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);
= new Object[initialCapacity];
= capacityIncrement;
}
//构造函数,Collection集合
public Vector(Collection extends E> c) {
elementData = ();
elementCount = ;
if (() != Object[].class)
elementData = (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 - > 0)
grow(minCapacity);
}
//扩容
private void grow(int minCapacity) {
int oldCapacity = ;
//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 = (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) {
(elementData, 0, anArray, 0, elementCount);
}
public synchronized void trimToSize() {
modCount++;
int oldCapacity = ;
if (elementCount < oldCapacity) {
elementData = (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 ((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);
(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我网站的支持！