vector.md

Vector 与ArrayList类似

*. 每个方法上都有synchronized关键字 *. 扩容方式有个扩展因子capacityIncrement，即如果有扩展因子扩容容量为oldCapacity+capacityIncrement，否则为oldCapacity的2倍

Vector扩容容量机制

int newCapacity = oldCapacity + ((capacityIncrement > 0) ?
                                         capacityIncrement : oldCapacity);

Vector 添加元素源码

public synchronized boolean add(E e) {
    modCount++;
    ensureCapacityHelper(elementCount + 1);
    elementData[elementCount++] = e;
    return true;
}
private void ensureCapacityHelper(int minCapacity) {
    // overflow-conscious code
    if (minCapacity - elementData.length > 0)
        grow(minCapacity);
}
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);
}