Java 讀取 Excel 文件全攻略：Apache POI 入門、實作與常見問題解析

<dependency>
  <groupId>org.apache.poi</groupId>
  <artifactId>poi-ooxml</artifactId>
  <version>5.2.3</version>
</dependency>

implementation 'org.apache.poi:poi-ooxml:5.2.3'

import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;

import java.io.*;

public class ExcelReader {
    public static void main(String[] args) {
        String filePath = "data.xlsx"; // 可改為 data.xls
        try (InputStream inp = new FileInputStream(filePath);
             Workbook workbook = createWorkbook(inp, filePath)) {

            for (int i = 0; i < workbook.getNumberOfSheets(); i++) {
                Sheet sheet = workbook.getSheetAt(i);
                System.out.println("Sheet: " + sheet.getSheetName());
                for (Row row : sheet) {
                    for (Cell cell : row) {
                        System.out.print(getCellValue(cell) + "\t");
                    }
                    System.out.println();
                }
            }
        } catch (IOException e) {
            System.err.println("讀取 Excel 發生錯誤：" + e.getMessage());
        }
    }

    // 根據副檔名自動選擇 Workbook 類型
    private static Workbook createWorkbook(InputStream inp, String filePath) throws IOException {
        if (filePath.endsWith(".xlsx")) {
            return new XSSFWorkbook(inp);
        } else if (filePath.endsWith(".xls")) {
            return new HSSFWorkbook(inp);
        } else {
            throw new IllegalArgumentException("不支援的檔案格式：" + filePath);
        }
    }

    // 取得儲存格內容，型別判斷見下節
    private static String getCellValue(Cell cell) {
        switch (cell.getCellType()) {
            case STRING: return cell.getStringCellValue();
            case NUMERIC:
                if (DateUtil.isCellDateFormatted(cell)) {
                    return cell.getDateCellValue().toString();
                } else {
                    return String.valueOf(cell.getNumericCellValue());
                }
            case BOOLEAN: return String.valueOf(cell.getBooleanCellValue());
            case FORMULA: return cell.getCellFormula();
            case BLANK: return "";
            default: return "未知型別";
        }
    }
}

Sheet sheet = workbook.getSheet("任務清單");
if (sheet != null) {
    // 處理該 Sheet 資料
}