ArrayList底层的动态数组怎么实现？

没有动态，最终还是数组复制，小数组换大数组

//这是数据扩充的核心代码，最终就是arrays.copyof
 private void grow(int minCapacity) {
         // overflow-conscious code
         int oldCapacity = elementData.length;
         int newCapacity = oldCapacity + (oldCapacity >> 1);
         if (newCapacity - minCapacity < 0)
             newCapacity = minCapacity;
         if (newCapacity - MAX_ARRAY_SIZE > 0)
             newCapacity = hugeCapacity(minCapacity);
         // minCapacity is usually close to size, so this is a win:
         elementData = Arrays.copyOf(elementData, newCapacity);
     }