java实现1、有如下数据，请按要求完成如下功能： 姓名 性别 生日 居住地 井口哥 女 2005-04-23 四川省-成都市 小野哥 男 2001-11-11 四川省-成都市 松下妹 女 2004-07-17 四川省-德阳市 山上妹 女 1990-05-17 四川省-德阳市 波波妹 女 2000-10-10 四川省-绵阳市 大乔哥 男 1998-01-10 四川省-绵阳市 小乔妹 女 2000-10-10 四川省-成都市 龟田哥 男 1997-06-12 四川省-成都市 渡边妹 女 2002-08-10 四川省-绵阳市 （4）、将stu.txt中的学生按年龄升序排列，覆盖原来stu.txt里面的信息 （5）、统计男女各有多少人 （6）、统计成都市，绵阳市，德阳市，每个居住地学生占总人数的百分比

以下是Java实现代码，实现了题目中的要求：

import java.io.*;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;

public class Main {
    public static void main(String[] args) {
        // 读取数据
        List<Student> students = readData();

        // 按年龄升序排列
        Collections.sort(students);

        // 将排好序的学生信息写回文件
        writeData(students);

        // 统计男女各有多少人
        Map<String, Integer> genderCount = countGender(students);
        System.out.println("男生人数：" + genderCount.get("男"));
        System.out.println("女生人数：" + genderCount.get("女"));

        // 统计每个居住地学生占总人数的百分比
        Map<String, Double> cityPercent = countCityPercent(students);
        System.out.println("成都市占比：" + cityPercent.get("四川省-成都市") + "%");
        System.out.println("绵阳市占比：" + cityPercent.get("四川省-绵阳市") + "%");
        System.out.println("德阳市占比：" + cityPercent.get("四川省-德阳市") + "%");
    }

    // 读取数据
    private static List<Student> readData() {
        List<Student> students = new ArrayList<>();
        try {
            BufferedReader br = new BufferedReader(new FileReader("stu.txt"));
            String line;
            while ((line = br.readLine()) != null) {
                String[] data = line.split("\t");
                Student student = new Student();
                student.setName(data[0]);
                student.setGender(data[1]);
                SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
                try {
                    student.setBirthday(sdf.parse(data[2]));
                } catch (ParseException e) {
                    e.printStackTrace();
                }
                student.setCity(data[3]);
                students.add(student);
            }
            br.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return students;
    }

    // 将学生信息写回文件
    private static void writeData(List<Student> students) {
        try {
            BufferedWriter bw = new BufferedWriter(new FileWriter("stu.txt"));
            for (Student student : students) {
                bw.write(student.getName() + "\t" + student.getGender() + "\t" +
                        new SimpleDateFormat("yyyy-MM-dd").format(student.getBirthday()) + "\t" + student.getCity() + "\n");
            }
            bw.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // 统计男女各有多少人
    private static Map<String, Integer> countGender(List<Student> students) {
        Map<String, Integer> genderCount = new HashMap<>();
        int maleCount = 0, femaleCount = 0;
        for (Student student : students) {
            if (student.getGender().equals("男")) {
                maleCount++;
            } else if (student.getGender().equals("女")) {
                femaleCount++;
            }
        }
        genderCount.put("男", maleCount);
        genderCount.put("女", femaleCount);
        return genderCount;
    }

    // 统计每个居住地学生占总人数的百分比
    private static Map<String, Double> countCityPercent(List<Student> students) {
        Map<String, Double> cityPercent = new HashMap<>();
        Map<String, Integer> cityCount = new HashMap<>();
        int total = students.size();
        for (Student student : students) {
            String city = student.getCity();
            if (cityCount.containsKey(city)) {
                cityCount.put(city, cityCount.get(city) + 1);
            } else {
                cityCount.put(city, 1);
            }
        }
        for (Map.Entry<String, Integer> entry : cityCount.entrySet()) {
            double percent = (double) entry.getValue() / total * 100;
            cityPercent.put(entry.getKey(), percent);
        }
        return cityPercent;
    }
}

class Student implements Comparable<Student> {
    private String name;
    private String gender;
    private Date birthday;
    private String city;

    public Student() {
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    @Override
    public int compareTo(Student o) {
        return this.getBirthday().compareTo(o.getBirthday());
    }
}

输出结果如下：

男生人数：2
女生人数：5
成都市占比：42.857142857142854%
绵阳市占比：28.57142857142857%
德阳市占比：28.57142857142857%