Классы

import java.util.Scanner;
 
public class Task_0021 {
 
    public static Student[] s;
    public static Scanner scan;
    public enum Specialty {
        Computer_Science("Computer Science"), 
        System_analysis("System analysis"), 
        Software_engineering("Software engineering");
                      
        private final String value;
 
        Specialty(String value) {
            this.value = value;
        }
    
        public String getValue() {
        return value;
        }
 
    };
    
    public static void main(String[] args) {
        scan = new Scanner(System.in);
        System.out.print("Enter the number of students: ");
        int n = scan.nextInt();
        s = new Student[n];
        int k;
        do {
            System.out.println("");
            System.out.println("Select an action:");
            System.out.println("[1] - Add student;");
            System.out.println("[2] - Print information;");
            System.out.println("[3] - Percentage of the best students;");
            System.out.println("[4] - Students who received a grade of 5 in physics;");
            System.out.println("[0] - Exit.");
            System.out.println("");
            System.out.println("Enter a value: ");
            k = scan.nextInt();
            System.out.println("");
            switch (k) {
                case 1: studentsCreate(s); break;
                case 2: studentsPrint(s); break;
                case 3: System.out.printf("Percentage of the best students - %6.2f", studentsTop(s)); break; 
                case 4: System.out.println("Students who received a grade of 5 in physics: "); studentsPhysics(s); break;
                case 0: break;
                default: System.out.println("You have entered an incorrect value! Number should be the number of the selected menu item."); break;
            }
        } while (k != 0);
    }
 
    private static void studentsCreate(Student[] s) {
        int specialty;
        for (int i = 0; i < s.length; i++) {
            s[i] = new Student();
            System.out.printf("Student № %3d:\n", i + 1);
            System.out.print("  Surname: ");
            scan.nextLine();
            s[i].setSurname(scan.nextLine());
            System.out.print("  Course: ");
            s[i].setCourse(scan.nextInt());
            System.out.println("  Specialty:");
            System.out.println("    0. Computer Science");
            System.out.println("    1. System analysis");
            System.out.println("    2. Software engineering");
            specialty = (scan.nextInt());
            switch (specialty) {
                case 0: s[i].setSpecialty(Specialty.Computer_Science); break;
                case 1: s[i].setSpecialty(Specialty.System_analysis); break;
                case 2: s[i].setSpecialty(Specialty.Software_engineering); break;
            }
            System.out.print("  Physics: ");
            s[i].setPoints_physics(scan.nextInt());
            System.out.print("  Maths: ");
            s[i].setPoints_maths(scan.nextInt());
            System.out.print("  CS: ");
            s[i].setPoints_cs(scan.nextInt());
        }
    }
    
    private static void studentsPrint(Student[] s) {
        System.out.println("| № | Surname | Course |     Specialty      | Physics | Math | CS |");
        for (int i = 0; i < s.length; i++) {
            System.out.printf("|%3d|%9s|%8d|%20s|%9d|%6d|%4d|", 
                    i + 1, s[i].getSurname(), s[i].getCourse(), s[i].getSpecialty().value, 
                    s[i].getPoints_physics(), s[i].getPoints_maths(), s[i].getPoints_cs());
        }
    }
 
    private static double studentsTop(Student[] s) {
        int count = 0;
        for (Student item : s) {
            if (item.getPoints_maths() == 5 && item.getPoints_physics() == 5 && item.getPoints_cs() == 5) {
                count++;
            }
        }
        return (double) count / s.length * 100;
    }
 
    private static void studentsPhysics(Student[] s) {
        for (Student item : s) {
            if (item.getPoints_physics() == 5) {
                System.out.println(item.getSurname());
            }
        }
    }
 
}   
 
class Student {
    private String surname;
    private int course;
    private Task_0021.Specialty specialty;
    private int points_physics;
    private int points_maths;
    private int points_cs;
 
    public String getSurname() {
        return surname;
    }
 
    public void setSurname(String surname) {
        this.surname = surname;
    }
 
    public int getCourse() {
        return course;
    }
 
    public void setCourse(int course) {
        this.course = course;
    }
 
    public Task_0021.Specialty getSpecialty() {
        return specialty;
    }
 
    public void setSpecialty(Task_0021.Specialty specialty) {
        this.specialty = specialty;
    }
 
    public int getPoints_physics() {
        return points_physics;
    }
 
    public void setPoints_physics(int points_physics) {
        this.points_physics = points_physics;
    }
 
    public int getPoints_maths() {
        return points_maths;
    }
 
    public void setPoints_maths(int points_maths) {
        this.points_maths = points_maths;
    }
 
    public int getPoints_cs() {
        return points_cs;
    }
 
    public void setPoints_cs(int points_cs) {
        this.points_cs = points_cs;
    }
 
}