我复制并粘贴了baeldung教程中的代码。

package aaanalysis;

    import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileNotFoundException;
    import java.io.FileOutputStream;
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;

    import org.apache.poi.ss.usermodel.Sheet;
    import org.apache.poi.ss.usermodel.Cell;
    import org.apache.poi.ss.usermodel.CellStyle;
    import org.apache.poi.ss.usermodel.DateUtil;
    import org.apache.poi.ss.usermodel.FillPatternType;
    import org.apache.poi.ss.usermodel.IndexedColors;
    import org.apache.poi.ss.usermodel.Row;
    import org.apache.poi.ss.usermodel.Workbook;
    import org.apache.poi.xssf.usermodel.XSSFFont;
    import org.apache.poi.xssf.usermodel.XSSFWorkbook;

    public class ExcelPOIHelper {

        public Map<Integer, List<String>> readExcel(String fileLocation) throws IOException {

            FileInputStream file = new FileInputStream(new File(fileLocation));
            Workbook workbook = new XSSFWorkbook(file);
            Sheet sheet = workbook.getSheetAt(0);

            Map<Integer, List<String>> data = new HashMap<>();
            int i = 0;
            for (Row row : sheet) {
                data.put(i, new ArrayList<String>());
                for (Cell cell : row) {
                    switch (cell.getCellTypeEnum()) {
                        case STRING: 
                            data.get(new Integer(i)).add(cell.getRichStringCellValue().getString());
                        case NUMERIC:  
//This is where the error is    if (DateUtil.isCellDateFormatted(cell)) {
                            data.get(i).add(cell.getDateCellValue() + "");
                        } else {
                            data.get(i).add(cell.getNumericCellValue() + "");
                        };
                        case BOOLEAN:  
                            data.get(i).add(cell.getBooleanCellValue() + "");
                        case FORMULA:  
                            data.get(i).add(cell.getCellFormula() + "");
                        default: data.get(new Integer(i)).add(" ");
                    }
                }
                i++;
            }
            return data;
        }
        public void writeExcel() throws IOException {
            //create workbook
            Workbook workbook = new XSSFWorkbook();

            //create sheet and set column widths
            Sheet sheet = workbook.createSheet("Persons");
            sheet.setColumnWidth(0, 6000);
            sheet.setColumnWidth(1, 4000);

            //create header row
            Row header = sheet.createRow(0);

            //Create style for the header
            CellStyle headerStyle = workbook.createCellStyle();
            headerStyle.setFillForegroundColor(IndexedColors.LIGHT_BLUE.getIndex());
            headerStyle.setFillPattern(FillPatternType.SOLID_FOREGROUND);

            //Set the font for the headerStyle
            XSSFFont font = ((XSSFWorkbook) workbook).createFont();
            font.setFontName("Arial");
            font.setFontHeightInPoints((short) 16);
            font.setBold(true);
            headerStyle.setFont(font);

            //Adding data to the sheet
            Cell headerCell = header.createCell(0);
            headerCell.setCellValue("Name");
            headerCell.setCellStyle(headerStyle);

            headerCell = header.createCell(1);
            headerCell.setCellValue("Age");
            headerCell.setCellStyle(headerStyle);

            CellStyle style = workbook.createCellStyle();
            style.setWrapText(true);

            Row row = sheet.createRow(2);
            Cell cell = row.createCell(0);
            cell.setCellValue("John Smith");
            cell.setCellStyle(style);

            cell = row.createCell(1);
            cell.setCellValue(20);
            cell.setCellStyle(style);

            File currDir = new File(".");
            String path = currDir.getAbsolutePath();
            String fileLocation = path.substring(0, path.length() - 1) + "temp.xlsx";

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

这是单元测试

import static org.junit.Assert.assertEquals;

import java.io.File;
import java.io.IOException;
import java.util.List;
import java.util.Map;

import org.junit.Before;
import org.junit.Test;

import aaanalysis.ExcelPOIHelper;

public class ExcelTest {
    private ExcelPOIHelper excelPOIHelper;
    private static String FILE_NAME = "temp.xlsx";
    private String fileLocation;

    @Before
    public void generateExcelFile() throws IOException {
        File currDir = new File(".");
        String path = currDir.getAbsolutePath();
        fileLocation = path.substring(0, path.length() - 1) + FILE_NAME;

        excelPOIHelper = new ExcelPOIHelper();
        excelPOIHelper.writeExcel();
    }

    @Test
    public void whenParsingPOIExcelFile_thenCorrect() throws IOException {
        Map<Integer, List<String>> data = excelPOIHelper.readExcel(fileLocation);

        assertEquals("Name", data.get(0).get(0));
        assertEquals("Age", data.get(0).get(1));

        assertEquals("John Smith", data.get(1).get(0));
        assertEquals("20", data.get(1).get(1));
    }
}

另外要注意的是，当添加到工作表时，标题后面的行被跳过并直接转到第二行，尽管Assert似乎不匹配。这里的问题是什么。其他答案似乎不能解决问题。