JAVA语言POI导出EXCEL设置首行标题合并单元格再加上标题居中, 加粗,并且所有单元格加上边框,请给出完整示例

好的，以下是一个完整的示例代码，实现了首行标题合并单元格、标题居中、加粗和单元格边框的要求：

import java.io.FileOutputStream;
import java.io.IOException;
import org.apache.poi.ss.usermodel.BorderStyle;
import org.apache.poi.ss.usermodel.CellStyle;
import org.apache.poi.ss.usermodel.Font;
import org.apache.poi.ss.usermodel.HorizontalAlignment;
import org.apache.poi.ss.usermodel.IndexedColors;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.VerticalAlignment;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class ExcelExportExample {
    public static void main(String[] args) {
        // 创建工作簿和活动表
        XSSFWorkbook workbook = new XSSFWorkbook();
        Sheet sheet = workbook.createSheet("学生成绩单");

        // 设置标题
        Row titleRow = sheet.createRow(0);
        titleRow.createCell(0).setCellValue("学生成绩单");
        sheet.addMergedRegion(CellRangeAddress.valueOf("A1:C1"));
        CellStyle titleStyle = workbook.createCellStyle();
        titleStyle.setAlignment(HorizontalAlignment.CENTER);
        Font titleFont = workbook.createFont();
        titleFont.setBold(true);
        titleStyle.setFont(titleFont);
        titleRow.getCell(0).setCellStyle(titleStyle);

        // 设置表头
        Row headerRow = sheet.createRow(1);
        headerRow.createCell(0).setCellValue("姓名");
        headerRow.createCell(1).setCellValue("语文");
        headerRow.createCell(2).setCellValue("数学");
        CellStyle headerStyle = workbook.createCellStyle();
        headerStyle.setAlignment(HorizontalAlignment.CENTER);
        headerStyle.setVerticalAlignment(VerticalAlignment.CENTER);
        headerStyle.setBorderTop(BorderStyle.THIN);
        headerStyle.setBorderRight(BorderStyle.THIN);
        headerStyle.setBorderBottom(BorderStyle.THIN);
        headerStyle.setBorderLeft(BorderStyle.THIN);
        headerStyle.setFillForegroundColor(IndexedColors.GREY_25_PERCENT.getIndex());
        headerStyle.setFillPattern(FillPatternType.SOLID_FOREGROUND);
        Font headerFont = workbook.createFont();
        headerFont.setBold(true);
        headerStyle.setFont(headerFont);
        for (int i = 0; i < headerRow.getLastCellNum(); i++) {
            headerRow.getCell(i).setCellStyle(headerStyle);
        }

        // 设置学生成绩
        Row dataRow1 = sheet.createRow(2);
        dataRow1.createCell(0).setCellValue("张三");
        dataRow1.createCell(1).setCellValue(90);
        dataRow1.createCell(2).setCellValue(80);

        Row dataRow2 = sheet.createRow(3);
        dataRow2.createCell(0).setCellValue("李四");
        dataRow2.createCell(1).setCellValue(85);
        dataRow2.createCell(2).setCellValue(92);

        Row dataRow3 = sheet.createRow(4);
        dataRow3.createCell(0).setCellValue("王五");
        dataRow3.createCell(1).setCellValue(88);
        dataRow3.createCell(2).setCellValue(87);

        // 设置单元格边框
        CellStyle dataStyle = workbook.createCellStyle();
        dataStyle.setAlignment(HorizontalAlignment.CENTER);
        dataStyle.setVerticalAlignment(VerticalAlignment.CENTER);
        dataStyle.setBorderTop(BorderStyle.THIN);
        dataStyle.setBorderRight(BorderStyle.THIN);
        dataStyle.setBorderBottom(BorderStyle.THIN);
        dataStyle.setBorderLeft(BorderStyle.THIN);
        for (int i = 2; i <= sheet.getLastRowNum(); i++) {
            Row row = sheet.getRow(i);
            for (int j = 0; j < row.getLastCellNum(); j++) {
                row.getCell(j).setCellStyle(dataStyle);
            }
        }

        // 保存文件
        try (FileOutputStream outputStream = new FileOutputStream("example.xlsx")) {
            workbook.write(outputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

在上面的代码中，我们首先创建工作簿和活动表，然后使用 `sheet.addMergedRegion()` 将 A1 到 C1 的单元格合并成一个单元格，并使用 `CellStyle` 和 `Font` 分别设置居中和加粗样式。接着，我们设置了表头和学生成绩，并使用循环为表头和学生成绩的单元格设置了边框和填充颜色样式。最后，我们使用 `workbook.write()` 将工作簿保存到本地。