StudentResultSystem.java

import java.util.Scanner;

// 1. Interface (As per diagram: Exam)
interface Exam {
    void percentCal();
}

// 2. Base Class (As per diagram: Student)
class Student {
    private String name;
    private int rollNo;
    private int marks1;
    private int marks2;

    // Parameterized Constructor
    public Student(String name, int rollNo, int marks1, int marks2) {
        this.name = name;
        this.rollNo = rollNo;
        this.marks1 = marks1;
        this.marks2 = marks2;
    }

    // Protected getters allow the Result subclass to safely access the marks
    protected int getMarks1() { return marks1; }
    protected int getMarks2() { return marks2; }

    public void show() {
        System.out.println("Student Name: " + name);
        System.out.println("Roll Number: " + rollNo);
        System.out.println("Marks in Paper 1: " + marks1);
        System.out.println("Marks in Paper 2: " + marks2);
    }
}

// 3. Derived Class (As per diagram: Result)
class Result extends Student implements Exam {
    private double percentage;

    public Result(String name, int rollNo, int marks1, int marks2) {
        super(name, rollNo, marks1, marks2); // Call the parent constructor
    }

    // Implementing the interface method
    @Override
    public void percentCal() {
        // Using getters to maintain encapsulation from the parent class
        percentage = (getMarks1() + getMarks2()) / 2.0;
    }

    // Displaying final result
    public void perDisplay() {
        show(); // Inherited method from Student
        percentCal(); // Implemented method from Exam interface
        System.out.println("Total Percentage: " + percentage + "%");
    }
}

// 4. Main Driver Class (PascalCase)
public class StudentResultSystem {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.println("--- Student Result Calculation System ---");
        
        System.out.print("Enter your name: ");
        String name = scanner.nextLine();
        
        System.out.print("Enter your roll number: ");
        int rollNo = getValidInt(scanner);
        
        System.out.print("Enter your marks for Paper 1: ");
        int marks1 = getValidInt(scanner);
        
        System.out.print("Enter your marks for Paper 2: ");
        int marks2 = getValidInt(scanner);

        // Instantiating the Result object
        System.out.println("\n=====================================");
        Result studentResult = new Result(name, rollNo, marks1, marks2);
        studentResult.perDisplay();
        System.out.println("=====================================");
        
        scanner.close();
    }

    // Helper Method to prevent Scanner crashes during input
    private static int getValidInt(Scanner scanner) {
        while (!scanner.hasNextInt()) {
            System.out.print("Invalid input. Please enter a valid number: ");
            scanner.next(); // Consume invalid input
        }
        return scanner.nextInt();
    }
}