1 /*
2 * Copyright (c) 1994, 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 * 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 @Override
668 public synchronized Vector<E> clone() {
669 try {
670 @SuppressWarnings("unchecked")
671 Vector<E> v = (Vector<E>) super.clone();
672 v.elementData = Arrays.copyOf(elementData, elementCount);
673 v.modCount = 0;
674 return v;
675 } catch (CloneNotSupportedException e) {
676 // this shouldn't happen, since we are Cloneable
677 throw new InternalError(e);
678 }
679 }
680
681 /**
682 * Returns an array containing all of the elements in this Vector
683 * in the correct order.
684 *
685 * @since 1.2
686 */
687 public synchronized Object[] toArray() {
688 return Arrays.copyOf(elementData, elementCount);
689 }
690
691 /**
692 * Returns an array containing all of the elements in this Vector in the
693 * correct order; the runtime type of the returned array is that of the
694 * specified array. If the Vector fits in the specified array, it is
695 * returned therein. Otherwise, a new array is allocated with the runtime
696 * type of the specified array and the size of this Vector.
697 *
698 * <p>If the Vector fits in the specified array with room to spare
699 * (i.e., the array has more elements than the Vector),
700 * the element in the array immediately following the end of the
701 * Vector is set to null. (This is useful in determining the length
702 * of the Vector <em>only</em> if the caller knows that the Vector
703 * does not contain any null elements.)
704 *
705 * @param a the array into which the elements of the Vector are to
706 * be stored, if it is big enough; otherwise, a new array of the
707 * same runtime type is allocated for this purpose.
708 * @return an array containing the elements of the Vector
709 * @throws ArrayStoreException if the runtime type of a is not a supertype
710 * of the runtime type of every element in this Vector
711 * @throws NullPointerException if the given array is null
712 * @since 1.2
713 */
714 @SuppressWarnings("unchecked")
715 public synchronized <T> T[] toArray(T[] a) {
716 if (a.length < elementCount)
717 return (T[]) Arrays.copyOf(elementData, elementCount, a.getClass());
718
719 System.arraycopy(elementData, 0, a, 0, elementCount);
720
721 if (a.length > elementCount)
722 a[elementCount] = null;
723
724 return a;
725 }
726
727 // Positional Access Operations
728
729 @SuppressWarnings("unchecked")
730 E elementData(int index) {
731 return (E) elementData[index];
732 }
733
734 /**
735 * Returns the element at the specified position in this Vector.
736 *
737 * @param index index of the element to return
738 * @return object at the specified index
739 * @throws ArrayIndexOutOfBoundsException if the index is out of range
740 * ({@code index < 0 || index >= size()})
741 * @since 1.2
742 */
743 public synchronized E get(int index) {
744 if (index >= elementCount)
745 throw new ArrayIndexOutOfBoundsException(index);
746
747 return elementData(index);
748 }
749
750 /**
751 * Replaces the element at the specified position in this Vector with the
752 * specified element.
753 *
754 * @param index index of the element to replace
755 * @param element element to be stored at the specified position
756 * @return the element previously at the specified position
757 * @throws ArrayIndexOutOfBoundsException if the index is out of range
758 * ({@code index < 0 || index >= size()})
759 * @since 1.2
760 */
761 public synchronized E set(int index, E element) {
762 if (index >= elementCount)
763 throw new ArrayIndexOutOfBoundsException(index);
764
765 E oldValue = elementData(index);
766 elementData[index] = element;
767 return oldValue;
768 }
769
770 /**
771 * Appends the specified element to the end of this Vector.
772 *
773 * @param e element to be appended to this Vector
774 * @return {@code true} (as specified by {@link Collection#add})
775 * @since 1.2
776 */
777 public synchronized boolean add(E e) {
778 modCount++;
779 ensureCapacityHelper(elementCount + 1);
780 elementData[elementCount++] = e;
781 return true;
782 }
783
784 /**
785 * Removes the first occurrence of the specified element in this Vector
786 * If the Vector does not contain the element, it is unchanged. More
787 * formally, removes the element with the lowest index i such that
788 * {@code (o==null ? get(i)==null : o.equals(get(i)))} (if such
789 * an element exists).
790 *
791 * @param o element to be removed from this Vector, if present
792 * @return true if the Vector contained the specified element
793 * @since 1.2
794 */
795 public boolean remove(Object o) {
796 return removeElement(o);
797 }
798
799 /**
800 * Inserts the specified element at the specified position in this Vector.
801 * Shifts the element currently at that position (if any) and any
802 * subsequent elements to the right (adds one to their indices).
803 *
804 * @param index index at which the specified element is to be inserted
805 * @param element element to be inserted
806 * @throws ArrayIndexOutOfBoundsException if the index is out of range
807 * ({@code index < 0 || index > size()})
808 * @since 1.2
809 */
810 public void add(int index, E element) {
811 insertElementAt(element, index);
812 }
813
814 /**
815 * Removes the element at the specified position in this Vector.
816 * Shifts any subsequent elements to the left (subtracts one from their
817 * indices). Returns the element that was removed from the Vector.
818 *
819 * @throws ArrayIndexOutOfBoundsException if the index is out of range
820 * ({@code index < 0 || index >= size()})
821 * @param index the index of the element to be removed
822 * @return element that was removed
823 * @since 1.2
824 */
825 public synchronized E remove(int index) {
826 modCount++;
827 if (index >= elementCount)
828 throw new ArrayIndexOutOfBoundsException(index);
829 E oldValue = elementData(index);
830
831 int numMoved = elementCount - index - 1;
832 if (numMoved > 0)
833 System.arraycopy(elementData, index+1, elementData, index,
834 numMoved);
835 elementData[--elementCount] = null; // Let gc do its work
836
837 return oldValue;
838 }
839
840 /**
841 * Removes all of the elements from this Vector. The Vector will
842 * be empty after this call returns (unless it throws an exception).
843 *
844 * @since 1.2
845 */
846 public void clear() {
847 removeAllElements();
848 }
849
850 // Bulk Operations
851
852 /**
853 * Returns true if this Vector contains all of the elements in the
854 * specified Collection.
855 *
856 * @param c a collection whose elements will be tested for containment
857 * in this Vector
858 * @return true if this Vector contains all of the elements in the
859 * specified collection
860 * @throws NullPointerException if the specified collection is null
861 */
862 public synchronized boolean containsAll(Collection<?> c) {
863 return super.containsAll(c);
864 }
865
866 /**
867 * Appends all of the elements in the specified Collection to the end of
868 * this Vector, in the order that they are returned by the specified
869 * Collection's Iterator. The behavior of this operation is undefined if
870 * the specified Collection is modified while the operation is in progress.
871 * (This implies that the behavior of this call is undefined if the
872 * specified Collection is this Vector, and this Vector is nonempty.)
873 *
874 * @param c elements to be inserted into this Vector
875 * @return {@code true} if this Vector changed as a result of the call
876 * @throws NullPointerException if the specified collection is null
877 * @since 1.2
878 */
879 public synchronized boolean addAll(Collection<? extends E> c) {
880 modCount++;
881 Object[] a = c.toArray();
882 int numNew = a.length;
883 ensureCapacityHelper(elementCount + numNew);
884 System.arraycopy(a, 0, elementData, elementCount, numNew);
885 elementCount += numNew;
886 return numNew != 0;
887 }
888
889 /**
890 * Removes from this Vector all of its elements that are contained in the
891 * specified Collection.
892 *
893 * @param c a collection of elements to be removed from the Vector
894 * @return true if this Vector changed as a result of the call
895 * @throws ClassCastException if the types of one or more elements
896 * in this vector are incompatible with the specified
897 * collection
898 * (<a href="Collection.html#optional-restrictions">optional</a>)
899 * @throws NullPointerException if this vector contains one or more null
900 * elements and the specified collection does not support null
901 * elements
902 * (<a href="Collection.html#optional-restrictions">optional</a>),
903 * or if the specified collection is null
904 * @since 1.2
905 */
906 public synchronized boolean removeAll(Collection<?> c) {
907 return super.removeAll(c);
908 }
909
910 /**
911 * Retains only the elements in this Vector that are contained in the
912 * specified Collection. In other words, removes from this Vector all
913 * of its elements that are not contained in the specified Collection.
914 *
915 * @param c a collection of elements to be retained in this Vector
916 * (all other elements are removed)
917 * @return true if this Vector changed as a result of the call
918 * @throws ClassCastException if the types of one or more elements
919 * in this vector are incompatible with the specified
920 * collection
921 * (<a href="Collection.html#optional-restrictions">optional</a>)
922 * @throws NullPointerException if this vector contains one or more null
923 * elements and the specified collection does not support null
924 * elements
925 * (<a href="Collection.html#optional-restrictions">optional</a>),
926 * or if the specified collection is null
927 * @since 1.2
928 */
929 public synchronized boolean retainAll(Collection<?> c) {
930 return super.retainAll(c);
931 }
932
933 /**
934 * Inserts all of the elements in the specified Collection into this
935 * Vector at the specified position. Shifts the element currently at
936 * that position (if any) and any subsequent elements to the right
937 * (increases their indices). The new elements will appear in the Vector
938 * in the order that they are returned by the specified Collection's
939 * iterator.
940 *
941 * @param index index at which to insert the first element from the
942 * specified collection
943 * @param c elements to be inserted into this Vector
944 * @return {@code true} if this Vector changed as a result of the call
945 * @throws ArrayIndexOutOfBoundsException if the index is out of range
946 * ({@code index < 0 || index > size()})
947 * @throws NullPointerException if the specified collection is null
948 * @since 1.2
949 */
950 public synchronized boolean addAll(int index, Collection<? extends E> c) {
951 modCount++;
952 if (index < 0 || index > elementCount)
953 throw new ArrayIndexOutOfBoundsException(index);
954
955 Object[] a = c.toArray();
956 int numNew = a.length;
957 ensureCapacityHelper(elementCount + numNew);
958
959 int numMoved = elementCount - index;
960 if (numMoved > 0)
961 System.arraycopy(elementData, index, elementData, index + numNew,
962 numMoved);
963
964 System.arraycopy(a, 0, elementData, index, numNew);
965 elementCount += numNew;
966 return numNew != 0;
967 }
968
969 /**
970 * Compares the specified Object with this Vector for equality. Returns
971 * true if and only if the specified Object is also a List, both Lists
972 * have the same size, and all corresponding pairs of elements in the two
973 * Lists are <em>equal</em>. (Two elements {@code e1} and
974 * {@code e2} are <em>equal</em> if {@code (e1==null ? e2==null :
975 * e1.equals(e2))}.) In other words, two Lists are defined to be
976 * equal if they contain the same elements in the same order.
977 *
978 * @param o the Object to be compared for equality with this Vector
979 * @return true if the specified Object is equal to this Vector
980 */
981 public synchronized boolean equals(Object o) {
982 return super.equals(o);
983 }
984
985 /**
986 * Returns the hash code value for this Vector.
987 */
988 public synchronized int hashCode() {
989 return super.hashCode();
990 }
991
992 /**
993 * Returns a string representation of this Vector, containing
994 * the String representation of each element.
995 */
996 public synchronized String toString() {
997 return super.toString();
998 }
999
1000 /**
1001 * Returns a view of the portion of this List between fromIndex,
1002 * inclusive, and toIndex, exclusive. (If fromIndex and toIndex are
1003 * equal, the returned List is empty.) The returned List is backed by this
1004 * List, so changes in the returned List are reflected in this List, and
1005 * vice-versa. The returned List supports all of the optional List
1006 * operations supported by this List.
1007 *
1008 * <p>This method eliminates the need for explicit range operations (of
1009 * the sort that commonly exist for arrays). Any operation that expects
1010 * a List can be used as a range operation by operating on a subList view
1011 * instead of a whole List. For example, the following idiom
1012 * removes a range of elements from a List:
1013 * <pre>
1014 * list.subList(from, to).clear();
1015 * </pre>
1016 * Similar idioms may be constructed for indexOf and lastIndexOf,
1017 * and all of the algorithms in the Collections class can be applied to
1018 * a subList.
1019 *
1020 * <p>The semantics of the List returned by this method become undefined if
1021 * the backing list (i.e., this List) is <i>structurally modified</i> in
1022 * any way other than via the returned List. (Structural modifications are
1023 * those that change the size of the List, or otherwise perturb it in such
1024 * a fashion that iterations in progress may yield incorrect results.)
1025 *
1026 * @param fromIndex low endpoint (inclusive) of the subList
1027 * @param toIndex high endpoint (exclusive) of the subList
1028 * @return a view of the specified range within this List
1029 * @throws IndexOutOfBoundsException if an endpoint index value is out of range
1030 * {@code (fromIndex < 0 || toIndex > size)}
1031 * @throws IllegalArgumentException if the endpoint indices are out of order
1032 * {@code (fromIndex > toIndex)}
1033 */
1034 public synchronized List<E> subList(int fromIndex, int toIndex) {
1035 return Collections.synchronizedList(super.subList(fromIndex, toIndex),
1036 this);
1037 }
1038
1039 /**
1040 * Removes from this list all of the elements whose index is between
1041 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
1042 * Shifts any succeeding elements to the left (reduces their index).
1043 * This call shortens the list by {@code (toIndex - fromIndex)} elements.
1044 * (If {@code toIndex==fromIndex}, this operation has no effect.)
1045 */
1046 protected synchronized void removeRange(int fromIndex, int toIndex) {
1047 modCount++;
1048 int numMoved = elementCount - toIndex;
1049 System.arraycopy(elementData, toIndex, elementData, fromIndex,
1050 numMoved);
1051
1052 // Let gc do its work
1053 int newElementCount = elementCount - (toIndex-fromIndex);
1054 while (elementCount != newElementCount)
1055 elementData[--elementCount] = null;
1056 }
1057
1058 /**
1059 * Save the state of the {@code Vector} instance to a stream (that
1060 * is, serialize it).
1061 * This method performs synchronization to ensure the consistency
1062 * of the serialized data.
1063 */
1064 private void writeObject(java.io.ObjectOutputStream s)
1065 throws java.io.IOException {
1066 final java.io.ObjectOutputStream.PutField fields = s.putFields();
1067 final Object[] data;
1068 synchronized (this) {
1069 fields.put("capacityIncrement", capacityIncrement);
1070 fields.put("elementCount", elementCount);
1071 data = elementData.clone();
1072 }
1073 fields.put("elementData", data);
1074 s.writeFields();
1075 }
1076
1077 /**
1078 * Returns a list iterator over the elements in this list (in proper
1079 * sequence), starting at the specified position in the list.
1080 * The specified index indicates the first element that would be
1081 * returned by an initial call to {@link ListIterator#next next}.
1082 * An initial call to {@link ListIterator#previous previous} would
1083 * return the element with the specified index minus one.
1084 *
1085 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
1086 *
1087 * @throws IndexOutOfBoundsException {@inheritDoc}
1088 */
1089 public synchronized ListIterator<E> listIterator(int index) {
1090 if (index < 0 || index > elementCount)
1091 throw new IndexOutOfBoundsException("Index: "+index);
1092 return new ListItr(index);
1093 }
1094
1095 /**
1096 * Returns a list iterator over the elements in this list (in proper
1097 * sequence).
1098 *
1099 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
1100 *
1101 * @see #listIterator(int)
1102 */
1103 public synchronized ListIterator<E> listIterator() {
1104 return new ListItr(0);
1105 }
1106
1107 /**
1108 * Returns an iterator over the elements in this list in proper sequence.
1109 *
1110 * <p>The returned iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
1111 *
1112 * @return an iterator over the elements in this list in proper sequence
1113 */
1114 public synchronized Iterator<E> iterator() {
1115 return new Itr();
1116 }
1117
1118 /**
1119 * An optimized version of AbstractList.Itr
1120 */
1121 private class Itr implements Iterator<E> {
1122 int cursor; // index of next element to return
1123 int lastRet = -1; // index of last element returned; -1 if no such
1124 int expectedModCount = modCount;
1125
1126 public boolean hasNext() {
1127 // Racy but within spec, since modifications are checked
1128 // within or after synchronization in next/previous
1129 return cursor != elementCount;
1130 }
1131
1132 public E next() {
1133 synchronized (Vector.this) {
1134 checkForComodification();
1135 int i = cursor;
1136 if (i >= elementCount)
1137 throw new NoSuchElementException();
1138 cursor = i + 1;
1139 return elementData(lastRet = i);
1140 }
1141 }
1142
1143 public void remove() {
1144 if (lastRet == -1)
1145 throw new IllegalStateException();
1146 synchronized (Vector.this) {
1147 checkForComodification();
1148 Vector.this.remove(lastRet);
1149 expectedModCount = modCount;
1150 }
1151 cursor = lastRet;
1152 lastRet = -1;
1153 }
1154
1155 final void checkForComodification() {
1156 if (modCount != expectedModCount)
1157 throw new ConcurrentModificationException();
1158 }
1159 }
1160
1161 /**
1162 * An optimized version of AbstractList.ListItr
1163 */
1164 final class ListItr extends Itr implements ListIterator<E> {
1165 ListItr(int index) {
1166 super();
1167 cursor = index;
1168 }
1169
1170 public boolean hasPrevious() {
1171 return cursor != 0;
1172 }
1173
1174 public int nextIndex() {
1175 return cursor;
1176 }
1177
1178 public int previousIndex() {
1179 return cursor - 1;
1180 }
1181
1182 public E previous() {
1183 synchronized (Vector.this) {
1184 checkForComodification();
1185 int i = cursor - 1;
1186 if (i < 0)
1187 throw new NoSuchElementException();
1188 cursor = i;
1189 return elementData(lastRet = i);
1190 }
1191 }
1192
1193 public void set(E e) {
1194 if (lastRet == -1)
1195 throw new IllegalStateException();
1196 synchronized (Vector.this) {
1197 checkForComodification();
1198 Vector.this.set(lastRet, e);
1199 }
1200 }
1201
1202 public void add(E e) {
1203 int i = cursor;
1204 synchronized (Vector.this) {
1205 checkForComodification();
1206 Vector.this.add(i, e);
1207 expectedModCount = modCount;
1208 }
1209 cursor = i + 1;
1210 lastRet = -1;
1211 }
1212 }
1213 }