java 設置Excle導出數字格式

import jxl.Workbook;
import jxl.WorkbookSettings;
import jxl.write.*;
import jxl.write.Number;

WorkbookSettings settings = new WorkbookSettings();
settings.setGCDisabled(true); // 關閉GC
WritableWorkbook workbook = Workbook.createWorkbook(os, settings);
WritableSheet sheet = workbook.createSheet("Sheet1", 0);

NumberFormat nf = new NumberFormat("#0.00");    //設置數字格式
WritableCellFormat wcfN = new WritableCellFormat(nf); //設置表單格式


// 若值爲空，輸出單元格格式爲普通字符串，否則輸出數字格式的單元格
sheet.addCell(StringUtils.isBlank(ObjectUtils.toString(dto.getFreight())) ?
                            new Label(index++, i, ObjectUtils.toString(dto.getFreight())) : createCell(index++, i, ObjectUtils.toString(dto.getFreight()), wcfN));
                    

設置數字格式的單元格   
 private Number createCell (int index, int i, String val, WritableCellFormat wcfN) {

//        NumberFormat nf = new NumberFormat("#0.00");    //設置數字格式
//        WritableCellFormat wcfN = new WritableCellFormat(nf); //設置表單格式
        Number labelNF = new Number(index, i, Double.parseDouble(val), wcfN); //格式化數值

        return labelNF;
    }