Vector实现了AbstractList抽象类和List接口,和ArrayList一样是基于Array存储的

Vector 是线程安全的,在大多数方法上存在synchronized关键字

//Vector存放的元素,初始化默认长度为10

protected Object[] elementData;

//元素个数

protected int elementCount;

//每次扩容大小,默认为0

protected int capacityIncrement;

//构造函数，无指定初始化大小和无扩容大小

public Vector() {

this(10);

}

//构造函数，指定初始化大小和无扩容大小

public Vector(int initialCapacity) {

this(initialCapacity, 0);

}

//构造函数，指定初始化大小和扩容大小

public Vector(int initialCapacity, int capacityIncrement) {

super();

if (initialCapacity < 0)

throw new IllegalArgumentException("Illegal Capacity: "+

initialCapacity);

this.elementData = new Object[initialCapacity];

this.capacityIncrement = capacityIncrement;

}

//构造函数,Collection集合

public Vector(Collection extends E> c) {

elementData = c.toArray();

elementCount = elementData.length;

if (elementData.getClass() != Object[].class)

elementData = Arrays.copyOf(elementData, elementCount, Object[].class);

}

//确保扩容的最小容量

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);

}

//扩容

private void grow(int minCapacity) {

int oldCapacity = elementData.length;

//当扩容大小为0的时候,扩容为原来的2倍

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;

}

ensureCapacity(int minCapacity)方法确保Vector的最小长度,当扩容2倍小于minCapacity时,扩容到minCapacity大小,minCapacity不能小于0

最大长度为2的31次方-1

设置大小

public synchronized void setSize(int newSize) {

modCount++;

if (newSize > elementCount) {

ensureCapacityHelper(newSize);

} else {

for (int i = newSize ; i < elementCount ; i++) {

elementData[i] = null;

}

}

elementCount = newSize;

}

超过大小的被设置为Null

public synchronized void copyInto(Object[] anArray) {

System.arraycopy(elementData, 0, anArray, 0, elementCount);

}

public synchronized void trimToSize() {

modCount++;

int oldCapacity = elementData.length;

if (elementCount < oldCapacity) {

elementData = Arrays.copyOf(elementData, elementCount);

}

}

public synchronized int indexOf(Object o, int index) {

if (o == null) {

for (int i = index ; i < elementCount ; i++)

if (elementData[i]==null)

return i;

} else {

for (int i = index ; i < elementCount ; i++)

if (o.equals(elementData[i]))

return i;

}

return -1;

}

是否为空

public synchronized boolean isEmpty() {

return elementCount == 0;

}

设置索引上的元素

public synchronized void setElementAt(E obj, int index) {

if (index >= elementCount) {

throw new ArrayIndexOutOfBoundsException(index + " >= " +

elementCount);

}

elementData[index] = obj;

}

添加元素

public synchronized void addElement(E obj) {

modCount++;

ensureCapacityHelper(elementCount + 1);

elementData[elementCount++] = obj;

}

扩容

插入元素

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++;

}

扩容

数组拷贝向索引后移动

删除为向前移动

删除元素

public synchronized boolean removeElement(Object obj) {

modCount++;

int i = indexOf(obj);

if (i >= 0) {

removeElementAt(i);

return true;

}

return false;

}

只能删除第一个

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详解

以上所述是小编给大家介绍的Java中的Vector，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对脚本之家网站的支持！