java生成excel文件到指定目录，使用hutool

使用Hutool生成Excel文件到指定目录的代码如下：

import cn.hutool.poi.excel.ExcelUtil;
import cn.hutool.poi.excel.ExcelWriter;
import cn.hutool.poi.excel.cell.CellStyleBuilder;
import cn.hutool.poi.excel.cell.CellUtil;
import cn.hutool.poi.excel.style.Align;

import java.util.List;

public class ExcelUtilDemo {
    
    public static void main(String[] args) {
        List<User> userList = getUserList();
        
        // 创建Excel写入器
        ExcelWriter writer = ExcelUtil.getWriter("D:\\test.xlsx");
        
        // 自定义标题样式
        CellStyleBuilder titleStyleBuilder = writer.getCellStyleBuilder();
        titleStyleBuilder.bgColor(Color.LIGHT_GRAY);
        titleStyleBuilder.align(Align.CENTER);
        titleStyleBuilder.borderBottom(BorderStyle.THIN);
        CellStyle titleStyle = titleStyleBuilder.build();
        
        // 写入标题行
        writer.merge(3, "用户列表"); // 合并单元格
        CellUtil.createCell(writer.getRow(0), 0, "姓名", titleStyle);
        CellUtil.createCell(writer.getRow(0), 1, "年龄", titleStyle);
        CellUtil.createCell(writer.getRow(0), 2, "性别", titleStyle);
        CellUtil.createCell(writer.getRow(0), 3, "地址", titleStyle);
        
        // 写入数据行
        for (int i = 0; i < userList.size(); i++) {
            User user = userList.get(i);
            CellUtil.createCell(writer.getRow(i + 1), 0, user.getName());
            CellUtil.createCell(writer.getRow(i + 1), 1, user.getAge());
            CellUtil.createCell(writer.getRow(i + 1), 2, user.getGender());
            CellUtil.createCell(writer.getRow(i + 1), 3, user.getAddress());
        }
        
        // 关闭Excel写入器
        writer.close();
    }
    
    private static List<User> getUserList() {
        // TODO: 返回用户列表
        return null;
    }
    
    private static class User {
        private String name;
        private int age;
        private String gender;
        private String address;
        
        public User(String name, int age, String gender, String address) {
            this.name = name;
            this.age = age;
            this.gender = gender;
            this.address = address;
        }
        
        public String getName() {
            return name;
        }
        
        public void setName(String name) {
            this.name = name;
        }
        
        public int getAge() {
            return age;
        }
        
        public void setAge(int age) {
            this.age = age;
        }
        
        public String getGender() {
            return gender;
        }
        
        public void setGender(String gender) {
            this.gender = gender;
        }
        
        public String getAddress() {
            return address;
        }
        
        public void setAddress(String address) {
            this.address = address;
        }
    }
}

上面的代码中，我们使用`ExcelWriter`类来创建Excel文件，并将其保存到指定目录。通过`CellStyleBuilder`类可以自定义单元格样式，例如设置背景颜色、对齐方式、边框等。`CellUtil`类可以操作单元格，例如合并单元格、创建单元格等。最后，通过`ExcelWriter`的`close`方法关闭文件流。