costam25.java

import java.util.Map;
import java.util.Scanner;
import java.util.TreeMap;

public class Main {
    public static void main(String[] args) {
        StudentGrades app = new StudentGrades();
        while (true) {
            System.out.println("1. Add student");
            System.out.println("2. Remove student");
            System.out.println("3. Change grade");
            System.out.println("4. Print grades");
            System.out.println("5. Exit");
            System.out.print("Enter your choice: ");
            int choice = app.getInput().nextInt();
            app.getInput().nextLine();
            if (choice == 1) {
                app.addStudent();
            } else if (choice == 2) {
                app.removeStudent();
            } else if (choice == 3) {
                app.changeGrade();
            } else if (choice == 4) {
                app.printGrades();
            } else {
                break;
            }
        }
    }
}

class StudentGrades {
    private Map<String, String> students = new TreeMap<>();
    private Scanner input = new Scanner(System.in);

    public Scanner getInput() {
        return input;
    }

    public void addStudent() {
        System.out.print("Enter student's name: ");
        String name = input.nextLine();
        System.out.print("Enter student's grade: ");
        String grade = input.nextLine();
        students.put(name, grade);
    }

    public void removeStudent() {
        System.out.print("Enter student's name: ");
        String name = input.nextLine();
        students.remove(name);
    }

    public void changeGrade() {
        System.out.print("Enter student's name: ");
        String name = input.nextLine();
        System.out.print("Enter new grade: ");
        String grade = input.nextLine();
        students.put(name, grade);
    }

    public void printGrades() {
        System.out.println("Grades:");
        for (Map.Entry<String, String> entry : students.entrySet()) {
            System.out.println(entry.getKey() + ": " + entry.getValue());
        }
    }
}