Package should contain a content type part [M1.13]

public static Workbook create(InputStream in) throws     
    IOException,InvalidFormatException {
        if (!in.markSupported()) {
            in = new PushbackInputStream(in, 8);
        }
        if (POIFSFileSystem.hasPOIFSHeader(in)) {
            return new HSSFWorkbook(in);
        }
        if (POIXMLDocument.hasOOXMLHeader(in)) {
            return new XSSFWorkbook(OPCPackage.open(in));
        }
        throw new IllegalArgumentException("你的excel版本目前poi解析不了");

    }

讀寫xls和xlsx格式時，HSSFWorkbook針對xls，XSSFWorkbook針對xlsx