import java.io.*; import java.util.ArrayList; import java.util.InputMismatchException; import java.util.Scanner;

// Student class class Student implements Serializable { private static final long serialVersionUID = 1L; int studentID; String name; String grade;

public Student(int studentID, String name, String grade) {
    this.studentID = studentID;
    this.name = name;
    this.grade = grade;
}

@Override
public String toString() {
    return "StudentID: " + studentID + ", Name: " + name + ", Grade: " + grade;
}

}

// Employee class class Employee implements Serializable { private static final long serialVersionUID = 1L; String name; int id; String designation; double salary;

public Employee(String name, int id, String designation, double salary) {
    this.name = name;
    this.id = id;
    this.designation = designation;
    this.salary = salary;
}

@Override
public String toString() {
    return "ID: " + id + ", Name: " + name + ", Designation: " + designation + ", Salary: " + salary;
}

}

public class NimbusApplication {

// Part a: Sum of integers using autoboxing/unboxing
public static void sumIntegers(Scanner sc) {
    ArrayList<Integer> numbers = new ArrayList<>();
    System.out.println("Enter integers separated by space:");
    String input = sc.nextLine();
    String[] parts = input.split("\\s+");

    for (String s : parts) {
        try {
            int num = Integer.parseInt(s);
            numbers.add(num); // Autoboxing
        } catch (NumberFormatException e) {
            System.out.println("Invalid number skipped: " + s);
        }
    }

    int sum = 0;
    for (Integer n : numbers) {
        sum += n; // Unboxing
    }

    System.out.println("Sum of entered integers: " + sum);
}

// Part b: Student serialization/deserialization
public static void studentSerialization(Scanner sc) {
    try {
        System.out.print("Enter Student ID: ");
        int id = sc.nextInt();
        sc.nextLine(); // consume newline
        System.out.print("Enter Student Name: ");
        String name = sc.nextLine();
        System.out.print("Enter Grade: ");
        String grade = sc.nextLine();

        Student student = new Student(id, name, grade);

        // Serialize student
        try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("student.dat"))) {
            oos.writeObject(student);
            System.out.println("Student object serialized successfully.");
        }

        // Deserialize student
        try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream("student.dat"))) {
            Student deserializedStudent = (Student) ois.readObject();
            System.out.println("Deserialized Student: " + deserializedStudent);
        }

    } catch (InputMismatchException e) {
        System.out.println("Invalid input. Please enter correct data types.");
        sc.nextLine(); // clear buffer
    } catch (IOException | ClassNotFoundException e) {
        e.printStackTrace();
    }
}

// Part c: Menu-based Employee Management System
public static void employeeManagement(Scanner sc) {
    String fileName = "employees.dat";
    ArrayList<Employee> employees = new ArrayList<>();

    // Load existing employees
    try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream(fileName))) {
        employees = (ArrayList<Employee>) ois.readObject();
    } catch (FileNotFoundException | EOFException e) {
        // First run or empty file, ignore
    } catch (IOException | ClassNotFoundException e) {
        e.printStackTrace();
    }

    boolean exit = false;
    while (!exit) {
        System.out.println("\nEmployee Management System Menu:");
        System.out.println("1. Add Employee");
        System.out.println("2. Display All Employees");
        System.out.println("3. Exit");
        System.out.print("Enter choice: ");

        int choice;
        try {
            choice = sc.nextInt();
            sc.nextLine(); // consume newline
        } catch (InputMismatchException e) {
            System.out.println("Invalid input. Please enter a number.");
            sc.nextLine();
            continue;
        }

        switch (choice) {
            case 1:
                try {
                    System.out.print("Enter Employee ID: ");
                    int id = sc.nextInt();
                    sc.nextLine();
                    System.out.print("Enter Name: ");
                    String name = sc.nextLine();
                    System.out.print("Enter Designation: ");
                    String designation = sc.nextLine();
                    System.out.print("Enter Salary: ");
                    double salary = sc.nextDouble();
                    sc.nextLine();

                    Employee emp = new Employee(name, id, designation, salary);
                    employees.add(emp);

                    // Save employees to file
                    try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(fileName))) {
                        oos.writeObject(employees);
                    }

                    System.out.println("Employee added successfully.");
                } catch (InputMismatchException e) {
                    System.out.println("Invalid input. Employee not added.");
                    sc.nextLine();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                break;

            case 2:
                if (employees.isEmpty()) {
                    System.out.println("No employees found.");
                } else {
                    System.out.println("Employee List:");
                    for (Employee e : employees) {
                        System.out.println(e);
                    }
                }
                break;

            case 3:
                exit = true;
                System.out.println("Exiting Employee Management System.");
                break;

            default:
                System.out.println("Invalid choice. Try again.");
        }
    }
}

public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    System.out.println("=== Nimbus Java Program ===");
    boolean exitProgram = false;

    while (!exitProgram) {
        System.out.println("\nSelect Part to Execute:");
        System.out.println("1. Sum of Integers (Autoboxing/Unboxing)");
        System.out.println("2. Student Serialization/Deserialization");
        System.out.println("3. Employee Management System (File Handling)");
        System.out.println("4. Exit");
        System.out.print("Enter choice: ");

        int choice;
        try {
            choice = sc.nextInt();
            sc.nextLine();
        } catch (InputMismatchException e) {
            System.out.println("Invalid input. Please enter a number.");
            sc.nextLine();
            continue;
        }

        switch (choice) {
            case 1:
                sumIntegers(sc);
                break;
            case 2:
                studentSerialization(sc);
                break;
            case 3:
                employeeManagement(sc);
                break;
            case 4:
                exitProgram = true;
                System.out.println("Exiting Nimbus Application.");
                break;
            default:
                System.out.println("Invalid choice. Try again.");
        }
    }

    sc.close();
}

}