Detailed explanation of implementation of Java writing console student status management system

package student_status_management_system;

public class Student {
    private String student_number;
    private String name;
    private String age;
    private String address;

    public Student() {
    }

    public Student(String student_number, String name, String age, String address) {
        this.student_number = student_number;
        this.name = name;
        this.age = age;
        this.address = address;
    }

    public String getStudent_number() {
        return student_number;
    }

    public void setStudent_number(String student_number) {
        this.student_number = student_number;
    }

    public String getName() {
        return name;
    }

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

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

public static boolean repetition(ArrayList<Student>array,String studentnumber){
        boolean flag = false;
        for (int i = 0;i<array.size();i++){
            Student s = array.get(i);
            if (s.getStudent_number().equals(studentnumber)){
                flag = true;
                break;
            }
        }

        return flag;
    }

public static void addStudent(ArrayList<Student> array) {

        String studentnumber;
        Scanner sc = new Scanner(System.in);

        while (true) {
            System.out.println("请输入学生学号：");
             studentnumber = sc.nextLine();

            boolean flag = repetition(array, studentnumber);
            if (flag) {
                System.out.println("该学号已存在！请重新输入！");
            }
            else {
                break;
            }
        }
        System.out.println("请输入学生姓名：");
        String name = sc.nextLine();

        System.out.println("请输入学生年龄：");
        String age = sc.nextLine();

        System.out.println("请输入学生居住地：");
        String address = sc.nextLine();

        //创建学生对象，把键盘录入的学生信息赋值给学生对象的成员变量

        Student s = new Student();
        s.setStudent_number(studentnumber);
        s.setName(name);
        s.setAge(age);
        s.setAddress(address);

        //将信息添加到集合
        array.add(s);
        System.out.println("添加成功！");

    }

public static void updateStudent(ArrayList<Student> array) {

        int index = -1;


        Scanner sc = new Scanner(System.in);
        System.out.println("请输入你要修改的学生的学号：");
        String id = sc.nextLine();

        for (int i = 0; i < array.size(); i++) {
            Student student = array.get(i);
            if (student.getStudent_number().equals(id)) {
                index = i;

                break;
            }
        }

        if (index == -1) {
            System.out.println("该学号不存在！");
        } else {

            System.out.println("请输入新的学生姓名：");
            String name = sc.nextLine();

            System.out.println("请输入新的学生年龄：");
            String age = sc.nextLine();

            System.out.println("请输入新的学生居住地：");
            String address = sc.nextLine();

            Student s = new Student();

            s.setStudent_number(id);
            s.setName(name);
            s.setAge(age);
            s.setAddress(address);

            array.set(index, s);
            System.out.println("修改成功！");
        }

    }

public static void deleteStudent(ArrayList<Student> array) {

        int index = -1; //定义索引
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入你要删除的学生的学号：");
        String id = sc.nextLine();

        for (int i = 0; i < array.size(); i++) {
            Student s = array.get(i);
            if (s.getStudent_number().equals(id)) {
                index = i;
                break;
            }


        }

        if (index == -1) {
            System.out.println("该学号不存在！");
        } else {
            array.remove(index);
            System.out.println("删除成功！");
        }

    }

public static void findAllStudent(ArrayList<Student> array) {
        //显示表头
        if (array.size() == 0) {
            System.out.println("你还没有输入信息！");
            return;//阻止程序往下执行
        }
        System.out.println("学号\t\t\t\t姓名\t\t年龄\t\t\t居住地");
        for (int i = 0; i < array.size(); i++) {
            Student s = array.get(i);
            System.out.println(s.getStudent_number() + "\t\t" + s.getName() + "\t\t" + s.getAge() + "岁" + "\t\t" + s.getAddress());
        }
    }

public static void main(String[] args) {
        //创建集合，储存学生信息
        ArrayList<Student> array = new ArrayList<>();

        while (true) {
            System.out.println("——————欢迎来到学生学籍管理系统——————");
            System.out.println("1 添加学生");
            System.out.println("2 修改学生");
            System.out.println("3 删除学生");
            System.out.println("4 查看所有学生");
            System.out.println("5 退出系统");
            //主界面
            Scanner sc = new Scanner(System.in);
            System.out.println("请输入你要进行的操作（数字序号）：");
            String line = sc.nextLine();

            switch (line) {
                case "1":
                    addStudent(array);
                    break;
                case "2":
                    updateStudent(array);
                    break;
                case "3":
                    deleteStudent(array);
                    break;

                case "4":
                    findAllStudent(array);
                    break;

                case "5":
                    System.out.println("再见！");
                    System.exit(0);//JVM退出


            }

        }
    }