苍穹外卖V2

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// 代码示例
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public static void write() throws Exception {
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    // 1. 创建工作簿、工作表
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    XSSFWorkbook excel = new XSSFWorkbook();
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    XSSFSheet sheet = excel.createSheet("info");
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    // 2. 表头行（第1行，下标1）
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    XSSFRow row1 = sheet.createRow(1);
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    row1.createCell(1).setCellValue("姓名");
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    row1.createCell(2).setCellValue("城市");
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    // 3. 数据行
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    XSSFRow row2 = sheet.createRow(2);
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    row2.createCell(1).setCellValue("张三");
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    row2.createCell(2).setCellValue("北京");
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    XSSFRow row3 = sheet.createRow(3);
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    row3.createCell(1).setCellValue("李四");
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    row3.createCell(2).setCellValue("南京");
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    // 4. 输出到文件
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    FileOutputStream out = new FileOutputStream(new File("D:\\info.xlsx"));
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    excel.write(out); // 原代码缺失此行，必报错！
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    out.close();
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    excel.close();
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}

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public static void read() throws Exception {
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    // 1. 读取文件流、工作簿、工作表
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    FileInputStream in = new FileInputStream(new File("D:\\info.xlsx"));
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    XSSFWorkbook excel = new XSSFWorkbook(in);
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    XSSFSheet sheet = excel.getSheetAt(0);
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    // 2. 遍历所有行
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    int lastRow = sheet.getLastRowNum();
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    for (int i = 1; i <= lastRow; i++) {
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        XSSFRow row = sheet.getRow(i);
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        String name = row.getCell(1).getStringCellValue();
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        String city = row.getCell(2).getStringCellValue();
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        System.out.println(name + " " + city);
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    }
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    // 3. 关闭资源
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    in.close();
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    excel.close();
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}

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// ========== 拓展1：Sheet工作表高频操作 ==========
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 public static void sheetOperateDemo(XSSFWorkbook excel) {
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     // 根据表名获取sheet
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     XSSFSheet sheet = excel.getSheet("info");
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     // 获取真实有数据总行数
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     int realRowCount = sheet.getPhysicalNumberOfRows();
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     // 设置固定列宽 / 自动适配列宽
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     sheet.setColumnWidth(1, 15 * 256);
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     sheet.autoSizeColumn(2);
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     // 删除指定行
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     XSSFRow delRow = sheet.getRow(2);
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     sheet.removeRow(delRow);
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 }
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 // ========== 拓展2：Row行高频操作 ==========
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 public static void rowOperateDemo(XSSFSheet sheet) {
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     XSSFRow row = sheet.getRow(2);
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     // 获取当前行最后一列下标
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     int lastCellIndex = row.getLastCellNum();
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     // 获取当前行有效单元格数量
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     int realCellCount = row.getPhysicalNumberOfCells();
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     // 动态遍历本行所有单元格
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     for (int c = 0; c < lastCellIndex; c++) {
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         XSSFCell cell = row.getCell(c);
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     }
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 }
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 // ========== 拓展3：Cell单元格通用工具（解决类型转换报错） ==========
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 public static String getCellValue(XSSFCell cell) {
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     if (cell == null) return "";
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     return switch (cell.getCellType()) {
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         case STRING -> cell.getStringCellValue();
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         case NUMERIC -> String.valueOf(cell.getNumericCellValue());
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         case BOOLEAN -> String.valueOf(cell.getBooleanCellValue());
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         case FORMULA -> cell.getCellFormula();
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         default -> "";
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     };
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 }
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 // 单元格写入数字/布尔/公式示例
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 public static void cellWriteDemo(XSSFRow row) {
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     XSSFCell cell = row.createCell(3);
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     cell.setCellValue(99.9);
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     cell.setCellValue(true);
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     cell.setCellFormula("SUM(B2:B10)");
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 }
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 // ========== 拓展4：单元格样式、字体设置 ==========
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 public static void cellStyleDemo(XSSFWorkbook excel, XSSFRow row) {
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     // 创建字体
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     XSSFFont font = excel.createFont();
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     font.setBold(true);
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     font.setFontHeightInPoints(12);
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     font.setColor(IndexedColors.RED.getIndex());
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     // 创建样式
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     XSSFCellStyle style = excel.createCellStyle();
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     style.setFont(font);
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     style.setAlignment(HorizontalAlignment.CENTER);
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     style.setVerticalAlignment(VerticalAlignment.CENTER);
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     // 绑定样式到单元格
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     XSSFCell cell = row.createCell(1);
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     cell.setCellValue("带样式表头");
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     cell.setCellStyle(style);
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 }
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 // ========== 拓展5：try-with-resources 自动关闭流（无手动close） ==========
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 public static void autoCloseResourceDemo() throws Exception {
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     try (FileOutputStream out = new FileOutputStream("D:\\info.xlsx");
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          XSSFWorkbook excel = new XSSFWorkbook()) {
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         XSSFSheet sheet = excel.createSheet("info");
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         sheet.createRow(0).createCell(0).setCellValue("测试自动关闭流");
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         excel.write(out);
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     }
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 }