1 /*
2 * Copyright (c) 1994, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.util;
27
28 import java.io.IOException;
29 import java.io.ObjectInputStream;
30 import java.io.StreamCorruptedException;
31 import java.util.function.Consumer;
32 import java.util.function.Predicate;
33 import java.util.function.UnaryOperator;
34
35 /**
36 * The {@code Vector} class implements a growable array of
37 * objects. Like an array, it contains components that can be
38 * accessed using an integer index. However, the size of a
39 * {@code Vector} can grow or shrink as needed to accommodate
40 * adding and removing items after the {@code Vector} has been created.
41 *
42 * <p>Each vector tries to optimize storage management by maintaining a
43 * {@code capacity} and a {@code capacityIncrement}. The
44 * {@code capacity} is always at least as large as the vector
45 * size; it is usually larger because as components are added to the
46 * vector, the vector's storage increases in chunks the size of
47 * {@code capacityIncrement}. An application can increase the
48 * capacity of a vector before inserting a large number of
49 * components; this reduces the amount of incremental reallocation.
50 *
51 * <p id="fail-fast">
52 * The iterators returned by this class's {@link #iterator() iterator} and
53 * {@link #listIterator(int) listIterator} methods are <em>fail-fast</em>:
54 * if the vector is structurally modified at any time after the iterator is
55 * created, in any way except through the iterator's own
56 * {@link ListIterator#remove() remove} or
57 * {@link ListIterator#add(Object) add} methods, the iterator will throw a
58 * {@link ConcurrentModificationException}. Thus, in the face of
59 * concurrent modification, the iterator fails quickly and cleanly, rather
60 * than risking arbitrary, non-deterministic behavior at an undetermined
61 * time in the future. The {@link Enumeration Enumerations} returned by
62 * the {@link #elements() elements} method are <em>not</em> fail-fast; if the
63 * Vector is structurally modified at any time after the enumeration is
64 * created then the results of enumerating are undefined.
65 *
66 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
67 * as it is, generally speaking, impossible to make any hard guarantees in the
68 * presence of unsynchronized concurrent modification. Fail-fast iterators
69 * throw {@code ConcurrentModificationException} on a best-effort basis.
70 * Therefore, it would be wrong to write a program that depended on this
71 * exception for its correctness: <i>the fail-fast behavior of iterators
72 * should be used only to detect bugs.</i>
73 *
74 * <p>As of the Java 2 platform v1.2, this class was retrofitted to
75 * implement the {@link List} interface, making it a member of the
76 * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
77 * Java Collections Framework</a>. Unlike the new collection
78 * implementations, {@code Vector} is synchronized. If a thread-safe
79 * implementation is not needed, it is recommended to use {@link
80 * ArrayList} in place of {@code Vector}.
81 *
82 * @param <E> Type of component elements
83 *
84 * @author Lee Boynton
85 * @author Jonathan Payne
86 * @see Collection
87 * @see LinkedList
88 * @since 1.0
89 */
90 public class Vector<E>
91 extends AbstractList<E>
92 implements List<E>, RandomAccess, Cloneable, java.io.Serializable
93 {
94 /**
95 * The array buffer into which the components of the vector are
96 * stored. The capacity of the vector is the length of this array buffer,
97 * and is at least large enough to contain all the vector's elements.
98 *
99 * <p>Any array elements following the last element in the Vector are null.
100 *
101 * @serial
102 */
103 protected Object[] elementData;
104
105 /**
106 * The number of valid components in this {@code Vector} object.
107 * Components {@code elementData[0]} through
108 * {@code elementData[elementCount-1]} are the actual items.
109 *
110 * @serial
111 */
112 protected int elementCount;
113
114 /**
115 * The amount by which the capacity of the vector is automatically
116 * incremented when its size becomes greater than its capacity. If
117 * the capacity increment is less than or equal to zero, the capacity
118 * of the vector is doubled each time it needs to grow.
119 *
120 * @serial
121 */
122 protected int capacityIncrement;
123
124 /** use serialVersionUID from JDK 1.0.2 for interoperability */
125 private static final long serialVersionUID = -2767605614048989439L;
126
127 /**
128 * Constructs an empty vector with the specified initial capacity and
129 * capacity increment.
130 *
131 * @param initialCapacity the initial capacity of the vector
132 * @param capacityIncrement the amount by which the capacity is
133 * increased when the vector overflows
134 * @throws IllegalArgumentException if the specified initial capacity
135 * is negative
136 */
137 public Vector(int initialCapacity, int capacityIncrement) {
138 super();
139 if (initialCapacity < 0)
140 throw new IllegalArgumentException("Illegal Capacity: "+
141 initialCapacity);
142 this.elementData = new Object[initialCapacity];
143 this.capacityIncrement = capacityIncrement;
144 }
145
146 /**
147 * Constructs an empty vector with the specified initial capacity and
148 * with its capacity increment equal to zero.
149 *
150 * @param initialCapacity the initial capacity of the vector
151 * @throws IllegalArgumentException if the specified initial capacity
152 * is negative
153 */
154 public Vector(int initialCapacity) {
155 this(initialCapacity, 0);
156 }
157
158 /**
159 * Constructs an empty vector so that its internal data array
160 * has size {@code 10} and its standard capacity increment is
161 * zero.
162 */
163 public Vector() {
164 this(10);
165 }
166
167 /**
168 * Constructs a vector containing the elements of the specified
169 * collection, in the order they are returned by the collection's
170 * iterator.
171 *
172 * @param c the collection whose elements are to be placed into this
173 * vector
174 * @throws NullPointerException if the specified collection is null
175 * @since 1.2
176 */
177 public Vector(Collection<? extends E> c) {
178 elementData = c.toArray();
179 elementCount = elementData.length;
180 // defend against c.toArray (incorrectly) not returning Object[]
181 // (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652)
182 if (elementData.getClass() != Object[].class)
183 elementData = Arrays.copyOf(elementData, elementCount, Object[].class);
184 }
185
186 /**
187 * Copies the components of this vector into the specified array.
188 * The item at index {@code k} in this vector is copied into
189 * component {@code k} of {@code anArray}.
190 *
191 * @param anArray the array into which the components get copied
192 * @throws NullPointerException if the given array is null
193 * @throws IndexOutOfBoundsException if the specified array is not
194 * large enough to hold all the components of this vector
195 * @throws ArrayStoreException if a component of this vector is not of
196 * a runtime type that can be stored in the specified array
197 * @see #toArray(Object[])
198 */
199 public synchronized void copyInto(Object[] anArray) {
200 System.arraycopy(elementData, 0, anArray, 0, elementCount);
201 }
202
203 /**
204 * Trims the capacity of this vector to be the vector's current
205 * size. If the capacity of this vector is larger than its current
206 * size, then the capacity is changed to equal the size by replacing
207 * its internal data array, kept in the field {@code elementData},
208 * with a smaller one. An application can use this operation to
209 * minimize the storage of a vector.
210 */
211 public synchronized void trimToSize() {
212 modCount++;
213 int oldCapacity = elementData.length;
214 if (elementCount < oldCapacity) {
215 elementData = Arrays.copyOf(elementData, elementCount);
216 }
217 }
218
219 /**
220 * Increases the capacity of this vector, if necessary, to ensure
221 * that it can hold at least the number of components specified by
222 * the minimum capacity argument.
223 *
224 * <p>If the current capacity of this vector is less than
225 * {@code minCapacity}, then its capacity is increased by replacing its
226 * internal data array, kept in the field {@code elementData}, with a
227 * larger one. The size of the new data array will be the old size plus
228 * {@code capacityIncrement}, unless the value of
229 * {@code capacityIncrement} is less than or equal to zero, in which case
230 * the new capacity will be twice the old capacity; but if this new size
231 * is still smaller than {@code minCapacity}, then the new capacity will
232 * be {@code minCapacity}.
233 *
234 * @param minCapacity the desired minimum capacity
235 */
236 public synchronized void ensureCapacity(int minCapacity) {
237 if (minCapacity > 0) {
238 modCount++;
239 if (minCapacity > elementData.length)
240 grow(minCapacity);
241 }
242 }
243
244 /**
245 * The maximum size of array to allocate (unless necessary).
246 * Some VMs reserve some header words in an array.
247 * Attempts to allocate larger arrays may result in
248 * OutOfMemoryError: Requested array size exceeds VM limit
249 */
250 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
251
252 /**
253 * Increases the capacity to ensure that it can hold at least the
254 * number of elements specified by the minimum capacity argument.
255 *
256 * @param minCapacity the desired minimum capacity
257 * @throws OutOfMemoryError if minCapacity is less than zero
258 */
259 private Object[] grow(int minCapacity) {
260 return elementData = Arrays.copyOf(elementData,
261 newCapacity(minCapacity));
262 }
263
264 private Object[] grow() {
265 return grow(elementCount + 1);
266 }
267
268 /**
269 * Returns a capacity at least as large as the given minimum capacity.
270 * Will not return a capacity greater than MAX_ARRAY_SIZE unless
271 * the given minimum capacity is greater than MAX_ARRAY_SIZE.
272 *
273 * @param minCapacity the desired minimum capacity
274 * @throws OutOfMemoryError if minCapacity is less than zero
275 */
276 private int newCapacity(int minCapacity) {
277 // overflow-conscious code
278 int oldCapacity = elementData.length;
279 int newCapacity = oldCapacity + ((capacityIncrement > 0) ?
280 capacityIncrement : oldCapacity);
281 if (newCapacity - minCapacity <= 0) {
282 if (minCapacity < 0) // overflow
283 throw new OutOfMemoryError();
284 return minCapacity;
285 }
286 return (newCapacity - MAX_ARRAY_SIZE <= 0)
287 ? newCapacity
288 : hugeCapacity(minCapacity);
289 }
290
291 private static int hugeCapacity(int minCapacity) {
292 if (minCapacity < 0) // overflow
293 throw new OutOfMemoryError();
294 return (minCapacity > MAX_ARRAY_SIZE) ?
295 Integer.MAX_VALUE :
296 MAX_ARRAY_SIZE;
297 }
298
299 /**
300 * Sets the size of this vector. If the new size is greater than the
301 * current size, new {@code null} items are added to the end of
302 * the vector. If the new size is less than the current size, all
303 * components at index {@code newSize} and greater are discarded.
304 *
305 * @param newSize the new size of this vector
306 * @throws ArrayIndexOutOfBoundsException if the new size is negative
307 */
308 public synchronized void setSize(int newSize) {
309 modCount++;
310 if (newSize > elementData.length)
311 grow(newSize);
312 final Object[] es = elementData;
313 for (int to = elementCount, i = newSize; i < to; i++)
314 es[i] = null;
315 elementCount = newSize;
316 }
317
318 /**
319 * Returns the current capacity of this vector.
320 *
321 * @return the current capacity (the length of its internal
322 * data array, kept in the field {@code elementData}
323 * of this vector)
324 */
325 public synchronized int capacity() {
326 return elementData.length;
327 }
328
329 /**
330 * Returns the number of components in this vector.
331 *
332 * @return the number of components in this vector
333 */
334 public synchronized int size() {
335 return elementCount;
336 }
337
338 /**
339 * Tests if this vector has no components.
340 *
341 * @return {@code true} if and only if this vector has
342 * no components, that is, its size is zero;
343 * {@code false} otherwise.
344 */
345 public synchronized boolean isEmpty() {
346 return elementCount == 0;
347 }
348
349 /**
350 * Returns an enumeration of the components of this vector. The
351 * returned {@code Enumeration} object will generate all items in
352 * this vector. The first item generated is the item at index {@code 0},
353 * then the item at index {@code 1}, and so on. If the vector is
354 * structurally modified while enumerating over the elements then the
355 * results of enumerating are undefined.
356 *
357 * @return an enumeration of the components of this vector
358 * @see Iterator
359 */
360 public Enumeration<E> elements() {
361 return new Enumeration<E>() {
362 int count = 0;
363
364 public boolean hasMoreElements() {
365 return count < elementCount;
366 }
367
368 public E nextElement() {
369 synchronized (Vector.this) {
370 if (count < elementCount) {
371 return elementData(count++);
372 }
373 }
374 throw new NoSuchElementException("Vector Enumeration");
375 }
376 };
377 }
378
379 /**
380 * Returns {@code true} if this vector contains the specified element.
381 * More formally, returns {@code true} if and only if this vector
382 * contains at least one element {@code e} such that
383 * {@code Objects.equals(o, e)}.
384 *
385 * @param o element whose presence in this vector is to be tested
386 * @return {@code true} if this vector contains the specified element
387 */
388 public boolean contains(Object o) {
389 return indexOf(o, 0) >= 0;
390 }
391
392 /**
393 * Returns the index of the first occurrence of the specified element
394 * in this vector, or -1 if this vector does not contain the element.
395 * More formally, returns the lowest index {@code i} such that
396 * {@code Objects.equals(o, get(i))},
397 * or -1 if there is no such index.
398 *
399 * @param o element to search for
400 * @return the index of the first occurrence of the specified element in
401 * this vector, or -1 if this vector does not contain the element
402 */
403 public int indexOf(Object o) {
404 return indexOf(o, 0);
405 }
406
407 /**
408 * Returns the index of the first occurrence of the specified element in
409 * this vector, searching forwards from {@code index}, or returns -1 if
410 * the element is not found.
411 * More formally, returns the lowest index {@code i} such that
412 * {@code (i >= index && Objects.equals(o, get(i)))},
413 * or -1 if there is no such index.
414 *
415 * @param o element to search for
416 * @param index index to start searching from
417 * @return the index of the first occurrence of the element in
418 * this vector at position {@code index} or later in the vector;
419 * {@code -1} if the element is not found.
420 * @throws IndexOutOfBoundsException if the specified index is negative
421 * @see Object#equals(Object)
422 */
423 public synchronized int indexOf(Object o, int index) {
424 if (o == null) {
425 for (int i = index ; i < elementCount ; i++)
426 if (elementData[i]==null)
427 return i;
428 } else {
429 for (int i = index ; i < elementCount ; i++)
430 if (o.equals(elementData[i]))
431 return i;
432 }
433 return -1;
434 }
435
436 /**
437 * Returns the index of the last occurrence of the specified element
438 * in this vector, or -1 if this vector does not contain the element.
439 * More formally, returns the highest index {@code i} such that
440 * {@code Objects.equals(o, get(i))},
441 * or -1 if there is no such index.
442 *
443 * @param o element to search for
444 * @return the index of the last occurrence of the specified element in
445 * this vector, or -1 if this vector does not contain the element
446 */
447 public synchronized int lastIndexOf(Object o) {
448 return lastIndexOf(o, elementCount-1);
449 }
450
451 /**
452 * Returns the index of the last occurrence of the specified element in
453 * this vector, searching backwards from {@code index}, or returns -1 if
454 * the element is not found.
455 * More formally, returns the highest index {@code i} such that
456 * {@code (i <= index && Objects.equals(o, get(i)))},
457 * or -1 if there is no such index.
458 *
459 * @param o element to search for
460 * @param index index to start searching backwards from
461 * @return the index of the last occurrence of the element at position
462 * less than or equal to {@code index} in this vector;
463 * -1 if the element is not found.
464 * @throws IndexOutOfBoundsException if the specified index is greater
465 * than or equal to the current size of this vector
466 */
467 public synchronized int lastIndexOf(Object o, int index) {
468 if (index >= elementCount)
469 throw new IndexOutOfBoundsException(index + " >= "+ elementCount);
470
471 if (o == null) {
472 for (int i = index; i >= 0; i--)
473 if (elementData[i]==null)
474 return i;
475 } else {
476 for (int i = index; i >= 0; i--)
477 if (o.equals(elementData[i]))
478 return i;
479 }
480 return -1;
481 }
482
483 /**
484 * Returns the component at the specified index.
485 *
486 * <p>This method is identical in functionality to the {@link #get(int)}
487 * method (which is part of the {@link List} interface).
488 *
489 * @param index an index into this vector
490 * @return the component at the specified index
491 * @throws ArrayIndexOutOfBoundsException if the index is out of range
492 * ({@code index < 0 || index >= size()})
493 */
494 public synchronized E elementAt(int index) {
495 if (index >= elementCount) {
496 throw new ArrayIndexOutOfBoundsException(index + " >= " + elementCount);
497 }
498
499 return elementData(index);
500 }
501
502 /**
503 * Returns the first component (the item at index {@code 0}) of
504 * this vector.
505 *
506 * @return the first component of this vector
507 * @throws NoSuchElementException if this vector has no components
508 */
509 public synchronized E firstElement() {
510 if (elementCount == 0) {
511 throw new NoSuchElementException();
512 }
513 return elementData(0);
514 }
515
516 /**
517 * Returns the last component of the vector.
518 *
519 * @return the last component of the vector, i.e., the component at index
520 * {@code size() - 1}
521 * @throws NoSuchElementException if this vector is empty
522 */
523 public synchronized E lastElement() {
524 if (elementCount == 0) {
525 throw new NoSuchElementException();
526 }
527 return elementData(elementCount - 1);
528 }
529
530 /**
531 * Sets the component at the specified {@code index} of this
532 * vector to be the specified object. The previous component at that
533 * position is discarded.
534 *
535 * <p>The index must be a value greater than or equal to {@code 0}
536 * and less than the current size of the vector.
537 *
538 * <p>This method is identical in functionality to the
539 * {@link #set(int, Object) set(int, E)}
540 * method (which is part of the {@link List} interface). Note that the
541 * {@code set} method reverses the order of the parameters, to more closely
542 * match array usage. Note also that the {@code set} method returns the
543 * old value that was stored at the specified position.
544 *
545 * @param obj what the component is to be set to
546 * @param index the specified index
547 * @throws ArrayIndexOutOfBoundsException if the index is out of range
548 * ({@code index < 0 || index >= size()})
549 */
550 public synchronized void setElementAt(E obj, int index) {
551 if (index >= elementCount) {
552 throw new ArrayIndexOutOfBoundsException(index + " >= " +
553 elementCount);
554 }
555 elementData[index] = obj;
556 }
557
558 /**
559 * Deletes the component at the specified index. Each component in
560 * this vector with an index greater or equal to the specified
561 * {@code index} is shifted downward to have an index one
562 * smaller than the value it had previously. The size of this vector
563 * is decreased by {@code 1}.
564 *
565 * <p>The index must be a value greater than or equal to {@code 0}
566 * and less than the current size of the vector.
567 *
568 * <p>This method is identical in functionality to the {@link #remove(int)}
569 * method (which is part of the {@link List} interface). Note that the
570 * {@code remove} method returns the old value that was stored at the
571 * specified position.
572 *
573 * @param index the index of the object to remove
574 * @throws ArrayIndexOutOfBoundsException if the index is out of range
575 * ({@code index < 0 || index >= size()})
576 */
577 public synchronized void removeElementAt(int index) {
578 if (index >= elementCount) {
579 throw new ArrayIndexOutOfBoundsException(index + " >= " +
580 elementCount);
581 }
582 else if (index < 0) {
583 throw new ArrayIndexOutOfBoundsException(index);
584 }
585 int j = elementCount - index - 1;
586 if (j > 0) {
587 System.arraycopy(elementData, index + 1, elementData, index, j);
588 }
589 modCount++;
590 elementCount--;
591 elementData[elementCount] = null; /* to let gc do its work */
592 }
593
594 /**
595 * Inserts the specified object as a component in this vector at the
596 * specified {@code index}. Each component in this vector with
597 * an index greater or equal to the specified {@code index} is
598 * shifted upward to have an index one greater than the value it had
599 * previously.
600 *
601 * <p>The index must be a value greater than or equal to {@code 0}
602 * and less than or equal to the current size of the vector. (If the
603 * index is equal to the current size of the vector, the new element
604 * is appended to the Vector.)
605 *
606 * <p>This method is identical in functionality to the
607 * {@link #add(int, Object) add(int, E)}
608 * method (which is part of the {@link List} interface). Note that the
609 * {@code add} method reverses the order of the parameters, to more closely
610 * match array usage.
611 *
612 * @param obj the component to insert
613 * @param index where to insert the new component
614 * @throws ArrayIndexOutOfBoundsException if the index is out of range
615 * ({@code index < 0 || index > size()})
616 */
617 public synchronized void insertElementAt(E obj, int index) {
618 if (index > elementCount) {
619 throw new ArrayIndexOutOfBoundsException(index
620 + " > " + elementCount);
621 }
622 modCount++;
623 final int s = elementCount;
624 Object[] elementData = this.elementData;
625 if (s == elementData.length)
626 elementData = grow();
627 System.arraycopy(elementData, index,
628 elementData, index + 1,
629 s - index);
630 elementData[index] = obj;
631 elementCount = s + 1;
632 }
633
634 /**
635 * Adds the specified component to the end of this vector,
636 * increasing its size by one. The capacity of this vector is
637 * increased if its size becomes greater than its capacity.
638 *
639 * <p>This method is identical in functionality to the
640 * {@link #add(Object) add(E)}
641 * method (which is part of the {@link List} interface).
642 *
643 * @param obj the component to be added
644 */
645 public synchronized void addElement(E obj) {
646 modCount++;
647 add(obj, elementData, elementCount);
648 }
649
650 /**
651 * Removes the first (lowest-indexed) occurrence of the argument
652 * from this vector. If the object is found in this vector, each
653 * component in the vector with an index greater or equal to the
654 * object's index is shifted downward to have an index one smaller
655 * than the value it had previously.
656 *
657 * <p>This method is identical in functionality to the
658 * {@link #remove(Object)} method (which is part of the
659 * {@link List} interface).
660 *
661 * @param obj the component to be removed
662 * @return {@code true} if the argument was a component of this
663 * vector; {@code false} otherwise.
664 */
665 public synchronized boolean removeElement(Object obj) {
666 modCount++;
667 int i = indexOf(obj);
668 if (i >= 0) {
669 removeElementAt(i);
670 return true;
671 }
672 return false;
673 }
674
675 /**
676 * Removes all components from this vector and sets its size to zero.
677 *
678 * <p>This method is identical in functionality to the {@link #clear}
679 * method (which is part of the {@link List} interface).
680 */
681 public synchronized void removeAllElements() {
682 final Object[] es = elementData;
683 for (int to = elementCount, i = elementCount = 0; i < to; i++)
684 es[i] = null;
685 modCount++;
686 }
687
688 /**
689 * Returns a clone of this vector. The copy will contain a
690 * reference to a clone of the internal data array, not a reference
691 * to the original internal data array of this {@code Vector} object.
692 *
693 * @return a clone of this vector
694 */
695 public synchronized Object clone() {
696 try {
697 @SuppressWarnings("unchecked")
698 Vector<E> v = (Vector<E>) super.clone();
699 v.elementData = Arrays.copyOf(elementData, elementCount);
700 v.modCount = 0;
701 return v;
702 } catch (CloneNotSupportedException e) {
703 // this shouldn't happen, since we are Cloneable
704 throw new InternalError(e);
705 }
706 }
707
708 /**
709 * Returns an array containing all of the elements in this Vector
710 * in the correct order.
711 *
712 * @since 1.2
713 */
714 public synchronized Object[] toArray() {
715 return Arrays.copyOf(elementData, elementCount);
716 }
717
718 /**
719 * Returns an array containing all of the elements in this Vector in the
720 * correct order; the runtime type of the returned array is that of the
721 * specified array. If the Vector fits in the specified array, it is
722 * returned therein. Otherwise, a new array is allocated with the runtime
723 * type of the specified array and the size of this Vector.
724 *
725 * <p>If the Vector fits in the specified array with room to spare
726 * (i.e., the array has more elements than the Vector),
727 * the element in the array immediately following the end of the
728 * Vector is set to null. (This is useful in determining the length
729 * of the Vector <em>only</em> if the caller knows that the Vector
730 * does not contain any null elements.)
731 *
732 * @param <T> type of array elements. The same type as {@code <E>} or a
733 * supertype of {@code <E>}.
734 * @param a the array into which the elements of the Vector are to
735 * be stored, if it is big enough; otherwise, a new array of the
736 * same runtime type is allocated for this purpose.
737 * @return an array containing the elements of the Vector
738 * @throws ArrayStoreException if the runtime type of a, {@code <T>}, is not
739 * a supertype of the runtime type, {@code <E>}, of every element in this
740 * Vector
741 * @throws NullPointerException if the given array is null
742 * @since 1.2
743 */
744 @SuppressWarnings("unchecked")
745 public synchronized <T> T[] toArray(T[] a) {
746 if (a.length < elementCount)
747 return (T[]) Arrays.copyOf(elementData, elementCount, a.getClass());
748
749 System.arraycopy(elementData, 0, a, 0, elementCount);
750
751 if (a.length > elementCount)
752 a[elementCount] = null;
753
754 return a;
755 }
756
757 // Positional Access Operations
758
759 @SuppressWarnings("unchecked")
760 E elementData(int index) {
761 return (E) elementData[index];
762 }
763
764 @SuppressWarnings("unchecked")
765 static <E> E elementAt(Object[] es, int index) {
766 return (E) es[index];
767 }
768
769 /**
770 * Returns the element at the specified position in this Vector.
771 *
772 * @param index index of the element to return
773 * @return object at the specified index
774 * @throws ArrayIndexOutOfBoundsException if the index is out of range
775 * ({@code index < 0 || index >= size()})
776 * @since 1.2
777 */
778 public synchronized E get(int index) {
779 if (index >= elementCount)
780 throw new ArrayIndexOutOfBoundsException(index);
781
782 return elementData(index);
783 }
784
785 /**
786 * Replaces the element at the specified position in this Vector with the
787 * specified element.
788 *
789 * @param index index of the element to replace
790 * @param element element to be stored at the specified position
791 * @return the element previously at the specified position
792 * @throws ArrayIndexOutOfBoundsException if the index is out of range
793 * ({@code index < 0 || index >= size()})
794 * @since 1.2
795 */
796 public synchronized E set(int index, E element) {
797 if (index >= elementCount)
798 throw new ArrayIndexOutOfBoundsException(index);
799
800 E oldValue = elementData(index);
801 elementData[index] = element;
802 return oldValue;
803 }
804
805 /**
806 * This helper method split out from add(E) to keep method
807 * bytecode size under 35 (the -XX:MaxInlineSize default value),
808 * which helps when add(E) is called in a C1-compiled loop.
809 */
810 private void add(E e, Object[] elementData, int s) {
811 if (s == elementData.length)
812 elementData = grow();
813 elementData[s] = e;
814 elementCount = s + 1;
815 }
816
817 /**
818 * Appends the specified element to the end of this Vector.
819 *
820 * @param e element to be appended to this Vector
821 * @return {@code true} (as specified by {@link Collection#add})
822 * @since 1.2
823 */
824 public synchronized boolean add(E e) {
825 modCount++;
826 add(e, elementData, elementCount);
827 return true;
828 }
829
830 /**
831 * Removes the first occurrence of the specified element in this Vector
832 * If the Vector does not contain the element, it is unchanged. More
833 * formally, removes the element with the lowest index i such that
834 * {@code Objects.equals(o, get(i))} (if such
835 * an element exists).
836 *
837 * @param o element to be removed from this Vector, if present
838 * @return true if the Vector contained the specified element
839 * @since 1.2
840 */
841 public boolean remove(Object o) {
842 return removeElement(o);
843 }
844
845 /**
846 * Inserts the specified element at the specified position in this Vector.
847 * Shifts the element currently at that position (if any) and any
848 * subsequent elements to the right (adds one to their indices).
849 *
850 * @param index index at which the specified element is to be inserted
851 * @param element element to be inserted
852 * @throws ArrayIndexOutOfBoundsException if the index is out of range
853 * ({@code index < 0 || index > size()})
854 * @since 1.2
855 */
856 public void add(int index, E element) {
857 insertElementAt(element, index);
858 }
859
860 /**
861 * Removes the element at the specified position in this Vector.
862 * Shifts any subsequent elements to the left (subtracts one from their
863 * indices). Returns the element that was removed from the Vector.
864 *
865 * @param index the index of the element to be removed
866 * @return element that was removed
867 * @throws ArrayIndexOutOfBoundsException if the index is out of range
868 * ({@code index < 0 || index >= size()})
869 * @since 1.2
870 */
871 public synchronized E remove(int index) {
872 modCount++;
873 if (index >= elementCount)
874 throw new ArrayIndexOutOfBoundsException(index);
875 E oldValue = elementData(index);
876
877 int numMoved = elementCount - index - 1;
878 if (numMoved > 0)
879 System.arraycopy(elementData, index+1, elementData, index,
880 numMoved);
881 elementData[--elementCount] = null; // Let gc do its work
882
883 return oldValue;
884 }
885
886 /**
887 * Removes all of the elements from this Vector. The Vector will
888 * be empty after this call returns (unless it throws an exception).
889 *
890 * @since 1.2
891 */
892 public void clear() {
893 removeAllElements();
894 }
895
896 // Bulk Operations
897
898 /**
899 * Returns true if this Vector contains all of the elements in the
900 * specified Collection.
901 *
902 * @param c a collection whose elements will be tested for containment
903 * in this Vector
904 * @return true if this Vector contains all of the elements in the
905 * specified collection
906 * @throws NullPointerException if the specified collection is null
907 */
908 public synchronized boolean containsAll(Collection<?> c) {
909 return super.containsAll(c);
910 }
911
912 /**
913 * Appends all of the elements in the specified Collection to the end of
914 * this Vector, in the order that they are returned by the specified
915 * Collection's Iterator. The behavior of this operation is undefined if
916 * the specified Collection is modified while the operation is in progress.
917 * (This implies that the behavior of this call is undefined if the
918 * specified Collection is this Vector, and this Vector is nonempty.)
919 *
920 * @param c elements to be inserted into this Vector
921 * @return {@code true} if this Vector changed as a result of the call
922 * @throws NullPointerException if the specified collection is null
923 * @since 1.2
924 */
925 public boolean addAll(Collection<? extends E> c) {
926 Object[] a = c.toArray();
927 modCount++;
928 int numNew = a.length;
929 if (numNew == 0)
930 return false;
931 synchronized (this) {
932 Object[] elementData = this.elementData;
933 final int s = elementCount;
934 if (numNew > elementData.length - s)
935 elementData = grow(s + numNew);
936 System.arraycopy(a, 0, elementData, s, numNew);
937 elementCount = s + numNew;
938 return true;
939 }
940 }
941
942 /**
943 * Removes from this Vector all of its elements that are contained in the
944 * specified Collection.
945 *
946 * @param c a collection of elements to be removed from the Vector
947 * @return true if this Vector changed as a result of the call
948 * @throws ClassCastException if the types of one or more elements
949 * in this vector are incompatible with the specified
950 * collection
951 * (<a href="Collection.html#optional-restrictions">optional</a>)
952 * @throws NullPointerException if this vector contains one or more null
953 * elements and the specified collection does not support null
954 * elements
955 * (<a href="Collection.html#optional-restrictions">optional</a>),
956 * or if the specified collection is null
957 * @since 1.2
958 */
959 public boolean removeAll(Collection<?> c) {
960 Objects.requireNonNull(c);
961 return bulkRemove(e -> c.contains(e));
962 }
963
964 /**
965 * Retains only the elements in this Vector that are contained in the
966 * specified Collection. In other words, removes from this Vector all
967 * of its elements that are not contained in the specified Collection.
968 *
969 * @param c a collection of elements to be retained in this Vector
970 * (all other elements are removed)
971 * @return true if this Vector changed as a result of the call
972 * @throws ClassCastException if the types of one or more elements
973 * in this vector are incompatible with the specified
974 * collection
975 * (<a href="Collection.html#optional-restrictions">optional</a>)
976 * @throws NullPointerException if this vector contains one or more null
977 * elements and the specified collection does not support null
978 * elements
979 * (<a href="Collection.html#optional-restrictions">optional</a>),
980 * or if the specified collection is null
981 * @since 1.2
982 */
983 public boolean retainAll(Collection<?> c) {
984 Objects.requireNonNull(c);
985 return bulkRemove(e -> !c.contains(e));
986 }
987
988 /**
989 * @throws NullPointerException {@inheritDoc}
990 */
991 @Override
992 public boolean removeIf(Predicate<? super E> filter) {
993 Objects.requireNonNull(filter);
994 return bulkRemove(filter);
995 }
996
997 // A tiny bit set implementation
998
999 private static long[] nBits(int n) {
1000 return new long[((n - 1) >> 6) + 1];
1001 }
1002 private static void setBit(long[] bits, int i) {
1003 bits[i >> 6] |= 1L << i;
1004 }
1005 private static boolean isClear(long[] bits, int i) {
1006 return (bits[i >> 6] & (1L << i)) == 0;
1007 }
1008
1009 private synchronized boolean bulkRemove(Predicate<? super E> filter) {
1010 int expectedModCount = modCount;
1011 final Object[] es = elementData;
1012 final int end = elementCount;
1013 int i;
1014 // Optimize for initial run of survivors
1015 for (i = 0; i < end && !filter.test(elementAt(es, i)); i++)
1016 ;
1017 // Tolerate predicates that reentrantly access the collection for
1018 // read (but writers still get CME), so traverse once to find
1019 // elements to delete, a second pass to physically expunge.
1020 if (i < end) {
1021 final int beg = i;
1022 final long[] deathRow = nBits(end - beg);
1023 deathRow[0] = 1L; // set bit 0
1024 for (i = beg + 1; i < end; i++)
1025 if (filter.test(elementAt(es, i)))
1026 setBit(deathRow, i - beg);
1027 if (modCount != expectedModCount)
1028 throw new ConcurrentModificationException();
1029 modCount++;
1030 int w = beg;
1031 for (i = beg; i < end; i++)
1032 if (isClear(deathRow, i - beg))
1033 es[w++] = es[i];
1034 for (i = elementCount = w; i < end; i++)
1035 es[i] = null;
1036 return true;
1037 } else {
1038 if (modCount != expectedModCount)
1039 throw new ConcurrentModificationException();
1040 return false;
1041 }
1042 }
1043
1044 /**
1045 * Inserts all of the elements in the specified Collection into this
1046 * Vector at the specified position. Shifts the element currently at
1047 * that position (if any) and any subsequent elements to the right
1048 * (increases their indices). The new elements will appear in the Vector
1049 * in the order that they are returned by the specified Collection's
1050 * iterator.
1051 *
1052 * @param index index at which to insert the first element from the
1053 * specified collection
1054 * @param c elements to be inserted into this Vector
1055 * @return {@code true} if this Vector changed as a result of the call
1056 * @throws ArrayIndexOutOfBoundsException if the index is out of range
1057 * ({@code index < 0 || index > size()})
1058 * @throws NullPointerException if the specified collection is null
1059 * @since 1.2
1060 */
1061 public synchronized boolean addAll(int index, Collection<? extends E> c) {
1062 if (index < 0 || index > elementCount)
1063 throw new ArrayIndexOutOfBoundsException(index);
1064
1065 Object[] a = c.toArray();
1066 modCount++;
1067 int numNew = a.length;
1068 if (numNew == 0)
1069 return false;
1070 Object[] elementData = this.elementData;
1071 final int s = elementCount;
1072 if (numNew > elementData.length - s)
1073 elementData = grow(s + numNew);
1074
1075 int numMoved = s - index;
1076 if (numMoved > 0)
1077 System.arraycopy(elementData, index,
1078 elementData, index + numNew,
1079 numMoved);
1080 System.arraycopy(a, 0, elementData, index, numNew);
1081 elementCount = s + numNew;
1082 return true;
1083 }
1084
1085 /**
1086 * Compares the specified Object with this Vector for equality. Returns
1087 * true if and only if the specified Object is also a List, both Lists
1088 * have the same size, and all corresponding pairs of elements in the two
1089 * Lists are <em>equal</em>. (Two elements {@code e1} and
1090 * {@code e2} are <em>equal</em> if {@code Objects.equals(e1, e2)}.)
1091 * In other words, two Lists are defined to be
1092 * equal if they contain the same elements in the same order.
1093 *
1094 * @param o the Object to be compared for equality with this Vector
1095 * @return true if the specified Object is equal to this Vector
1096 */
1097 public synchronized boolean equals(Object o) {
1098 return super.equals(o);
1099 }
1100
1101 /**
1102 * Returns the hash code value for this Vector.
1103 */
1104 public synchronized int hashCode() {
1105 return super.hashCode();
1106 }
1107
1108 /**
1109 * Returns a string representation of this Vector, containing
1110 * the String representation of each element.
1111 */
1112 public synchronized String toString() {
1113 return super.toString();
1114 }
1115
1116 /**
1117 * Returns a view of the portion of this List between fromIndex,
1118 * inclusive, and toIndex, exclusive. (If fromIndex and toIndex are
1119 * equal, the returned List is empty.) The returned List is backed by this
1120 * List, so changes in the returned List are reflected in this List, and
1121 * vice-versa. The returned List supports all of the optional List
1122 * operations supported by this List.
1123 *
1124 * <p>This method eliminates the need for explicit range operations (of
1125 * the sort that commonly exist for arrays). Any operation that expects
1126 * a List can be used as a range operation by operating on a subList view
1127 * instead of a whole List. For example, the following idiom
1128 * removes a range of elements from a List:
1129 * <pre>
1130 * list.subList(from, to).clear();
1131 * </pre>
1132 * Similar idioms may be constructed for indexOf and lastIndexOf,
1133 * and all of the algorithms in the Collections class can be applied to
1134 * a subList.
1135 *
1136 * <p>The semantics of the List returned by this method become undefined if
1137 * the backing list (i.e., this List) is <i>structurally modified</i> in
1138 * any way other than via the returned List. (Structural modifications are
1139 * those that change the size of the List, or otherwise perturb it in such
1140 * a fashion that iterations in progress may yield incorrect results.)
1141 *
1142 * @param fromIndex low endpoint (inclusive) of the subList
1143 * @param toIndex high endpoint (exclusive) of the subList
1144 * @return a view of the specified range within this List
1145 * @throws IndexOutOfBoundsException if an endpoint index value is out of range
1146 * {@code (fromIndex < 0 || toIndex > size)}
1147 * @throws IllegalArgumentException if the endpoint indices are out of order
1148 * {@code (fromIndex > toIndex)}
1149 */
1150 public synchronized List<E> subList(int fromIndex, int toIndex) {
1151 return Collections.synchronizedList(super.subList(fromIndex, toIndex),
1152 this);
1153 }
1154
1155 /**
1156 * Removes from this list all of the elements whose index is between
1157 * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
1158 * Shifts any succeeding elements to the left (reduces their index).
1159 * This call shortens the list by {@code (toIndex - fromIndex)} elements.
1160 * (If {@code toIndex==fromIndex}, this operation has no effect.)
1161 */
1162 protected synchronized void removeRange(int fromIndex, int toIndex) {
1163 modCount++;
1164 shiftTailOverGap(elementData, fromIndex, toIndex);
1165 }
1166
1167 /** Erases the gap from lo to hi, by sliding down following elements. */
1168 private void shiftTailOverGap(Object[] es, int lo, int hi) {
1169 System.arraycopy(es, hi, es, lo, elementCount - hi);
1170 for (int to = elementCount, i = (elementCount -= hi - lo); i < to; i++)
1171 es[i] = null;
1172 }
1173
1174 /**
1175 * Loads a {@code Vector} instance from a stream
1176 * (that is, deserializes it).
1177 * This method performs checks to ensure the consistency
1178 * of the fields.
1179 *
1180 * @param in the stream
1181 * @throws java.io.IOException if an I/O error occurs
1182 * @throws ClassNotFoundException if the stream contains data
1183 * of a non-existing class
1184 */
1185 private void readObject(ObjectInputStream in)
1186 throws IOException, ClassNotFoundException {
1187 ObjectInputStream.GetField gfields = in.readFields();
1188 int count = gfields.get("elementCount", 0);
1189 Object[] data = (Object[])gfields.get("elementData", null);
1190 if (count < 0 || data == null || count > data.length) {
1191 throw new StreamCorruptedException("Inconsistent vector internals");
1192 }
1193 elementCount = count;
1194 elementData = data.clone();
1195 }
1196
1197 /**
1198 * Saves the state of the {@code Vector} instance to a stream
1199 * (that is, serializes it).
1200 * This method performs synchronization to ensure the consistency
1201 * of the serialized data.
1202 *
1203 * @param s the stream
1204 * @throws java.io.IOException if an I/O error occurs
1205 */
1206 private void writeObject(java.io.ObjectOutputStream s)
1207 throws java.io.IOException {
1208 final java.io.ObjectOutputStream.PutField fields = s.putFields();
1209 final Object[] data;
1210 synchronized (this) {
1211 fields.put("capacityIncrement", capacityIncrement);
1212 fields.put("elementCount", elementCount);
1213 data = elementData.clone();
1214 }
1215 fields.put("elementData", data);
1216 s.writeFields();
1217 }
1218
1219 /**
1220 * Returns a list iterator over the elements in this list (in proper
1221 * sequence), starting at the specified position in the list.
1222 * The specified index indicates the first element that would be
1223 * returned by an initial call to {@link ListIterator#next next}.
1224 * An initial call to {@link ListIterator#previous previous} would
1225 * return the element with the specified index minus one.
1226 *
1227 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
1228 *
1229 * @throws IndexOutOfBoundsException {@inheritDoc}
1230 */
1231 public synchronized ListIterator<E> listIterator(int index) {
1232 if (index < 0 || index > elementCount)
1233 throw new IndexOutOfBoundsException("Index: "+index);
1234 return new ListItr(index);
1235 }
1236
1237 /**
1238 * Returns a list iterator over the elements in this list (in proper
1239 * sequence).
1240 *
1241 * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
1242 *
1243 * @see #listIterator(int)
1244 */
1245 public synchronized ListIterator<E> listIterator() {
1246 return new ListItr(0);
1247 }
1248
1249 /**
1250 * Returns an iterator over the elements in this list in proper sequence.
1251 *
1252 * <p>The returned iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
1253 *
1254 * @return an iterator over the elements in this list in proper sequence
1255 */
1256 public synchronized Iterator<E> iterator() {
1257 return new Itr();
1258 }
1259
1260 /**
1261 * An optimized version of AbstractList.Itr
1262 */
1263 private class Itr implements Iterator<E> {
1264 int cursor; // index of next element to return
1265 int lastRet = -1; // index of last element returned; -1 if no such
1266 int expectedModCount = modCount;
1267
1268 public boolean hasNext() {
1269 // Racy but within spec, since modifications are checked
1270 // within or after synchronization in next/previous
1271 return cursor != elementCount;
1272 }
1273
1274 public E next() {
1275 synchronized (Vector.this) {
1276 checkForComodification();
1277 int i = cursor;
1278 if (i >= elementCount)
1279 throw new NoSuchElementException();
1280 cursor = i + 1;
1281 return elementData(lastRet = i);
1282 }
1283 }
1284
1285 public void remove() {
1286 if (lastRet == -1)
1287 throw new IllegalStateException();
1288 synchronized (Vector.this) {
1289 checkForComodification();
1290 Vector.this.remove(lastRet);
1291 expectedModCount = modCount;
1292 }
1293 cursor = lastRet;
1294 lastRet = -1;
1295 }
1296
1297 @Override
1298 public void forEachRemaining(Consumer<? super E> action) {
1299 Objects.requireNonNull(action);
1300 synchronized (Vector.this) {
1301 final int size = elementCount;
1302 int i = cursor;
1303 if (i >= size) {
1304 return;
1305 }
1306 final Object[] es = elementData;
1307 if (i >= es.length)
1308 throw new ConcurrentModificationException();
1309 while (i < size && modCount == expectedModCount)
1310 action.accept(elementAt(es, i++));
1311 // update once at end of iteration to reduce heap write traffic
1312 cursor = i;
1313 lastRet = i - 1;
1314 checkForComodification();
1315 }
1316 }
1317
1318 final void checkForComodification() {
1319 if (modCount != expectedModCount)
1320 throw new ConcurrentModificationException();
1321 }
1322 }
1323
1324 /**
1325 * An optimized version of AbstractList.ListItr
1326 */
1327 final class ListItr extends Itr implements ListIterator<E> {
1328 ListItr(int index) {
1329 super();
1330 cursor = index;
1331 }
1332
1333 public boolean hasPrevious() {
1334 return cursor != 0;
1335 }
1336
1337 public int nextIndex() {
1338 return cursor;
1339 }
1340
1341 public int previousIndex() {
1342 return cursor - 1;
1343 }
1344
1345 public E previous() {
1346 synchronized (Vector.this) {
1347 checkForComodification();
1348 int i = cursor - 1;
1349 if (i < 0)
1350 throw new NoSuchElementException();
1351 cursor = i;
1352 return elementData(lastRet = i);
1353 }
1354 }
1355
1356 public void set(E e) {
1357 if (lastRet == -1)
1358 throw new IllegalStateException();
1359 synchronized (Vector.this) {
1360 checkForComodification();
1361 Vector.this.set(lastRet, e);
1362 }
1363 }
1364
1365 public void add(E e) {
1366 int i = cursor;
1367 synchronized (Vector.this) {
1368 checkForComodification();
1369 Vector.this.add(i, e);
1370 expectedModCount = modCount;
1371 }
1372 cursor = i + 1;
1373 lastRet = -1;
1374 }
1375 }
1376
1377 /**
1378 * @throws NullPointerException {@inheritDoc}
1379 */
1380 @Override
1381 public synchronized void forEach(Consumer<? super E> action) {
1382 Objects.requireNonNull(action);
1383 final int expectedModCount = modCount;
1384 final Object[] es = elementData;
1385 final int size = elementCount;
1386 for (int i = 0; modCount == expectedModCount && i < size; i++)
1387 action.accept(elementAt(es, i));
1388 if (modCount != expectedModCount)
1389 throw new ConcurrentModificationException();
1390 }
1391
1392 /**
1393 * @throws NullPointerException {@inheritDoc}
1394 */
1395 @Override
1396 public synchronized void replaceAll(UnaryOperator<E> operator) {
1397 Objects.requireNonNull(operator);
1398 final int expectedModCount = modCount;
1399 final Object[] es = elementData;
1400 final int size = elementCount;
1401 for (int i = 0; modCount == expectedModCount && i < size; i++)
1402 es[i] = operator.apply(elementAt(es, i));
1403 if (modCount != expectedModCount)
1404 throw new ConcurrentModificationException();
1405 modCount++;
1406 }
1407
1408 @SuppressWarnings("unchecked")
1409 @Override
1410 public synchronized void sort(Comparator<? super E> c) {
1411 final int expectedModCount = modCount;
1412 Arrays.sort((E[]) elementData, 0, elementCount, c);
1413 if (modCount != expectedModCount)
1414 throw new ConcurrentModificationException();
1415 modCount++;
1416 }
1417
1418 /**
1419 * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
1420 * and <em>fail-fast</em> {@link Spliterator} over the elements in this
1421 * list.
1422 *
1423 * <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
1424 * {@link Spliterator#SUBSIZED}, and {@link Spliterator#ORDERED}.
1425 * Overriding implementations should document the reporting of additional
1426 * characteristic values.
1427 *
1428 * @return a {@code Spliterator} over the elements in this list
1429 * @since 1.8
1430 */
1431 @Override
1432 public Spliterator<E> spliterator() {
1433 return new VectorSpliterator(null, 0, -1, 0);
1434 }
1435
1436 /** Similar to ArrayList Spliterator */
1437 final class VectorSpliterator implements Spliterator<E> {
1438 private Object[] array;
1439 private int index; // current index, modified on advance/split
1440 private int fence; // -1 until used; then one past last index
1441 private int expectedModCount; // initialized when fence set
1442
1443 /** Creates new spliterator covering the given range. */
1444 VectorSpliterator(Object[] array, int origin, int fence,
1445 int expectedModCount) {
1446 this.array = array;
1447 this.index = origin;
1448 this.fence = fence;
1449 this.expectedModCount = expectedModCount;
1450 }
1451
1452 private int getFence() { // initialize on first use
1453 int hi;
1454 if ((hi = fence) < 0) {
1455 synchronized (Vector.this) {
1456 array = elementData;
1457 expectedModCount = modCount;
1458 hi = fence = elementCount;
1459 }
1460 }
1461 return hi;
1462 }
1463
1464 public Spliterator<E> trySplit() {
1465 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1466 return (lo >= mid) ? null :
1467 new VectorSpliterator(array, lo, index = mid, expectedModCount);
1468 }
1469
1470 @SuppressWarnings("unchecked")
1471 public boolean tryAdvance(Consumer<? super E> action) {
1472 Objects.requireNonNull(action);
1473 int i;
1474 if (getFence() > (i = index)) {
1475 index = i + 1;
1476 action.accept((E)array[i]);
1477 if (modCount != expectedModCount)
1478 throw new ConcurrentModificationException();
1479 return true;
1480 }
1481 return false;
1482 }
1483
1484 @SuppressWarnings("unchecked")
1485 public void forEachRemaining(Consumer<? super E> action) {
1486 Objects.requireNonNull(action);
1487 final int hi = getFence();
1488 final Object[] a = array;
1489 int i;
1490 for (i = index, index = hi; i < hi; i++)
1491 action.accept((E) a[i]);
1492 if (modCount != expectedModCount)
1493 throw new ConcurrentModificationException();
1494 }
1495
1496 public long estimateSize() {
1497 return getFence() - index;
1498 }
1499
1500 public int characteristics() {
1501 return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
1502 }
1503 }
1504
1505 void checkInvariants() {
1506 // assert elementCount >= 0;
1507 // assert elementCount == elementData.length || elementData[elementCount] == null;
1508 }
1509 }
1510