POI，Excel读写，兼容.xls、.xlsx

// POI 
        
    // 兼容.xls、.xlsx   参数:  路径 sheet 列 行　　

    public static String readExcel(String path, String st, int i, int j) throws IOException {        
        File file = new File(path);
        String FileName = file.getName();
        String FileType = FileName.substring(FileName.lastIndexOf("."));        
        if (FileType.equals(".xlsx")) {            
            InputStream is = new FileInputStream(path);            
            XSSFWorkbook xssfWorkbook = new XSSFWorkbook(is);
            XSSFSheet hssfSheet = xssfWorkbook.getSheet(st);
            XSSFRow hssfRow = hssfSheet.getRow(j);
            if (hssfRow != null) {
                String cell = hssfRow.getCell(i).toString();
                return cell;
            }
            return null;            
        } else if (FileType.equals(".xls")) {
            InputStream is = new FileInputStream(path);
            HSSFWorkbook hssfWorkbook = new HSSFWorkbook(is);
            HSSFSheet hssfSheet = hssfWorkbook.getSheet(st);
            HSSFRow hssfRow = hssfSheet.getRow(j);
            if (hssfRow != null) {
                String cell = hssfRow.getCell(i).toString();
                return cell;
            }
            return null;
        }
        return null;
    }
    
    // 兼容.xls、.xlsx 写 追加   
　　//参数： 路径 sheet  列  行  插入字符串

    public static void writeExcel(String path, String st, int i, int j, String str)
            throws FileNotFoundException, IOException {
        File file = new File(path);
        String FileName = file.getName();
        String FileType = FileName.substring(FileName.lastIndexOf("."));
        if (FileType.equals(".xlsx")) {
            InputStream is = new FileInputStream(path);
            XSSFWorkbook xwb = new XSSFWorkbook(is);
            XSSFSheet sheet = xwb.getSheet(st);    
            if(sheet!=null) {
                XSSFRow row ;
                if(sheet.getRow(j)!=null) {
                     row = sheet.getRow(j);
                }else {
                    row = sheet.createRow(j);
                }
                XSSFCell cell = row.createCell(i);
                cell.setCellValue(str);            
                xwb.write(new FileOutputStream(path));
            }
        } else if (FileType.equals(".xls")) {
            InputStream is = new FileInputStream(path);
            HSSFWorkbook hwb = new HSSFWorkbook(is);
            HSSFSheet sheet = hwb.getSheet(st);
            if(sheet!=null) {
                HSSFRow row ;
                if(sheet.getRow(j)!=null) {
                     row = sheet.getRow(j);
                }else {
                    row = sheet.createRow(j);
                }
                HSSFCell cell = row.createCell(i);
                cell.setCellValue(str);                
                hwb.write(new FileOutputStream(path));
            }
        }
    }