泛型转换

public <H, T> String exportShippingDocument(int sheetNum,List<H> head, List<T> list, String fileName, String tname) {

 for (T el : list) {
                    if (el instanceof ShippingDocumentsListDto) {
                        ShippingDocumentsListDto item = (ShippingDocumentsListDto)el;
                    }
                }
}