尝试写入excel时获取NULL指针

Question

这是我的Util功能：

// Method to write into an XL
public static void writeXL(String fPath, String fSheet, String[][] xData) throws Exception{

        File outFile = new File(fPath);
        HSSFWorkbook wb = new HSSFWorkbook();
        HSSFSheet osheet = wb.createSheet(fSheet);
        int xR_TS = xData.length;
      //  System.out.println(xR_TS);
        int xC_TS = xData[0].length;
      //  System.out.println(xC_TS);
        for (int myrow = 0; myrow < xR_TS; myrow++) {
            HSSFRow row = osheet.createRow(myrow);
            for (int mycol = 0; mycol < xC_TS; mycol++) {
                HSSFCell cell = row.createCell(mycol);
                cell.setCellType(HSSFCell.CELL_TYPE_STRING);
                cell.setCellValue(xData[myrow][mycol]);
            }
            FileOutputStream fOut = new FileOutputStream(outFile);
            wb.write(fOut);
            fOut.flush();
            fOut.close();
        }
    }

我正在尝试使用以下命令写入此excel：

// i is the loop value

xlActualTot[i][5]=PayAmt; // where PayAmt is the value I am capturing from website and storing it in xlActualTot[0][5] (type is String[][])

Utils.writeXL("<filepath>","TestData",xlActualTot);

我在＆＃34; xlActualTot [0] [5] = PayAmt＆＃34;这一行：
显示java.lang.NullPointerException

你能告诉我为什么会收到这个错误吗？