集合类源码——Vector和Stack（1.8）

Vector：默认容量为10，可以在构造时指定扩容大小，没有指定则默认两倍扩容，方法都是synchronized的

public class Vector<E> extends AbstractList<E> implements List<E>, RandomAccess, Cloneable, java.io.Serializable {

	protected Object[] elementData;

	protected int elementCount;

	protected int capacityIncrement;

	// 默认大小为10
	public Vector() {
		this(10);
	}

	// 可以在构造时指定扩容大小
	public Vector(int initialCapacity, int capacityIncrement) {
		super();
		if (initialCapacity < 0)
			throw new IllegalArgumentException("Illegal Capacity: " + initialCapacity);
		this.elementData = new Object[initialCapacity];
		this.capacityIncrement = capacityIncrement;
	}

	// 如果没指定扩容大小，默认两倍扩容
	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);
	}

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

	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 */
	}

	public synchronized boolean add(E e) {
		modCount++;
		ensureCapacityHelper(elementCount + 1);
		elementData[elementCount++] = e;
		return true;
	}
}

Stack extends Vector, push(), pop(), peek()都是调的Vector的方法