public static boolean isNumeric(String str) {    for (int i = 0; i < str.length(); i++) {        if (!Character.isDigit(str.charAt(i))) {            return false;        }    }    return true;}public static List<List<String>> readXlsx(String path) throws Exception {    InputStream is = new FileInputStream(path);    @SuppressWarnings("resource")    XSSFWorkbook xssfWorkbook = new XSSFWorkbook(is);    List<List<String>> result = new ArrayList<>();    for (int sheetIx = 0; sheetIx < xssfWorkbook.getNumberOfSheets(); sheetIx++) {        XSSFSheet xssfSheet = xssfWorkbook.getSheetAt(sheetIx);        if (xssfSheet == null)            continue;        for (int rowNum = 1; rowNum <= xssfSheet.getLastRowNum(); rowNum++) {            XSSFRow xssfRow = xssfSheet.getRow(rowNum);            int minColIx = xssfRow.getFirstCellNum();            int maxColIx = xssfRow.getLastCellNum();            List<String> rowList = new ArrayList<>();            for (int colIx = minColIx; colIx < maxColIx; colIx++) {                XSSFCell cell = xssfRow.getCell(colIx);                if (cell == null)                    continue;                rowList.add(cell.toString());            }            result.add(rowList);        }    }    return result;}