java POI 修改Excel2007时候的方法。

读取的方法很简单

public class ReadExcelPOI {

    public void readExcel() {
        try {

            String fileName = "E:\\xxx\\xxx\\a.xlsx";
            XSSFWorkbook xwb = new XSSFWorkbook(fileName);
            // 循环工作表Sheet
            for (int numSheet = 0; numSheet < xwb.getNumberOfSheets(); numSheet++) {
                XSSFSheet xSheet = xwb.getSheetAt(numSheet);
                if (xSheet == null) {
                    continue;
                }

                // 循环行Row
                for (int rowNum = 0; rowNum <= xSheet.getLastRowNum(); rowNum++) {
                    XSSFRow xRow = xSheet.getRow(rowNum);
                    if (xRow == null) {
                        continue;
                    }

                    // 循环列Cell
                    for (int cellNum = 0; cellNum <= xRow.getLastCellNum(); cellNum++) {
                        XSSFCell xCell = xRow.getCell(cellNum);
                        if (xCell == null) {
                            continue;
                        }
                        System.out.print("        " + getValue(xCell));
                    }
                    System.out.println();
                }
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private String getValue(XSSFCell xCell) {
        if (xCell.getCellType() == XSSFCell.CELL_TYPE_BOOLEAN) {

            return String.valueOf(xCell.getBooleanCellValue());
        } else if (xCell.getCellType() == XSSFCell.CELL_TYPE_NUMERIC) {

            return String.valueOf(xCell.getNumericCellValue());
        } else {

            return String.valueOf(xCell.getStringCellValue());
        }

    }

    public static void main(String[] args) {
        ReadExcelPOI readExcelService = new ReadExcelPOI();
        readExcelService.readExcel();
    }
}

修改：

public class WriteExcelPOI {

    public void writeExcelPOI() {
        try {

            String fileName = "E:\\xxx\\xxx\\a.xlsx";
            XSSFWorkbook xwb = new XSSFWorkbook(new FileInputStream(fileName));

            XSSFSheet xSheet = xwb.getSheetAt(0);
            XSSFRow xRow = xSheet.createRow(0);
            XSSFCell xCell = xRow.createCell(0);

            xCell.setCellValue("asdfasd");

            FileOutputStream out = new FileOutputStream(fileName);
            xwb.write(out);
            out.close();

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private String getValue(XSSFCell xCell) {
        if (xCell.getCellType() == XSSFCell.CELL_TYPE_BOOLEAN) {

            return String.valueOf(xCell.getBooleanCellValue());
        } else if (xCell.getCellType() == XSSFCell.CELL_TYPE_NUMERIC) {

            return String.valueOf(xCell.getNumericCellValue());
        } else {

            return String.valueOf(xCell.getStringCellValue());
        }

    }

    public static void main(String[] args) {
        WriteExcelPOI a = new WriteExcelPOI();
        a.writeExcelPOI();
    }
}

读的时候下面都可以：
方法一：
String fileName = "E:\\xxx\\xxx\\a.xlsx";
XSSFWorkbook xwb = new XSSFWorkbook(fileName);
方法二：
String fileName = "E:\\xxx\\xxx\\a.xlsx";
XSSFWorkbook xwb = new XSSFWorkbook(new FileInputStream(fileName));

修改的时候，只能使用流：
String fileName = "E:\\xxx\\xxx\\a.xlsx";
XSSFWorkbook xwb = new XSSFWorkbook(new FileInputStream(fileName));


区别就是在为何 使用流就可以修改成功，而去的时候直接使用文件名称也是可以的。

开始的时候我就是使用了文件名称修改，就是不行。贴出来给遇到的同学也有个参考。