PGStudent.java

// Postgraduate student class
// Inherits from Student and implements calculateGrade() based on PG rules
public class PGStudent extends Student {

    // Constructor calls base class constructor to initialize fields
    public PGStudent(String name, int rollNo, int marks) {
        super(name, rollNo, marks);
    }

    // Calculate grade for PG student
    @Override
    public char calculateGrade() {
        if (marks >= 90) return 'A';
        else if (marks >= 75) return 'B';
        else if (marks >= 60) return 'C';
        else return 'F';
    }

    // Display PG student details
    @Override
    public void display() {
        System.out.println("PG Student | Name: " + name +
                "  Roll: " + rollNo +
                "  Marks: " + marks +
                "  Grade: " + calculateGrade());
    }
}