编写一个程序，实现一下功能，要求 设计一个学生student类，包含学号、姓名、出生日期、性别等字段 从input.txt(从附件下载)中读取其中的学生信息，并存入学生集合list中 对学生集合list进行排序，按照出生日期从早到晚排序（即年龄由大到小） 将排序后的学生集合list输出到output.txt文件中，输出格式同input.txt：一行一个学生，依次输出学号、姓名、出生日期、性别并用空格隔开 Java代码

以下是Java代码实现：

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Date;
import java.util.List;
import java.util.Scanner;

public class StudentSorter {
    public static void main(String[] args) {
        List<Student> studentList = new ArrayList<>();
        try {
            File inputFile = new File("input.txt");
            Scanner scanner = new Scanner(inputFile);
            while (scanner.hasNextLine()) {
                String line = scanner.nextLine();
                String[] fields = line.split("\\s+");
                Student student = new Student(fields[0], fields[1], fields[2], fields[3]);
                studentList.add(student);
            }
            scanner.close();
        } catch (IOException e) {
            e.printStackTrace();
        }

        Collections.sort(studentList, new Comparator<Student>() {
            @Override
            public int compare(Student s1, Student s2) {
                SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
                try {
                    Date d1 = sdf.parse(s1.getBirthday());
                    Date d2 = sdf.parse(s2.getBirthday());
                    return d1.compareTo(d2);
                } catch (ParseException e) {
                    e.printStackTrace();
                    return 0;
                }
            }
        });

        try {
            File outputFile = new File("output.txt");
            FileWriter writer = new FileWriter(outputFile);
            for (Student student : studentList) {
                writer.write(student.getNumber() + " " + student.getName() + " " +
                        student.getBirthday() + " " + student.getGender() + "\n");
            }
            writer.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

class Student {
    private String number;
    private String name;
    private String birthday;
    private String gender;

    public Student(String number, String name, String birthday, String gender) {
        this.number = number;
        this.name = name;
        this.birthday = birthday;
        this.gender = gender;
    }

    public String getNumber() {
        return number;
    }

    public String getName() {
        return name;
    }

    public String getBirthday() {
        return birthday;
    }

    public String getGender() {
        return gender;
    }
}

程序读取input.txt文件中的学生信息，并将其存储在一个List<Student>对象中。然后，使用Collections.sort()方法对该List进行排序，排序的规则是按照学生的出生日期从早到晚排序。最后，程序将排序后的学生信息写入output.txt文件中。