详解Java中的Vector

//Vector存放的元素,初始化默认长度为10protected Object[] elementData;//元素个数protected int elementCount;//每次扩容大小,默认为0protected 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;}

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;}

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;}

public synchronized boolean isEmpty() {  return elementCount == 0;}

public synchronized void setElementAt(E obj, int index) {  if (index >= elementCount) {    throw new ArrayIndexOutOfBoundsException(index + " >= " +                         elementCount);  }  elementData[index] = obj;}

 public synchronized void addElement(E obj) {  modCount++;  ensureCapacityHelper(elementCount + 1);  elementData[elementCount++] = 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++;}

public synchronized boolean removeElement(Object obj) {  modCount++;  int i = indexOf(obj);  if (i >= 0) {    removeElementAt(i);    return true;  }  return false;}