使用Java编写一个学生管理系统，需要包括添加，排序，查询，修改，删除学生信息的功能，学生的信息包括学号，年龄，性别，数学与语文与英语的成绩以及它的平均分

好的，这是一个比较复杂的问题。首先，你需要定义一个学生类，包括学号、年龄、性别、数学、语文、英语成绩以及平均分等属性。可以按照以下方式定义：

public class Student {
    private String id;
    private int age;
    private String gender;
    private double mathScore;
    private double chineseScore;
    private double englishScore;
    private double averageScore;
    // 构造函数
    public Student(String id, int age, String gender, double mathScore, double chineseScore, double englishScore, double averageScore) {
        this.id = id;
        this.age = age;
        this.gender = gender;
        this.mathScore = mathScore;
        this.chineseScore = chineseScore;
        this.englishScore = englishScore;
        this.averageScore = averageScore;
    }
    // getter、setter方法
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    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 double getMathScore() {
        return mathScore;
    }
    public void setMathScore(double mathScore) {
        this.mathScore = mathScore;
    }
    public double getChineseScore() {
        return chineseScore;
    }
    public void setChineseScore(double chineseScore) {
        this.chineseScore = chineseScore;
    }
    public double getEnglishScore() {
        return englishScore;
    }
    public void setEnglishScore(double englishScore) {
        this.englishScore = englishScore;
    }
    public double getAverageScore() {
        return averageScore;
    }
    public void setAverageScore(double averageScore) {
        this.averageScore = averageScore;
    }
}

接下来，你需要编写一个学生管理类，包含添加、排序、查询、修改和删除学生信息的方法。可以按照以下方式定义：

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.Scanner;

public class StudentManager {
    private List<Student> studentList = new ArrayList<Student>();
    // 添加学生信息
    public void addStudent() {
        Scanner input = new Scanner(System.in);
        System.out.println("请输入学生信息：");
        System.out.print("学号：");
        String id = input.next();
        System.out.print("年龄：");
        int age = input.nextInt();
        System.out.print("性别：");
        String gender = input.next();
        System.out.print("数学成绩：");
        double mathScore = input.nextDouble();
        System.out.print("语文成绩：");
        double chineseScore = input.nextDouble();
        System.out.print("英语成绩：");
        double englishScore = input.nextDouble();
        double averageScore = (mathScore + chineseScore + englishScore) / 3; // 计算平均分
        Student student = new Student(id, age, gender, mathScore, chineseScore, englishScore, averageScore);
        studentList.add(student);
        System.out.println("添加成功！");
    }
    // 排序
    public void sortStudent() {
        Collections.sort(studentList, new Comparator<Student>() {
            @Override
            public int compare(Student o1, Student o2) {
                if (o1.getAverageScore() > o2.getAverageScore()) {
                    return -1;
                } else if (o1.getAverageScore() < o2.getAverageScore()) {
                    return 1;
                } else {
                    return 0;
                }
            }
        });
        System.out.println("排序成功！");
    }
    // 查询学生信息
    public void queryStudent() {
        Scanner input = new Scanner(System.in);
        System.out.print("请输入要查询的学生学号：");
        String id = input.next();
        for (Student student : studentList) {
            if (id.equals(student.getId())) {
                System.out.println("学号\t年龄\t性别\t数学成绩\t语文成绩\t英语成绩\t平均分");
                System.out.println(student.getId() + "\t" + student.getAge() + "\t" + student.getGender() + "\t" + student.getMathScore() + "\t" + student.getChineseScore() + "\t" + student.getEnglishScore() + "\t" + student.getAverageScore());
                return;
            }
        }
        System.out.println("未找到该学生！");
    }
    // 修改学生信息
    public void modifyStudent() {
        Scanner input = new Scanner(System.in);
        System.out.print("请输入要修改的学生学号：");
        String id = input.next();
        for (Student student : studentList) {
            if (id.equals(student.getId())) {
                System.out.println("请输入修改后的学生信息：");
                System.out.print("年龄：");
                int age = input.nextInt();
                System.out.print("性别：");
                String gender = input.next();
                System.out.print("数学成绩：");
                double mathScore = input.nextDouble();
                System.out.print("语文成绩：");
                double chineseScore = input.nextDouble();
                System.out.print("英语成绩：");
                double englishScore = input.nextDouble();
                double averageScore = (mathScore + chineseScore + englishScore) / 3; // 计算平均分
                student.setAge(age);
                student.setGender(gender);
                student.setMathScore(mathScore);
                student.setChineseScore(chineseScore);
                student.setEnglishScore(englishScore);
                student.setAverageScore(averageScore);
                System.out.println("修改成功！");
                return;
            }
        }
        System.out.println("未找到该学生！");
    }
    // 删除学生信息
    public void deleteStudent() {
        Scanner input = new Scanner(System.in);
        System.out.print("请输入要删除的学生学号：");
        String id = input.next();
        for (Student student : studentList) {
            if (id.equals(student.getId())) {
                studentList.remove(student);
                System.out.println("删除成功！");
                return;
            }
        }
        System.out.println("未找到该学生！");
    }
}

最后，你可以编写一个主函数来测试学生管理系统的功能：

public class Main {
    public static void main(String[] args) {
        StudentManager studentManager = new StudentManager();
        Scanner input = new Scanner(System.in);
        while (true) {
            System.out.println("请选择操作：");
            System.out.println("1. 添加学生信息");
            System.out.println("2. 排序");
            System.out.println("3. 查询学生信息");
            System.out.println("4. 修改学生信息");
            System.out.println("5. 删除学生信息");
            System.out.println("0. 退出");
            int choice = input.nextInt();
            switch (choice) {
                case 1:
                    studentManager.addStudent();
                    break;
                case 2:
                    studentManager.sortStudent();
                    break;
                case 3:
                    studentManager.queryStudent();
                    break;
                case 4:
                    studentManager.modifyStudent();
                    break;
                case 5:
                    studentManager.deleteStudent();
                    break;
                case 0:
                    System.exit(0);
                    break;
                default:
                    System.out.println("无效的选择！");
                    break;
            }
        }
    }
}

希望这个代码可以帮助你完成学生管理系统的编写。