JDK版本
186.png
Vector簡(jiǎn)介
/**
* The {@code Vector} class implements a growable array of
* objects. Like an array, it contains components that can be
* accessed using an integer index. However, the size of a
* {@code Vector} can grow or shrink as needed to accommodate
* adding and removing items after the {@code Vector} has been created.
*
* <p>Each vector tries to optimize storage management by maintaining a
* {@code capacity} and a {@code capacityIncrement}. The
* {@code capacity} is always at least as large as the vector
* size; it is usually larger because as components are added to the
* vector, the vector's storage increases in chunks the size of
* {@code capacityIncrement}. An application can increase the
* capacity of a vector before inserting a large number of
* components; this reduces the amount of incremental reallocation.
*
* <p><a name="fail-fast">
* The iterators returned by this class's {@link #iterator() iterator} and
* {@link #listIterator(int) listIterator} methods are <em>fail-fast</em></a>:
* if the vector is structurally modified at any time after the iterator is
* created, in any way except through the iterator's own
* {@link ListIterator#remove() remove} or
* {@link ListIterator#add(Object) add} methods, the iterator will throw a
* {@link ConcurrentModificationException}. Thus, in the face of
* concurrent modification, the iterator fails quickly and cleanly, rather
* than risking arbitrary, non-deterministic behavior at an undetermined
* time in the future. The {@link Enumeration Enumerations} returned by
* the {@link #elements() elements} method are <em>not</em> fail-fast.
*
* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
* as it is, generally speaking, impossible to make any hard guarantees in the
* presence of unsynchronized concurrent modification. Fail-fast iterators
* throw {@code ConcurrentModificationException} on a best-effort basis.
* Therefore, it would be wrong to write a program that depended on this
* exception for its correctness: <i>the fail-fast behavior of iterators
* should be used only to detect bugs.</i>
*
* <p>As of the Java 2 platform v1.2, this class was retrofitted to
* implement the {@link List} interface, making it a member of the
* <a href="{@docRoot}/../technotes/guides/collections/index.html">
* Java Collections Framework</a>. Unlike the new collection
* implementations, {@code Vector} is synchronized. If a thread-safe
* implementation is not needed, it is recommended to use {@link
* ArrayList} in place of {@code Vector}.
*
* @author Lee Boynton
* @author Jonathan Payne
* @see Collection
* @see LinkedList
* @since JDK1.0
*/
首先，Vector 是一個(gè)可增長(zhǎng)的數(shù)組（和 ArrayList 類似）声怔，能夠用索引直接找到元素跛锌，Vector 的容量可增可減
其次惠爽，Vector 使用變量 capacity 和 capacityIncrement 來進(jìn)行容量的管理添吗，關(guān)于容量和大小的說法沥曹，之前也提到過，容量是最多能夠容納多少元素碟联，而大小是目前容納了多少元素妓美。capacity 指的就是容量，是永遠(yuǎn)大于或等于 Vector 的大小的鲤孵，不過容量通常是大于 Vector 的大小的壶栋，因?yàn)樗鼣U(kuò)容的方式有點(diǎn)特殊，下文提及普监，在插入大量數(shù)據(jù)之前贵试，最好能進(jìn)行適當(dāng)?shù)臄U(kuò)容，避免了再分配的時(shí)間浪費(fèi)
Vector 是線程安全的鹰椒，它所有的方法都加上了 synchronized 關(guān)鍵字锡移。
源碼分析
package java.util;
public class Vector<E>
extends AbstractList<E>
implements List<E>, RandomAccess, Cloneable, java.io.Serializable
{
//保存Vector中的數(shù)據(jù)的數(shù)組
protected Object[] elementData;
// 實(shí)際數(shù)據(jù)的長(zhǎng)度
protected int elementCount;
//容量增長(zhǎng)系數(shù)
protected int capacityIncrement;
/** use serialVersionUID from JDK 1.0.2 for interoperability */
//Vector的版本序號(hào)
private static final long serialVersionUID = -2767605614048989439L;
// Vector有參構(gòu)造函數(shù)，指定Vector“容量大小”和“增長(zhǎng)系數(shù)”的構(gòu)造函數(shù)
public Vector(int initialCapacity, int capacityIncrement) {
super();
if (initialCapacity < 0)
throw new IllegalArgumentException("Illegal Capacity: "+
//新建一個(gè)數(shù)組漆际，數(shù)組容量是initialCapacity initialCapacity);
this.elementData = new Object[initialCapacity];
//設(shè)置容量增長(zhǎng)系數(shù)
this.capacityIncrement = capacityIncrement;
}
// Vector有參構(gòu)造函數(shù)，容量大小的構(gòu)造函數(shù)
public Vector(int initialCapacity) {
this(initialCapacity, 0);
}
//Vector無參構(gòu)造函數(shù)夺饲，默認(rèn)容量為10
public Vector() {
this(10);
}
//Vector有參構(gòu)造函數(shù)奸汇，指定集合的Vector構(gòu)造函數(shù)
public Vector(Collection<? extends E> c) {
//獲取“集合(c)”的數(shù)組，并將其賦值給elementData
elementData = c.toArray();
//設(shè)置數(shù)組長(zhǎng)度
elementCount = elementData.length;
// c.toArray might (incorrectly) not return Object[] (see 6260652)
if (elementData.getClass() != Object[].class)
elementData = Arrays.copyOf(elementData, elementCount, Object[].class);
}
// 將數(shù)組Vector的全部元素都拷貝到數(shù)組anArray中
public synchronized void copyInto(Object[] anArray) {
System.arraycopy(elementData, 0, anArray, 0, elementCount);
}
// 將當(dāng)前容量值設(shè)為 = 實(shí)際元素個(gè)數(shù)
public synchronized void trimToSize() {
modCount++;
int oldCapacity = elementData.length;
if (elementCount < oldCapacity) {
elementData = Arrays.copyOf(elementData, elementCount);
}
}
// 確定Vector的容量
public synchronized void ensureCapacity(int minCapacity) {
if (minCapacity > 0) {
modCount++;
ensureCapacityHelper(minCapacity);
}
}
private void ensureCapacityHelper(int minCapacity) {
// overflow-conscious code
if (minCapacity - elementData.length > 0)
grow(minCapacity);
}
//設(shè)置最大數(shù)組長(zhǎng)度
private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
private void grow(int minCapacity) {
// overflow-conscious code
int oldCapacity = elementData.length;
int newCapacity = oldCapacity + ((capacityIncrement > 0) ?
capacityIncrement : oldCapacity);
if (newCapacity - minCapacity < 0)
newCapacity = minCapacity;
if (newCapacity - MAX_ARRAY_SIZE > 0)
newCapacity = hugeCapacity(minCapacity);
elementData = Arrays.copyOf(elementData, newCapacity);
}
private static int hugeCapacity(int minCapacity) {
if (minCapacity < 0) // overflow
throw new OutOfMemoryError();
return (minCapacity > MAX_ARRAY_SIZE) ?
Integer.MAX_VALUE :
MAX_ARRAY_SIZE;
}
// 設(shè)置容量值為 newSize
public synchronized void setSize(int newSize) {
modCount++;
if (newSize > elementCount) {
// 若 "newSize 大于 Vector容量"往声，則調(diào)整Vector的大小擂找。
ensureCapacityHelper(newSize);
} else {
// 若 "newSize 小于/等于 Vector容量"，則將newSize位置開始的元素都設(shè)置為null
for (int i = newSize ; i < elementCount ; i++) {
elementData[i] = null;
}
}
elementCount = newSize;
}
// 返回“Vector的總的容量”
public synchronized int capacity() {
return elementData.length;
}
// 返回“Vector的實(shí)際大小”浩销，即Vector中元素個(gè)數(shù)
public synchronized int size() {
return elementCount;
}
// 判斷Vector是否為空
public synchronized boolean isEmpty() {
return elementCount == 0;
}
// 返回“Vector中全部元素對(duì)應(yīng)的Enumeration”
public Enumeration<E> elements() {
// 通過匿名類實(shí)現(xiàn)Enumeration
return new Enumeration<E>() {
int count = 0;
// 是否存在下一個(gè)元素
public boolean hasMoreElements() {
return count < elementCount;
}
// 獲取下一個(gè)元素
public E nextElement() {
synchronized (Vector.this) {
if (count < elementCount) {
return elementData(count++);
}
}
throw new NoSuchElementException("Vector Enumeration");
}
};
}
// 返回Vector中是否包含對(duì)象(o)
public boolean contains(Object o) {
return indexOf(o, 0) >= 0;
}
/**
* Returns the index of the first occurrence of the specified element
* in this vector, or -1 if this vector does not contain the element.
* More formally, returns the lowest index {@code i} such that
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
* or -1 if there is no such index.
*
* @param o element to search for
* @return the index of the first occurrence of the specified element in
* this vector, or -1 if this vector does not contain the element
*/
public int indexOf(Object o) {
return indexOf(o, 0);
}
// 從index位置開始向后查找元素(o)贯涎。
// 若找到，則返回元素的索引值慢洋；否則塘雳，返回-1
public synchronized int indexOf(Object o, int index) {
if (o == null) {
// 若查找元素為null，則正向找出null元素普筹，并返回它對(duì)應(yīng)的序號(hào)
for (int i = index ; i < elementCount ; i++)
if (elementData[i]==null)
return i;
} else {
// 若查找元素不為null败明，則正向找出該元素，并返回它對(duì)應(yīng)的序號(hào)
for (int i = index ; i < elementCount ; i++)
if (o.equals(elementData[i]))
return i;
}
return -1;
}
// 從后向前查找元素(o)太防。并返回元素的索引
public synchronized int lastIndexOf(Object o) {
return lastIndexOf(o, elementCount-1);
}
// 從后向前查找元素(o)妻顶。開始位置是從前向后的第index個(gè)數(shù)；
// 若找到，則返回元素的“索引值”讳嘱；否則幔嗦，返回-1。
public synchronized int lastIndexOf(Object o, int index) {
if (index >= elementCount)
throw new IndexOutOfBoundsException(index + " >= "+ elementCount);
if (o == null) {
// 若查找元素為null沥潭，則反向找出null元素邀泉，并返回它對(duì)應(yīng)的序號(hào)
for (int i = index; i >= 0; i--)
if (elementData[i]==null)
return i;
} else {
// 若查找元素不為null，則反向找出該元素叛氨，并返回它對(duì)應(yīng)的序號(hào)
for (int i = index; i >= 0; i--)
if (o.equals(elementData[i]))
return i;
}
return -1;
}
// 返回Vector中index位置的元素呼渣。
// 若index月結(jié)，則拋出異常
public synchronized E elementAt(int index) {
if (index >= elementCount) {
throw new ArrayIndexOutOfBoundsException(index + " >= " + elementCount);
}
return elementData(index);
}
// 獲取Vector中的第一個(gè)元素寞埠。
// 若失敗屁置，則拋出異常！
public synchronized E firstElement() {
if (elementCount == 0) {
throw new NoSuchElementException();
}
return elementData(0);
}
// 獲取Vector中的最后一個(gè)元素仁连。
// 若失敗蓝角，則拋出異常！
public synchronized E lastElement() {
if (elementCount == 0) {
throw new NoSuchElementException();
}
return elementData(elementCount - 1);
}
// 設(shè)置index位置的元素值為obj
public synchronized void setElementAt(E obj, int index) {
if (index >= elementCount) {
throw new ArrayIndexOutOfBoundsException(index + " >= " +
elementCount);
}
elementData[index] = obj;
}
// 刪除index位置的元素
public synchronized void removeElementAt(int index) {
modCount++;
if (index >= elementCount) {
throw new ArrayIndexOutOfBoundsException(index + " >= " +
elementCount);
}
else if (index < 0) {
throw new ArrayIndexOutOfBoundsException(index);
}
int j = elementCount - index - 1;
if (j > 0) {
System.arraycopy(elementData, index + 1, elementData, index, j);
}
elementCount--;
elementData[elementCount] = null; /* to let gc do its work */
}
// 在index位置處插入元素(obj)
public synchronized void insertElementAt(E obj, int index) {
modCount++;
if (index > elementCount) {
throw new ArrayIndexOutOfBoundsException(index
+ " > " + elementCount);
}
ensureCapacityHelper(elementCount + 1);
System.arraycopy(elementData, index, elementData, index + 1, elementCount - index);
elementData[index] = obj;
elementCount++;
}
// 將“元素obj”添加到Vector末尾
public synchronized void addElement(E obj) {
modCount++;
ensureCapacityHelper(elementCount + 1);
elementData[elementCount++] = obj;
}
// 在Vector中查找并刪除元素obj饭冬。
// 成功的話使鹅，返回true；否則昌抠，返回false患朱。
public synchronized boolean removeElement(Object obj) {
modCount++;
int i = indexOf(obj);
if (i >= 0) {
removeElementAt(i);
return true;
}
return false;
}
// 刪除Vector中的全部元素
public synchronized void removeAllElements() {
modCount++;
// Let gc do its work
// 將Vector中的全部元素設(shè)為null
for (int i = 0; i < elementCount; i++)
elementData[i] = null;
elementCount = 0;
}
//@SuppressWarnings注解用于抑制編譯器產(chǎn)生警告信息。
// 克隆函數(shù)
public synchronized Object clone() {
try {
@SuppressWarnings("unchecked")
Vector<E> v = (Vector<E>) super.clone();
// 將當(dāng)前Vector的全部元素拷貝到v中
v.elementData = Arrays.copyOf(elementData, elementCount);
v.modCount = 0;
return v;
} catch (CloneNotSupportedException e) {
// this shouldn't happen, since we are Cloneable
throw new InternalError(e);
}
}
// 返回Object數(shù)組
public synchronized Object[] toArray() {
return Arrays.copyOf(elementData, elementCount);
}
// 返回Vector的模板數(shù)組炊苫。所謂模板數(shù)組裁厅，即可以將T設(shè)為任意的數(shù)據(jù)類型
@SuppressWarnings("unchecked")
public synchronized <T> T[] toArray(T[] a) {
// 若數(shù)組a的大小 < Vector的元素個(gè)數(shù)；
// 則新建一個(gè)T[]數(shù)組侨艾，數(shù)組大小是“Vector的元素個(gè)數(shù)”执虹，并將“Vector”全部拷貝到新數(shù)組中
if (a.length < elementCount)
return (T[]) Arrays.copyOf(elementData, elementCount, a.getClass());
// 若數(shù)組a的大小 >= Vector的元素個(gè)數(shù)；
// 則將Vector的全部元素都拷貝到數(shù)組a中唠梨。
System.arraycopy(elementData, 0, a, 0, elementCount);
if (a.length > elementCount)
a[elementCount] = null;
return a;
}
// Positional Access Operations
@SuppressWarnings("unchecked")
E elementData(int index) {
return (E) elementData[index];
}
// 獲取index位置的元素
public synchronized E get(int index) {
if (index >= elementCount)
throw new ArrayIndexOutOfBoundsException(index);
return elementData(index);
}
// 設(shè)置index位置的值為element袋励。并返回index位置的原始值
public synchronized E set(int index, E element) {
if (index >= elementCount)
throw new ArrayIndexOutOfBoundsException(index);
E oldValue = elementData(index);
elementData[index] = element;
return oldValue;
}
// 將“元素e”添加到Vector最后。
public synchronized boolean add(E e) {
modCount++;
ensureCapacityHelper(elementCount + 1);
elementData[elementCount++] = e;
return true;
}
// 刪除Vector中的元素o
public boolean remove(Object o) {
return removeElement(o);
}
// 在index位置添加元素element
public void add(int index, E element) {
insertElementAt(element, index);
}
// 刪除index位置的元素当叭，并返回index位置的原始值
public synchronized E remove(int index) {
modCount++;
if (index >= elementCount)
throw new ArrayIndexOutOfBoundsException(index);
E oldValue = elementData(index);
int numMoved = elementCount - index - 1;
if (numMoved > 0)
System.arraycopy(elementData, index+1, elementData, index,
numMoved);
elementData[--elementCount] = null; // Let gc do its work
return oldValue;
}
// 清空Vector
public void clear() {
removeAllElements();
}
// Bulk Operations
// 返回Vector是否包含集合c
public synchronized boolean containsAll(Collection<?> c) {
return super.containsAll(c);
}
// 將集合c添加到Vector中
public synchronized boolean addAll(Collection<? extends E> c) {
modCount++;
Object[] a = c.toArray();
int numNew = a.length;
ensureCapacityHelper(elementCount + numNew);
// 將集合c的全部元素拷貝到數(shù)組elementData中
System.arraycopy(a, 0, elementData, elementCount, numNew);
elementCount += numNew;
return numNew != 0;
}
// 刪除集合c的全部元素
public synchronized boolean removeAll(Collection<?> c) {
return super.removeAll(c);
}
// 刪除“非集合c中的元素”
public synchronized boolean retainAll(Collection<?> c) {
return super.retainAll(c);
}
// 從index位置開始茬故，將集合c添加到Vector中
public synchronized boolean addAll(int index, Collection<? extends E> c) {
modCount++;
if (index < 0 || index > elementCount)
throw new ArrayIndexOutOfBoundsException(index);
Object[] a = c.toArray();
int numNew = a.length;
ensureCapacityHelper(elementCount + numNew);
int numMoved = elementCount - index;
if (numMoved > 0)
System.arraycopy(elementData, index, elementData, index + numNew,
numMoved);
System.arraycopy(a, 0, elementData, index, numNew);
elementCount += numNew;
return numNew != 0;
}
// 返回兩個(gè)對(duì)象是否相等
public synchronized boolean equals(Object o) {
return super.equals(o);
}
// 計(jì)算哈希值
public synchronized int hashCode() {
return super.hashCode();
}
// 調(diào)用父類的toString()
public synchronized String toString() {
return super.toString();
}
// 獲取Vector中fromIndex(包括)到toIndex(不包括)的子集
public synchronized List<E> subList(int fromIndex, int toIndex) {
return Collections.synchronizedList(super.subList(fromIndex, toIndex),
this);
}
// 刪除Vector中fromIndex到toIndex的元素
protected synchronized void removeRange(int fromIndex, int toIndex) {
modCount++;
int numMoved = elementCount - toIndex;
System.arraycopy(elementData, toIndex, elementData, fromIndex,
numMoved);
// Let gc do its work
int newElementCount = elementCount - (toIndex-fromIndex);
while (elementCount != newElementCount)
elementData[--elementCount] = null;
}
//從文件中讀取數(shù)據(jù)，放到Vector中
private void readObject(ObjectInputStream in)
throws IOException, ClassNotFoundException {
ObjectInputStream.GetField gfields = in.readFields();
int count = gfields.get("elementCount", 0);
Object[] data = (Object[])gfields.get("elementData", null);
if (count < 0 || data == null || count > data.length) {
throw new StreamCorruptedException("Inconsistent vector internals");
}
elementCount = count;
elementData = data.clone();
}
// java.io.Serializable的寫入函數(shù)
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
final java.io.ObjectOutputStream.PutField fields = s.putFields();
final Object[] data;
synchronized (this) {
fields.put("capacityIncrement", capacityIncrement);
fields.put("elementCount", elementCount);
data = elementData.clone();
}
fields.put("elementData", data);
s.writeFields();
}
//ListInterator迭代器
public synchronized ListIterator<E> listIterator(int index) {
if (index < 0 || index > elementCount)
throw new IndexOutOfBoundsException("Index: "+index);
return new ListItr(index);
}
public synchronized ListIterator<E> listIterator() {
return new ListItr(0);
}
//迭代器
public synchronized Iterator<E> iterator() {
return new Itr();
}
//迭代器內(nèi)部類
private class Itr implements Iterator<E> {
int cursor; // index of next element to return
int lastRet = -1; // index of last element returned; -1 if no such
int expectedModCount = modCount;
public boolean hasNext() {
// Racy but within spec, since modifications are checked
// within or after synchronization in next/previous
return cursor != elementCount;
}
public E next() {
synchronized (Vector.this) {
checkForComodification();
int i = cursor;
if (i >= elementCount)
throw new NoSuchElementException();
cursor = i + 1;
return elementData(lastRet = i);
}
}
public void remove() {
if (lastRet == -1)
throw new IllegalStateException();
synchronized (Vector.this) {
checkForComodification();
Vector.this.remove(lastRet);
expectedModCount = modCount;
}
cursor = lastRet;
lastRet = -1;
}
@Override
public void forEachRemaining(Consumer<? super E> action) {
Objects.requireNonNull(action);
synchronized (Vector.this) {
final int size = elementCount;
int i = cursor;
if (i >= size) {
return;
}
@SuppressWarnings("unchecked")
final E[] elementData = (E[]) Vector.this.elementData;
if (i >= elementData.length) {
throw new ConcurrentModificationException();
}
while (i != size && modCount == expectedModCount) {
action.accept(elementData[i++]);
}
// update once at end of iteration to reduce heap write traffic
cursor = i;
lastRet = i - 1;
checkForComodification();
}
}
final void checkForComodification() {
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
}
}
/**
* An optimized version of AbstractList.ListItr
*/
final class ListItr extends Itr implements ListIterator<E> {
ListItr(int index) {
super();
cursor = index;
}
public boolean hasPrevious() {
return cursor != 0;
}
public int nextIndex() {
return cursor;
}
public int previousIndex() {
return cursor - 1;
}
public E previous() {
synchronized (Vector.this) {
checkForComodification();
int i = cursor - 1;
if (i < 0)
throw new NoSuchElementException();
cursor = i;
return elementData(lastRet = i);
}
}
public void set(E e) {
if (lastRet == -1)
throw new IllegalStateException();
synchronized (Vector.this) {
checkForComodification();
Vector.this.set(lastRet, e);
}
}
public void add(E e) {
int i = cursor;
synchronized (Vector.this) {
checkForComodification();
Vector.this.add(i, e);
expectedModCount = modCount;
}
cursor = i + 1;
lastRet = -1;
}
}
@Override
public synchronized void forEach(Consumer<? super E> action) {
Objects.requireNonNull(action);
final int expectedModCount = modCount;
@SuppressWarnings("unchecked")
final E[] elementData = (E[]) this.elementData;
final int elementCount = this.elementCount;
for (int i=0; modCount == expectedModCount && i < elementCount; i++) {
action.accept(elementData[i]);
}
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
}
@Override
@SuppressWarnings("unchecked")
public synchronized boolean removeIf(Predicate<? super E> filter) {
Objects.requireNonNull(filter);
// figure out which elements are to be removed
// any exception thrown from the filter predicate at this stage
// will leave the collection unmodified
int removeCount = 0;
final int size = elementCount;
final BitSet removeSet = new BitSet(size);
final int expectedModCount = modCount;
for (int i=0; modCount == expectedModCount && i < size; i++) {
@SuppressWarnings("unchecked")
final E element = (E) elementData[i];
if (filter.test(element)) {
removeSet.set(i);
removeCount++;
}
}
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
// shift surviving elements left over the spaces left by removed elements
final boolean anyToRemove = removeCount > 0;
if (anyToRemove) {
final int newSize = size - removeCount;
for (int i=0, j=0; (i < size) && (j < newSize); i++, j++) {
i = removeSet.nextClearBit(i);
elementData[j] = elementData[i];
}
for (int k=newSize; k < size; k++) {
elementData[k] = null; // Let gc do its work
}
elementCount = newSize;
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
modCount++;
}
return anyToRemove;
}
@Override
@SuppressWarnings("unchecked")
public synchronized void replaceAll(UnaryOperator<E> operator) {
Objects.requireNonNull(operator);
final int expectedModCount = modCount;
final int size = elementCount;
for (int i=0; modCount == expectedModCount && i < size; i++) {
elementData[i] = operator.apply((E) elementData[i]);
}
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
modCount++;
}
@SuppressWarnings("unchecked")
@Override
public synchronized void sort(Comparator<? super E> c) {
final int expectedModCount = modCount;
Arrays.sort((E[]) elementData, 0, elementCount, c);
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
modCount++;
}
/**
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
* and <em>fail-fast</em> {@link Spliterator} over the elements in this
* list.
*
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
* {@link Spliterator#SUBSIZED}, and {@link Spliterator#ORDERED}.
* Overriding implementations should document the reporting of additional
* characteristic values.
*
* @return a {@code Spliterator} over the elements in this list
* @since 1.8
*/
@Override
public Spliterator<E> spliterator() {
return new VectorSpliterator<>(this, null, 0, -1, 0);
}
/** Similar to ArrayList Spliterator */
static final class VectorSpliterator<E> implements Spliterator<E> {
private final Vector<E> list;
private Object[] array;
private int index; // current index, modified on advance/split
private int fence; // -1 until used; then one past last index
private int expectedModCount; // initialized when fence set
/** Create new spliterator covering the given range */
VectorSpliterator(Vector<E> list, Object[] array, int origin, int fence,
int expectedModCount) {
this.list = list;
this.array = array;
this.index = origin;
this.fence = fence;
this.expectedModCount = expectedModCount;
}
private int getFence() { // initialize on first use
int hi;
if ((hi = fence) < 0) {
synchronized(list) {
array = list.elementData;
expectedModCount = list.modCount;
hi = fence = list.elementCount;
}
}
return hi;
}
public Spliterator<E> trySplit() {
int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
return (lo >= mid) ? null :
new VectorSpliterator<E>(list, array, lo, index = mid,
expectedModCount);
}
@SuppressWarnings("unchecked")
public boolean tryAdvance(Consumer<? super E> action) {
int i;
if (action == null)
throw new NullPointerException();
if (getFence() > (i = index)) {
index = i + 1;
action.accept((E)array[i]);
if (list.modCount != expectedModCount)
throw new ConcurrentModificationException();
return true;
}
return false;
}
@SuppressWarnings("unchecked")
public void forEachRemaining(Consumer<? super E> action) {
int i, hi; // hoist accesses and checks from loop
Vector<E> lst; Object[] a;
if (action == null)
throw new NullPointerException();
if ((lst = list) != null) {
if ((hi = fence) < 0) {
synchronized(lst) {
expectedModCount = lst.modCount;
a = array = lst.elementData;
hi = fence = lst.elementCount;
}
}
else
a = array;
if (a != null && (i = index) >= 0 && (index = hi) <= a.length) {
while (i < hi)
action.accept((E) a[i++]);
if (lst.modCount == expectedModCount)
return;
}
}
throw new ConcurrentModificationException();
}
public long estimateSize() {
return (long) (getFence() - index);
}
public int characteristics() {
return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
}
}
}
