XSSFWorkbook workbook = new XSSFWorkbook();
XSSFSheet sheet = workbook.createSheet("test");
FileOutputStream fileOutputStream = new FileOutputStream("test.xlsx");
workbook.write(fileOutputStream);
fileOutputStream.close();

XSSFWorkbook workbook = new XSSFWorkbook();
XSSFSheet sheet = workbook.createSheet("test");
XSSFRow row = sheet.createRow(3);
XSSFCell cell = row.createCell(0);
cell.setCellValue("Hello World");
FileOutputStream fileOutputStream = new FileOutputStream("test.xlsx");
workbook.write(fileOutputStream);
fileOutputStream.close();

// 创建单元格样式对象
XSSFCellStyle cellStyle = workbook.createCellStyle();

// 设置边框
// 设置下边框
cellStyle.setBorderBottom(BorderStyle.DASH_DOT);
// 设置上边框
cellStyle.setBorderBottom(BorderStyle.HAIR);

// 设置字体
// 创建字体对象
Font font = workbook.createFont();
// 设置字体
font.setFontName("仿宋");
// 设置字号
font.setFontHeightInPoints((short) 28);
cellStyle.setFont(font);

// 设置宽高
// 设置第一列的宽度是 31 个字符宽度
sheet.setColumnWidth(0,31*256);
// 设置行的高度是 50 个点
row.setHeightInPoints(50);

// 设置居中显示
// 水平居中
cellStyle.setAlignment(HorizontalAlignment.CENTER);
// 垂直居中
cellStyle.setVerticalAlignment(VerticalAlignment.CENTER);

// 设置单元格样式
cell.setCellStyle(cellStyle);

// 合并单元格
CellRangeAddress region = new CellRangeAddress(0, 3, 0, 3);
sheet.addMergedRegion(region);
fileOutputStream.close();

XSSFWorkbook workbook = new XSSFWorkbook();
XSSFSheet sheet = workbook.createSheet("test");
// 读取图片
FileInputStream fileInputStream = new FileInputStream("/Users/humingchao/IdeaProjects/SaaS_ihrm/poiTest/p1.jpg");
byte[] bytes = IOUtils.toByteArray(fileInputStream);
fileInputStream.read(bytes);

// 向 POI 内存添加一张图片，并返回该图片在 Excel 中的图片集合中的下标
int index = workbook.addPicture(bytes, Workbook.PICTURE_TYPE_JPEG);
// 绘制图片工具类
XSSFCreationHelper helper = workbook.getCreationHelper();
// 创建一个绘图对象
Drawing<?> patriarch = sheet.createDrawingPatriarch();
// 创建锚点，设置图片坐标
ClientAnchor anchor = helper.createClientAnchor();
// 行从 0 开始
anchor.setRow1(0);
// 列从 0 开始
anchor.setCol1(0);

// 创建图片
Picture picture = patriarch.createPicture(anchor, index);
picture.resize();

// 文件流
FileOutputStream fileOutputStream = new FileOutputStream("test3.xlsx");
// 写入文件
workbook.write(fileOutputStream);
fileOutputStream.close();

public static void main(String[] args) throws Exception {
   // 创建 workbook 工作簿
   XSSFWorkbook workbook = new XSSFWorkbook("demo.xlsx");
   // 获取 sheet 从 0 开始
   Sheet sheet = workbook.getSheetAt(0);

   int totalRowNum = sheet.getLastRowNum();

   Row row = null;
   Cell cell = null;

  // 循环所有行
   for (int rowNum = 0; rowNum <=sheet.getLastRowNum(); rowNum++) {
      row = sheet.getRow(rowNum);
      StringBuilder stringBuilder = new StringBuilder();
     // 循环每行中的所有单元格
      for (int cellNum = 2; cellNum < row.getLastCellNum(); cellNum++) {
         cell = row.getCell(cellNum);
         stringBuilder.append(getValue(cell)).append("-");
      }
      System.out.println(stringBuilder.toString());
   }
}

// 获取数据
public static Object getValue(Cell cell) {
   Object value = null;
   switch (cell.getCellType()) {
      case STRING:
         value = cell.getStringCellValue();
         break;
      case BOOLEAN:
         value = cell.getBooleanCellValue();
         break;
		// 数字类型（包含日期和普通数字）
     case NUMERIC:
         if (DateUtil.isCellDateFormatted(cell)) {
            value = cell.getDateCellValue();
         } else {
            value = cell.getNumericCellValue();
         }
         break;
		// 公式类型
     case FORMULA:
         value = cell.getCellFormula();
         break;
      default:
         break;
   }
   return value;
}