Java poi 的通用工具类

以下是一个基于 Apache POI 的通用工具类，可以用于读取和写入 Excel 文件。

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
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 文件中的数据
     * 
     * @param filePath 文件路径
     * @return 读取到的数据列表
     * @throws IOException
     */
    public static List<List<String>> readExcel(String filePath) throws IOException {
        List<List<String>> result = new ArrayList<>();
        FileInputStream inputStream = new FileInputStream(new File(filePath));
        Workbook workbook = new XSSFWorkbook(inputStream);
        Sheet sheet = workbook.getSheetAt(0);
        Iterator<Row> rowIterator = sheet.iterator();

        while (rowIterator.hasNext()) {
            Row row = rowIterator.next();
            Iterator<Cell> cellIterator = row.iterator();
            List<String> rowData = new ArrayList<>();
            while (cellIterator.hasNext()) {
                Cell cell = cellIterator.next();
                switch (cell.getCellType()) {
                    case STRING:
                        rowData.add(cell.getStringCellValue());
                        break;
                    case BOOLEAN:
                        rowData.add(String.valueOf(cell.getBooleanCellValue()));
                        break;
                    case NUMERIC:
                        rowData.add(String.valueOf(cell.getNumericCellValue()));
                        break;
                    default:
                        rowData.add("");
                }
            }
            result.add(rowData);
        }
        workbook.close();
        inputStream.close();
        return result;
    }

    /**
     * 将数据写入 Excel 文件
     * 
     * @param filePath 文件路径
     * @param data     要写入的数据
     * @throws IOException
     */
    public static void writeExcel(String filePath, List<List<String>> data) throws IOException {
        Workbook workbook = new XSSFWorkbook();
        Sheet sheet = workbook.createSheet();

        int rownum = 0;
        for (List<String> rowData : data) {
            Row row = sheet.createRow(rownum++);
            int cellnum = 0;
            for (String cellData : rowData) {
                Cell cell = row.createCell(cellnum++);
                cell.setCellValue(cellData);
            }
        }

        FileOutputStream outputStream = new FileOutputStream(filePath);
        workbook.write(outputStream);
        workbook.close();
        outputStream.close();
    }
}

这个工具类包含了两个方法，`readExcel()` 方法用于读取 Excel 文件中的数据，`writeExcel()` 方法用于将数据写入到 Excel 文件中。使用时只需传入文件路径和数据即可。