写一个ExcelUtils类

好的，我理解你的要求了。ExcelUtils类是一个用于操作Excel文件的工具类。下面是一个简单的实现：

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.util.ArrayList;
import java.util.List;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class ExcelUtils {

    // 读取Excel文件
    public static List<List<String>> readExcel(String filePath) {
        List<List<String>> dataList = new ArrayList<>();
        try {
            File file = new File(filePath);
            FileInputStream inputStream = new FileInputStream(file);
            Workbook workbook = new XSSFWorkbook(inputStream);
            Sheet sheet = workbook.getSheetAt(0);
            for (int i = 0; i <= sheet.getLastRowNum(); i++) {
                Row row = sheet.getRow(i);
                List<String> rowList = new ArrayList<>();
                for (int j = 0; j < row.getLastCellNum(); j++) {
                    Cell cell = row.getCell(j);
                    String cellValue = "";
                    if (cell != null) {
                        switch (cell.getCellType()) {
                        case STRING:
                            cellValue = cell.getStringCellValue();
                            break;
                        case NUMERIC:
                            cellValue = String.valueOf(cell.getNumericCellValue());
                            break;
                        case BOOLEAN:
                            cellValue = String.valueOf(cell.getBooleanCellValue());
                            break;
                        case FORMULA:
                            cellValue = cell.getCellFormula();
                            break;
                        default:
                            cellValue = "";
                            break;
                        }
                    }
                    rowList.add(cellValue);
                }
                dataList.add(rowList);
            }
            inputStream.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return dataList;
    }

    // 写入Excel文件
    public static void writeExcel(String filePath, List<List<String>> dataList) {
        try {
            Workbook workbook = new XSSFWorkbook();
            Sheet sheet = workbook.createSheet();
            for (int i = 0; i < dataList.size(); i++) {
                List<String> rowList = dataList.get(i);
                Row row = sheet.createRow(i);
                for (int j = 0; j < rowList.size(); j++) {
                    Cell cell = row.createCell(j);
                    cell.setCellValue(rowList.get(j));
                }
            }
            FileOutputStream outputStream = new FileOutputStream(filePath);
            workbook.write(outputStream);
            outputStream.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

这个ExcelUtils类提供两个方法：readExcel和writeExcel，分别用于读取和写入Excel文件。你可以调用这些方法来读取和写入Excel文件，也可以按照你的需求对这个类进行扩展和优化。

希望这个回答能够满足你的需求。如果有任何问题，请随时提出。