使用Apache POI处理excel公式不更新的解决办法

private static void updateFormula(Workbook wb,Sheet s,int row){
        Row r=s.getRow(row);
        Cell c=null;
        FormulaEcaluator eval=null;
        if(wb instanceof HSSFWorkbook)
            eval=new HSSFFormulaEvaluator((HSSFWorkbook) wb);
        else if(wb instanceof XSSFWorkbook)
            eval=new XSSFFormulaEvaluator((XSSFWorkbook) wb);
        for(int i=r.getFirstCellNum();i<r.getLastCellNum();i++){
            c=r.getCell(i);
            if(c.getCellType()==Cell.CELL_TYPE_FORMULA)
                eval.evaluateFormulaCell(c);
        }
}