Array List insert operation

arrayListInsert.hpp

/**
 * Insert an element to the data structure at a specified index.
 *
 * @tparam T type
 * @param item item to insert
 * @param index index at which to insert
 */
template<typename T>
void ArrayList<T>::insert(const T &item, const int index) {
    if (index < 0 || index >= _size) {
        // If the index is out of bounds, throw an exception.
        throw std::invalid_argument("Index out of bounds");
    } else {
        // Check if there's a need to make additional space.
        if (_size >= _capacity) {
            resize();
        }

        // Increase the size of the data structure.
        // Note: It's important to do this here, before the for-loop
        // below, because the loop needs to shift some elements with one
        // position to the right.
        ++_size;

        // Shift all elements from the end down to the provided index
        // with one position to the right.
        for (int i = _size - 1; i > index; --i) {
            _array[i] = _array[i - 1];
        }

        // Assign the new element.
        _array[index] = item;
    }
}