关于文件夹的操作类，包括删除文件夹（可以直接删除其子目录与文件），获取文件夹文件列表，判断文件与文件夹是否存在，获取文件大小-Operation on the folder categories, including the deletion of folders (can be removed from the subdirectory and file), access to the folder list of files, documents and folders to determine the existence of, access to the file size, etc.