaller one. An application can use this operation to
197 * minimize the storage of a vector.
198 */
199 public synchronized void trimToSize() {
200 modCount++;
201 int oldCapacity = elementData.length;
202 if (elementCount < oldCapacity) {
203 elementData = Arrays.copyOf(elementData, elementCount);
204 }
205 }
206
207 /**
208 * Increases the capacity of this vector, if necessary, to ensure
209 * that it can hold at least the number of components specified by
210 * the minimum capacity argument.
211 *
212 * <p>If the current capacity of this vector is less than
213 * {@code minCapacity}, then its capacity is increased by replacing its
214 * internal data array, kept in the field {@code elementData}, with a
215 * larger one. The size of the new data array will be the old size plus
216 * {@code capacityIncrement}, unless the value of
217 * {@code capacityIncrement} is less than or equal to zero, in which case
218 * the new capacity will be twice the old capacity; but if this new size
219 * is still smaller than {@code minCapacity}, then the new capacity will
220 * be {@code minCapacity}.
221 *
222 * @param minCapacity the desired minimum capacity
223 */
224 public synchronized void ensureCapacity(int minCapacity) {
225 if (minCapacity > 0) {
226 modCount++;
227 ensureCapacityHelper(minCapacity);
228 }
229 }
230
231 /**
232 * This implements the unsynchronized semantics of ensureCapacity.
233 * Synchronized methods in this class can internally call this
234 * method for ensuring capacity without incurring the cost of an
235 * extra synchronization.
236 *
237 * @see #ensureCapacity(int)
238 */
239 private void ensureCapacityHelper(int minCapacity) {
240 // overflow-conscious code
241 if (minCapacity - elementData.length > 0)
242 grow(minCapacity);
243 }
244
245 /**
246 * The maximum size of array to allocate.
247 * Some VMs reserve some header words in an array.
248 * Attempts to allocate larger arrays may result in
249 * OutOfMemoryError: Requested array size exceeds VM limit
250 */
251 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
252
253 private void grow(int minCapacity) {
254 // overflow-conscious code
255 int oldCapacity = elementData.length;
256 int newCapacity = oldCapacity + ((capacityIncrement > 0) ?
257 capacityIncrement : oldCapacity);
258 if (newCapacity - minCapacity < 0)
259 newCapacity = minCapacity;
260 if (newCapacity - MAX_ARRAY_SIZE > 0)
261 newCapacity = hugeCapacity(minCapacity);
262 elementData = Arrays.copyOf(elementData, newCapacity);
263 }
264
265 private static int hugeCapacity(int minCapacity) {
266 if (minCapacity < 0) // overflow
267 throw new OutOfMemoryError();
268 return (minCapacity > MAX_ARRAY_SIZE) ?
269 Integer.MAX_VALUE :
270 MAX_ARRAY_SIZE;
271 }
272
273 /**
274 * Sets the size of this vector. If the new size is greater than the
275 * current size, new {@code null} items are added to the end of
276 * the vector. If the new size is less than the current size, all
277 * components at index {@code newSize} and greater are discarded.
278 *
279 * @param newSize the new size of this vector
280 * @throws ArrayIndexOutOfBoundsException if the new size is negative
281 */
282 public synchronized void setSize(int newSize) {
283 modCount++;
284 if (newSize > elementCount) {
285 ensureCapacityHelper(newSize);
286 } else {
287 for (int i = newSize ; i < elementCount ; i++) {
288 elementData[i] = null;
289 }
290 }
291 elementCount = newSize;
292 }
293
294 /**
295 * Returns the current capacity of this vector.
296 *
297 * @return the current capacity (the length of its internal
298 * data array, kept in the field {@code elementData}
299 * of this vector)
300 */
301 public synchronized int capacity() {
302 return elementData.length;
303 }
304
305 /**
306 * Returns the number of components in this vector.
307 *
308 * @return the number of components in this vector
309 */
310 public synchronized int size() {
311 return elementCount;
312 }
313
314 /**
315 * Tests if this vector has no components.
316 *
317 * @return {@code true} if and only if this vector has
318 * no components, that is, its size is zero;
319 * {@code false} otherwise.
320 */
321 public synchronized boolean isEmpty() {
322 return elementCount == 0;
323 }
324
325 /**
326 * Returns an enumeration of the components of this vector. The
327 * returned {@code Enumeration} object will generate all items in
328 * this vector. The first item generated is the item at index {@code 0},
329 * then the item at index {@code 1}, and so on.
330 *
331 * @return an enumeration of the components of this vector
332 * @see Iterator
333 */
334 public Enumeration<E> elements() {
335 return new Enumeration<E>() {
336 int count = 0;
337
338 public boolean hasMoreElements() {
339 return count < elementCount;
340 }
341
342 public E nextElement() {
343 synchronized (Vector.this) {
344 if (count < elementCount) {
345 return elementData(count++);
346 }
347 }
348 throw new NoSuchElementException("Vector Enumeration");
349 }
350 };
351 }
352
353 /**
354 * Returns {@code true} if this vector contains the specified element.
355 * More formally, returns {@code true} if and only if this vector
356 * contains at least one element {@code e} such that
357 * <tt>(o==null ? e==null : o.equals(e))</tt>.
358 *
359 * @param o element whose presence in this vector is to be tested
360 * @return {@code true} if this vector contains the specified element
361 */
362 public boolean contains(Object o) {
363 return indexOf(o, 0) >= 0;
364 }
365
366 /**
367 * Returns the index of the first occurrence of the specified element
368 * in this vector, or -1 if this vector does not contain the element.
369 * More formally, returns the lowest index {@code i} such that
370 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
371 * or -1 if there is no such index.
372 *
373 * @param o element to search for
374 * @return the index of the first occurrence of the specified element in
375 * this vector, or -1 if this vector does not contain the element
376 */
377 public int indexOf(Object o) {
378 return indexOf(o, 0);
379 }
380
381 /**
382 * Returns the index of the first occurrence of the specified element in
383 * this vector, searching forwards from {@code index}, or returns -1 if
384 * the element is not found.
385 * More formally, returns the lowest index {@code i} such that
386 * <tt>(i >= index && (o==null ? get(i)==null : o.equals(get(i))))</tt>,
387 * or -1 if there is no such index.
388 *
389 * @param o element to search for
390 * @param index index to start searching from
391 * @return the index of the first occurrence of the element in
392 * this vector at position {@code index} or later in the vector;
393 * {@code -1} if the element is not found.
394 * @throws IndexOutOfBoundsException if the specified index is negative
395 * @see Object#equals(Object)
396 */
397 public synchronized int indexOf(Object o, int index) {
398 if (o == null) {
399 for (int i = index ; i < elementCount ; i++)
400 if (elementData[i]==null)
401 return i;
402 } else {
403 for (int i = index ; i < elementCount ; i++)
404 if (o.equals(elementData[i]))
405 return i;
406 }
407 return -1;
408 }
409
410 /**
411 * Returns the index of the last occurrence of the specified element
412 * in this vector, or -1 if this vector does not contain the element.
413 * More formally, returns the highest index {@code i} such that
414 * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
415 * or -1 if there is no such index.
416 *
417 * @param o element to search for
418 * @return the index of the last occurrence of the specified element in
419 * this vector, or -1 if this vector does not contain the element
420 */
421 public synchronized int lastIndexOf(Object o) {
422 return lastIndexOf(o, elementCount-1);
423 }
424
425 /**
426 * Returns the index of the last occurrence of the specified element in
427 * this vector, searching backwards from {@code index}, or returns -1 if
428 * the element is not found.
429 * More formally, returns the highest index {@code i} such that
430 * <tt>(i <= index && (o==null ? get(i)==null : o.equals(get(i))))</tt>,
431 * or -1 if there is no such index.
432 *
433 * @param o element to search for
434 * @param index index to start searching backwards from
435 * @return the index of the last occurrence of the element at position
436 * less than or equal to {@code index} in this vector;
437 * -1 if the element is not found.
438 * @throws IndexOutOfBoundsException if the specified index is greater
439 * than or equal to the current size of this vector
440 */
441 public synchronized int lastIndexOf(Object o, int index) {
442 if (index >= elementCount)
443 throw new IndexOutOfBoundsException(index + " >= "+ elementCount);
444
445 if (o == null) {
446 for (int i = index; i >= 0; i--)
447 if (elementData[i]==null)
448 return i;
449 } else {
450 for (int i = index; i >= 0; i--)
451 if (o.equals(elementData[i]))
452 return i;
453 }
454 return -1;
455 }
456
457 /**
458 * Returns the component at the specified index.
459 *
460 * <p>This method is identical in functionality to the {@link #get(int)}
461 * method (which is part of the {@link List} interface).
462 *
463 * @param index an index into this vector
464 * @return the component at the specified index
465 * @throws ArrayIndexOutOfBoundsException if the index is out of range
466 * ({@code index < 0 || index >= size()})
467 */
468 public synchronized E elementAt(int index) {
469 if (index >= elementCount) {
470 throw new ArrayIndexOutOfBoundsException(index + " >= " + elementCount);
471 }
472
473 return elementData(index);
474 }
475
476 /**
477 * Returns the first component (the item at index {@code 0}) of
478 * this vector.
479 *
480 * @return the first component of this vector
481 * @throws NoSuchElementException if this vector has no components
482 */
483 public synchronized E firstElement() {
484 if (elementCount == 0) {
485 throw new NoSuchElementException();
486 }
487 return elementData(0);
488 }
489
490 /**
491 * Returns the last component of the vector.
492 *
493 * @return the last component of the vector, i.e., the component at index
494 * <code>size() - 1</code>.
495 * @throws NoSuchElementException if this vector is empty
496 */
497 public synchronized E lastElement() {
498 if (elementCount == 0) {
499 throw new NoSuchElementException();
500 }
501 return elementData(elementCount - 1);
502 }
503
504 /**
505 * Sets the component at the specified {@code index} of this
506 * vector to be the specified object. The previous component at that
507 * position is discarded.
508 *
509 * <p>The index must be a value greater than or equal to {@code 0}
510 * and less than the current size of the vector.
511 *
512 * <p>This method is identical in functionality to the
513 * {@link #set(int, Object) set(int, E)}
514 * method (which is part of the {@link List} interface). Note that the
515 * {@code set} method reverses the order of the parameters, to more closely
516 * match array usage. Note also that the {@code set} method returns the
517 * old value that was stored at the specified position.
518 *
519 * @param obj what the component is to be set to
520 * @param index the specified index
521 * @throws ArrayIndexOutOfBoundsException if the index is out of range
522 * ({@code index < 0 || index >= size()})
523 */
524 public synchronized void setElementAt(E obj, int index) {
525 if (index >= elementCount) {
526 throw new ArrayIndexOutOfBoundsException(index + " >= " +
527 elementCount);
528 }
529 elementData[index] = obj;
530 }
531
532 /**
533 * Deletes the component at the specified index. Each component in
534 * this vector with an index greater or equal to the specified
535 * {@code index} is shifted downward to have an index one
536 * smaller than the value it had previously. The size of this vector
537 * is decreased by {@code 1}.
538 *
539 * <p>The index must be a value greater than or equal to {@code 0}
540 * and less than the current size of the vector.
541 *
542 * <p>This method is identical in functionality to the {@link #remove(int)}
543 * method (which is part of the {@link List} interface). Note that the
544 * {@code remove} method returns the old value that was stored at the
545 * specified position.
546 *
547 * @param index the index of the object to remove
548 * @throws ArrayIndexOutOfBoundsException if the index is out of range
549 * ({@code index < 0 || index >= size()})
550 */
551 public synchronized void removeElementAt(int index) {
552 modCount++;
553 if (index >= elementCount) {
554 throw new ArrayIndexOutOfBoundsException(index + " >= " +
555 elementCount);
556 }
557 else if (index < 0) {
558 throw new ArrayIndexOutOfBoundsException(index);
559 }
560 int j = elementCount - index - 1;
561 if (j > 0) {
562 System.arraycopy(elementData, index + 1, elementData, index, j);
563 }
564 elementCount--;
565 elementData[elementCount] = null; /* to let gc do its work */
566 }
567
568 /**
569 * Inserts the specified object as a component in this vector at the
570 * specified {@code index}. Each component in this vector with
571 * an index greater or equal to the specified {@code index} is
572 * shifted upward to have an index one greater than the value it had
573 * previously.
574 *
575 * <p>The index must be a value greater than or equal to {@code 0}
576 * and less than or equal to the current size of the vector. (If the
577 * index is equal to the current size of the vector, the new element
578 * is appended to the Vector.)
579 *
580 * <p>This method is identical in functionality to the
581 * {@link #add(int, Object) add(int, E)}
582 * method (which is part of the {@link List} interface). Note that the
583 * {@code add} method reverses the order of the parameters, to more closely
584 * match array usage.
585 *
586 * @param obj the component to insert
587 * @param index where to insert the new component
588 * @throws ArrayIndexOutOfBoundsException if the index is out of range
589 * ({@code index < 0 || index > size()})
590 */
591 public synchronized void insertElementAt(E obj, int index) {
592 modCount++;
593 if (index > elementCount) {
594 throw new ArrayIndexOutOfBoundsException(index
595 + " > " + elementCount);
596 }
597 ensureCapacityHelper(elementCount + 1);
598 System.arraycopy(elementData, index, elementData, index + 1, elementCount - index);
599 elementData[index] = obj;
600 elementCount++;
601 }
602
603 /**
604 * Adds the specified component to the end of this vector,
605 * increasing its size by one. The capacity of this vector is
606 * increased if its size becomes greater than its capacity.
607 *
608 * <p>This method is identical in functionality to the
609 * {@link #add(Object) add(E)}
610 * method (which is part of the {@link List} interface).
611 *
612 * @param obj the component to be added
613 */
614 public synchronized void addElement(E obj) {
615 modCount++;
616 ensureCapacityHelper(elementCount + 1);
617 elementData[elementCount++] = obj;
618 }
619
620 /**
621 * Removes the first (lowest-indexed) occurrence of the argument
622 * from this vector. If the object is found in this vector, each
623 * component in the vector with an index greater or equal to the
624 * object's index is shifted downward to have an index one smaller
625 * than the value it had previously.
626 *
627 * <p>This method is identical in functionality to the
628 * {@link #remove(Object)} method (which is part of the
629 * {@link List} interface).
630 *
631 * @param obj the component to be removed
632 * @return {@code true} if the argument was a component of this
633 * vector; {@code false} otherwise.
634 */
635 public synchronized boolean removeElement(Object obj) {
636 modCount++;
637 int i = indexOf(obj);
638 if (i >= 0) {
639 removeElementAt(i);
640 return true;
641 }
642 return false;
643 }
644
645 /**
646 * Removes all components from this vector and sets its size to zero.
647 *
648 * <p>This method is identical in functionality to the {@link #clear}
649 * method (which is part of the {@link List} interface).
650 */
651 public synchronized void removeAllElements() {
652 modCount++;
653 // Let gc do its work
654 for (int i = 0; i < elementCount; i++)
655 elementData[i] = null;
656
657 elementCount = 0;
658 }
659
660 /**
661 * Returns a clone of this vector. The copy will contain a
662 * reference to a clone of the internal data array, not a reference
663 * to the original internal data array of this {@code Vector} object.
664 *
665 * @return a clone of this vector
666 */
667 public synchronized Object clone() {
668 try {
669 @SuppressWarnings("unchecked")
670 Vector<E> v = (Vector<E>) super.clone();
671 v.elementData = Arrays.copyOf(elementData, elementCount);
672 v.modCount = 0;
673 return v;
674 } catch (CloneNotSupportedException e) {
675 // this shouldn't happen, since we are Cloneable
676 throw new InternalError();
677 }
678 }
679
680 /**
681 * Returns an array containing all of the elements in this Vector
682 * in the correct order.
683 *
684 * @since 1.2
685 */
686 public synchronized Object[] toArray() {
687 return Arrays.copyOf(elementData, elementCount);
688 }
689
690 /**
691 * Returns an array containing all of the elements in this Vector in the
692 * correct order; the runtime type of the returned array is that of the
693 * specified array. If the Vector fits in the specified array, it is
694 * returned therein. Otherwise, a new array is allocated with the runtime
695 * type of the specified array and the size of this Vector.
696 *
697 * <p>If the Vector fits in the specified array with room to spare
698 * (i.e., the array has more elements than the Vector),
699 * the element in the array immediately following the end of the
700 * Vector is set to null. (This is useful in determining the length
701 * of the Vector <em>only</em> if the caller knows that the Vector
702 * does not contain any null elements.)
703 *
704 * @param a the array into which the elements of the Vector are to
705 * be stored, if it is big enough; otherwise, a new array of the
706 * same runtime type is allocated for this purpose.
707 * @return an array containing the elements of the Vector
708 * @throws ArrayStoreException if the runtime type of a is not a supertype
709 * of the runtime type of every element in this Vector
710 * @throws NullPointerException if the given array is null
711 * @since 1.2
712 */
713 @SuppressWarnings("unchecked")
714 public synchronized <T> T[] toArray(T[] a) {
715 if (a.length < elementCount)
716 return (T[]) Arrays.copyOf(elementData, elementCount, a.getClass());
717
718 System.arraycopy(elementData, 0, a, 0, elementCount);
719
720 if (a.length > elementCount)
721 a[elementCount] = null;
722
723 return a;
724 }
725
726 // Positional Access Operations
727
728 @SuppressWarnings("unchecked")
729 E elementData(int index) {
730 return (E) elementData[index];
731 }
732
733 /**
734 * Returns the element at the specified position in this Vector.
735 *
736 * @param index index of the element to return
737 * @return object at the specified index
738 * @throws ArrayIndexOutOfBoundsException if the index is out of range
739 * ({@code index < 0 || index >= size()})
740 * @since 1.2
741 */
742 public synchronized E get(int index) {
743 if (index >= elementCount)
744 throw new ArrayIndexOutOfBoundsException(index);
745
746 return elementData(index);
747 }
748
749 /**
750 * Replaces the element at the specified position in this Vector with the
751 * specified element.
752 *
753 * @param index index of the element to replace
754 * @param element element to be stored at the specified position
755 * @return the element previously at the specified position
756 * @throws ArrayIndexOutOfBoundsException if the index is out of range
757 * ({@code index < 0 || index >= size()})
758 * @since 1.2
759 */
760 public synchronized E set(int index, E element) {
761 if (index >= elementCount)
762 throw new ArrayIndexOutOfBoundsException(index);
763
764 E oldValue = elementData(index);
765 elementData[index] = element;
766 return oldValue;
767 }
768
769 /**
770 * Appends the specified element to the end of this Vector.
771 *
772 * @param e element to be appended to this Vector
773 * @return {@code true} (as specified by {@link Collection#add})
774 * @since 1.2
775 */
776 public synchronized boolean add(E e) {
777 modCount++;
778 ensureCapacityHelper(elementCount + 1);
779 elementData[elementCount++] = e;
780 return true;
781 }
782
783 /**
784 * Removes the first occurrence of the specified element in this Vector
785 * If the Vector does not contain the element, it is unchanged. More
786 * formally, removes the element with the lowest index i such that
787 * {@code (o==null ? get(i)==null : o.equals(get(i)))} (if such
788 * an element exists).
789 *
790 * @param o element to be removed from this Vector, if present
791 * @return true if the Vector contained the specified element
792 * @since 1.2
793 */
794 public boolean remove(Object o) {
795 return removeElement(o);
796 }
797
798 /**
799 * Inserts the specified element at the specified position in this Vector.
800 * Shifts the element currently at that position (if any) and any
801 * subsequent elements to the right (adds one to their indices).
802 *
803 * @param index index at which the specified element is to be inserted
804 * @param element element to be inserted
805 * @throws ArrayIndexOutOfBoundsException if the index is out of range
806 * ({@code index < 0 || index > size()})
807 * @since 1.2
808 */
809 public void add(int index, E element) {
810 insertElementAt(element, index);
811 }
812
813 /**
814 * Removes the element at the specified position in this Vector.
815 * Shifts any subsequent elements to the left (subtracts one from their
816 * indices). Returns the element that was removed from the Vector.
817 *
818 * @throws ArrayIndexOutOfBoundsException if the index is out of range
819 * ({@code index < 0 || index >= size()})
820 * @param index the index of the element to be removed
821 * @return element that was removed
822 * @since 1.2
823 */
824 public synchronized E remove(int index) {
825 modCount++;
826 if (index >= elementCount)
827 throw new ArrayIndexOutOfBoundsException(index);
828 E oldValue = elementData(index);
829
830 int numMoved = elementCount - index - 1;
831 if (numMoved > 0)
832 System.arraycopy(elementData, index+1, elementData, index,
833 numMoved);
834 elementData[--elementCount] = null; // Let gc do its work
835
836 return oldValue;
837 }
838
839 /**
840 * Removes all of the elements from this Vector. The Vector will
841 * be empty after this call returns (unless it throws an exception).
842 *
843 * @since 1.2
844 */
845 public void clear() {
846 removeAllElements();
847 }
848
849 // Bulk Operations
850
851 /**
852 * Returns true if this Vector contains all of the elements in the
853 * specified Collection.
854 *
855 * @param c a collection whose elements will be tested for containment
856 * in this Vector
857 * @return true if this Vector contains all of the elements in the
858 * specified collection
859 * @throws NullPointerException if the specified collection is null
860 */
861 public synchronized boolean containsAll(Collection<?> c) {
862 return super.containsAll(c);
863 }
864
865 /**
866 * Appends all of the elements in the specified Collection to the end of
867 * this Vector, in the order that they are returned by the specified
868 * Collection's Iterator. The behavior of this operation is undefined if
869 * the specified Collection is modified while the operation is in progress.
870 * (This implies that the behavior of this call is undefined if the
871 * specified Collection is this Vector, and this Vector is nonempty.)
872 *
873 * @param c elements to be inserted into this Vector
874 * @return {@code true} if this Vector changed as a result of the call
875 * @throws NullPointerException if the specified collection is null
876 * @since 1.2
877 */
878 public synchronized boolean addAll(Collection<? extends E> c) {
879 modCount++;
880 Object[] a = c.toArray();
881 int numNew = a.length;
882 ensureCapacityHelper(elementCount + numNew);
883 System.arraycopy(a, 0, elementData, elementCount, numNew);
884 elementCount += numNew;
885 return numNew != 0;
886 }
887
888 /**
889 * Removes from this Vector all of its elements that are contained in the
890 * specified Collection.
891 *
892 * @param c a collection of elements to be removed from the Vector
893 * @return true if this Vector changed as a result of the call
894 * @throws ClassCastException if the types of one or more elements
895 * in this vector are incompatible with the specified
896 * collection
897 * (<a href="Collection.html#optional-restrictions">optional</a>)
898 * @throws NullPointerException if this vector contains one or more null
899 * elements and the specified collection does not support null
900 * elements
901 * (<a href="Collection.html#optional-restrictions">optional</a>),
902 * or if the specified collection is null
903 * @since 1.2
904 */
905 public synchronized boolean removeAll(Collection<?> c) {
906 return super.removeAll(c);
907 }
908
909 /**
910 * Retains only the elements in this Vector that are contained in the
911 * specified Collection. In other words, removes from this Vector all
912 * of its elements that are not contained in the specified Collection.
913 *
914 * @param c a collection of elements to be retained in this Vector
915 * (all other elements are removed)
916 * @return true if this Vector changed as a result of the call
917 * @throws ClassCastException if the types of one or more elements
918 * in this vector are incompatible with the specified
919 * collection
920 * (<a href="Collection.html#optional-restrictions">optional</a>)
921 * @throws NullPointerException if this vector contains one or more null
922 * elements and the specified collection does not support null
923 * elements
924 * (<a href="Collection.html#optional-restrictions">optional</a>),
925 * or if the specified collection is null
926 * @since 1.2
927 */
928 public synchronized boolean retainAll(Collection<?> c) {
929 return super.retainAll(c);
930 }
931
932 /**
933 * Inserts all of the elements in the specified Collection into this
934 * Vector at the specified position. Shifts the element currently at
935 * that position (if any) and any subsequent elements to the right
936 * (increases their indices). The new elements will appear in the Vector
937 * in the order that they are returned by the specified Collection's
938 * iterator.
939 *
940 * @param index index at which to insert the first element from the
941 * specified collection
942 * @param c elements to be inserted into this Vector
943 * @return {@code true} if this Vector changed as a result of the call
944 * @throws ArrayIndexOutOfBoundsException if the index is out of range
945 * ({@code index < 0 || index > size()})
946 * @throws NullPointerException if the specified collection is null
947 * @since 1.2
948 */
949 public synchronized boolean addAll(int index, Collection<? extends E> c) {
950 modCount++;
951 if (index < 0 || index > elementCount)
952 throw new ArrayIndexOutOfBoundsException(index);
953
954 Object[] a = c.toArray();
955 int numNew = a.length;
956 ensureCapacityHelper(elementCount + numNew);
957
958 int numMoved = elementCount - index;
959 if (numMoved > 0)
960 System.arraycopy(elementData, index, elementData, index + numNew,
961 numMoved);
962
963 System.arraycopy(a, 0, elementData, index, numNew);
964 elementCount += numNew;
965 return numNew != 0;
966 }
967
968 /**
969 * Compares the specified Object with this Vector for equality. Returns
970 * true if and only if the specified Object is also a List, both Lists
971 * have the same size, and all corresponding pairs of elements in the two
972 * Lists are <em>equal</em>. (Two elements {@code e1} and
973 * {@code e2} are <em>equal</em> if {@code (e1==null ? e2==null :
974 * e1.equals(e2))}.) In other words, two Lists are defined to be
975 * equal if they contain the same elements in the same order.
976 *
977 * @param o the Object to be compared for equality with this Vector
978 * @return true if the specified Object is equal to this Vector
979 */
980 public synchronized boolean equals(Object o) {
981 return super.equals(o);
982 }
983
984 /**
985 * Returns the hash code value for this Vector.
986 */
987 public synchronized int hashCode() {
988 return super.hashCode();
989 }
990
991 /**
992 * Returns a string representation of this Vector, containing
993 * the String representation of each element.
994 */
995 public synchronized String toString() {
996 return super.toString();
997 }
998
999 /**
1000 * Returns a view of the portion of this List between fromIndex,
1001 * inclusive, and toIndex, exclusive. (If fromIndex and toIndex are
1002 * equal, the returned List is empty.) The returned List is backed by this
1003 * List, so changes in the returned List are reflected in this List, and
1004 * vice-versa. The returned List supports all of the optional List
1005 * operations supported by this List.
1006 *
1007 * <p>This method eliminates the need for explicit range operations (of
1008 * the sort that commonly exist for arrays). Any operation that expects
1009 * a List can be used as a range operation by operating on a subList view
1010 * instead of a whole List. For example, the following idiom
1011 * removes a range of elements from a List:
1012 * <pre>
1013 * list.subList(from, to).clear();
1014 * </pre>
1015 * Similar idioms may be constructed for indexOf and lastIndexOf,
1016 * and all of the algorithms in the Collections class can be applied to
1017 * a subList.
1018 *
1019 * <p>The semantics of the List returned by this method become undefined if
1020 * the backing list (i.e., this List) is <i>structurally modified</i> in
1021 * any way other than via the returned List. (Structural modifications are
1022 * those that change the size of the List, or otherwise perturb it in such
1023 * a fashion that iterations in progress may yield incorrect results.)
1024 *
1025 * @param fromIndex low endpoint (inclusive) of the subList
1026 * @param toIndex high endpoint (exclusive) of the subList
1027 * @return a view of the specified range within this List
1028 * @throws IndexOutOfBoundsException if an endpoint index value is out of range
1029 * {@code (fromIndex < 0 || toIndex > size)}
1030 * @throws IllegalArgumentException if the endpoint indices are out of order
1031 * {@code (fromIndex > toIndex)}
1032 */
1033 public synchronized List<E> subList(int fromIndex, int toIndex) {
1034 return Collections.synchronizedList(super.subList(fromIndex, toIndex),
1035 this);
1036 }
1037
1038 /**
1039 * Removes from this list all of the elements whose index is between
1040 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
1041 * Shifts any succeeding elements to the left (reduces their index).
1042 * This call shortens the list by {@code (toIndex - fromIndex)} elements.
1043 * (If {@code toIndex==fromIndex}, this operation has no effect.)
1044 */
1045 protected synchronized void removeRange(int fromIndex, int toIndex) {
1046 modCount++;
1047 int numMoved = elementCount - toIndex;
1048 System.arraycopy(elementData, toIndex, elementData, fromIndex,
1049 numMoved);
1050
1051 // Let gc do its work
1052 int newElementCount = elementCount - (toIndex-fromIndex);
1053 while (elementCount != newElementCount)
1054 elementData[--elementCount] = null;
1055 }
1056
1057 /**
1058 * Save the state of the {@code Vector} instance to a stream (that
1059 * is, serialize it).
1060 * This method performs synchronization to ensure the consistency
1061 * of the serialized data.
1062 */
1063 private void writeObject(java.io.ObjectOutputStream s)
1064 throws java.io.IOException {
1065 final java.io.ObjectOutputStream.PutField fields = s.putFields();
1066 final Object[] data;
1067 synchronized (this) {
1068 fields.put("capacityIncrement", capacityIncrement);
1069 fields.put("elementCount", elementCount);
1070 data = elementData.clone();
1071 }
1072 fields.put("elementData", data);
1073 s.writeFields();
1074 }
1075
1076 /**
1077 * Returns a list iterator over the elements in this list (in proper
1078 * sequence), starting at the specified position in the list.
1079 * The specified index indicates the first element that would be
1080 * returned by an initial call to {@link ListIterator#next next}.
1081 * An initial call to {@link ListIterator#previous previous} would
1082 * return the element with the specified index minus one.
1083 *
1084 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
1085 *
1086 * @throws IndexOutOfBoundsException {@inheritDoc}
1087 */
1088 public synchronized ListIterator<E> listIterator(int index) {
1089 if (index < 0 || index > elementCount)
1090 throw new IndexOutOfBoundsException("Index: "+index);
1091 return new ListItr(index);
1092 }
1093
1094 /**
1095 * Returns a list iterator over the elements in this list (in proper
1096 * sequence).
1097 *
1098 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
1099 *
1100 * @see #listIterator(int)
1101 */
1102 public synchronized ListIterator<E> listIterator() {
1103 return new ListItr(0);
1104 }
1105
1106 /**
1107 * Returns an iterator over the elements in this list in proper sequence.
1108 *
1109 * <p>The returned iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
1110 *
1111 * @return an iterator over the elements in this list in proper sequence
1112 */
1113 public synchronized Iterator<E> iterator() {
1114 return new Itr();
1115 }
1116
1117 /**
1118 * An optimized version of AbstractList.Itr
1119 */
1120 private class Itr implements Iterator<E> {
1121 int cursor; // index of next element to return
1122 int lastRet = -1; // index of last element returned; -1 if no such
1123 int expectedModCount = modCount;
1124
1125 public boolean hasNext() {
1126 // Racy but within spec, since modifications are checked
1127 // within or after synchronization in next/previous
1128 return cursor != elementCount;
1129 }
1130
1131 public E next() {
1132 synchronized (Vector.this) {
1133 checkForComodification();
1134 int i = cursor;
1135 if (i >= elementCount)
1136 throw new NoSuchElementException();
1137 cursor = i + 1;
1138 return elementData(lastRet = i);
1139 }
1140 }
1141
1142 public void remove() {
1143 if (lastRet == -1)
1144 throw new IllegalStateException();
1145 synchronized (Vector.this) {
1146 checkForComodification();
1147 Vector.this.remove(lastRet);
1148 expectedModCount = modCount;
1149 }
1150 cursor = lastRet;
1151 lastRet = -1;
1152 }
1153
1154 final void checkForComodification() {
1155 if (modCount != expectedModCount)
1156 throw new ConcurrentModificationException();
1157 }
1158 }
1159
1160 /**
1161 * An optimized version of AbstractList.ListItr
1162 */
1163 final class ListItr extends Itr implements ListIterator<E> {
1164 ListItr(int index) {
1165 super();
1166 cursor = index;
1167 }
1168
1169 public boolean hasPrevious() {
1170 return cursor != 0;
1171 }
1172
1173 public int nextIndex() {
1174 return cursor;
1175 }
1176
1177 public int previousIndex() {
1178 return cursor - 1;
1179 }
1180
1181 public E previous() {
1182 synchronized (Vector.this) {
1183 checkForComodification();
1184 int i = cursor - 1;
1185 if (i < 0)
1186 throw new NoSuchElementException();
1187 cursor = i;
1188 return elementData(lastRet = i);
1189 }
1190 }
1191
1192 public void set(E e) {
1193 if (lastRet == -1)
1194 throw new IllegalStateException();
1195 synchronized (Vector.this) {
1196 checkForComodification();
1197 Vector.this.set(lastRet, e);
1198 }
1199 }
1200
1201 public void add(E e) {
1202 int i = cursor;
1203 synchronized (Vector.this) {
1204 checkForComodification();
1205 Vector.this.add(i, e);
1206 expectedModCount = modCount;
1207 }
1208 cursor = i + 1;
1209 lastRet = -1;
1210 }
1211 }
1212 }
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