public class DemoUtils {
  public static Workbook readExcel(String filePath) {
    Workbook wb = null;
    if (filePath == null) {
      return null;
    }
    String extString = filePath.substring(filePath.lastIndexOf("."));
    InputStream is = null;
    try {
      is = new FileInputStream(filePath);
      if (".xls".equals(extString)) {
        return wb = new HSSFWorkbook(is);
      } else if (".xlsx".equals(extString)) {
        return wb = new XSSFWorkbook(is);
      } else {
        return wb = null;
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
    return wb;
  }
}

public class XXl {
  public static List<String> getString() {
    List<String> result = new ArrayList<String>();
    Workbook book = DemoUtils.readExcel("C:\\Users\\Administrator\\Desktop\\1.xlsx");
    int numberOfSheets = book.getNumberOfSheets();
    for (int number = 0; number < numberOfSheets; number++) {
      Sheet sheet = book.getSheetAt(number);
      System.out.println(sheet.getSheetName()); // 输出该表格的名称
      // 遍历所有行
      for (int rowNum = 1; rowNum <= sheet.getLastRowNum(); rowNum++) {
        Row row = sheet.getRow(rowNum);
        if (row == null) {
          continue;
        }
        int col = row.getPhysicalNumberOfCells();
        for (int j = 0; j < col; j++) {
          Cell cell = row.getCell(j);
          //判断该单元格是字符串还是数字类型
          String cellType = cell.getCellType().toString();
          if ("STRING".equals(cellType)) {
            System.out.println("第" + (rowNum + 1) + "行，第" + (j + 1) + "列的值是：》》》"
                + cell.getRichStringCellValue().getString());
            result.add(cell.getRichStringCellValue().getString());
          } else if ("NUMERIC".equals(cellType)) {
            NumberFormat ddf1=NumberFormat.getNumberInstance();  
            ddf1.setMaximumFractionDigits(0); 
            System.out.println(
                "第" + (rowNum + 1) + "行，第" + (j + 1) + "列的值是：》》》" + ddf1.format(cell.getNumericCellValue()));
            result.add(String.valueOf(ddf1.format(cell.getNumericCellValue())));
          }
        }
      }
    }
    return result;
  }
  public static void main(String[] args) {
    List<String> string = getString();
    for (String s : string) {
      System.out.print(s);
    }
  }
}

<dependencies>
    <!-- https://mvnrepository.com/artifact/org.apache.poi/poi -->
    <dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi</artifactId>
        <version>4.1.1</version>
    </dependency> 
    <!-- https://mvnrepository.com/artifact/org.apache.poi/poi-ooxml -->
    <dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi-ooxml</artifactId>
        <version>4.1.1</version>
    </dependency>       
  </dependencies>