OOPS-lab-codes/OnlinePaymentSystem.java

import java.util.Scanner;

// -------- BASE CLASS --------
class Payment {

    double amount;

    Payment(double amount) {
        this.amount = amount;
    }

    double processPayment() {
        return amount;
    }
}

// -------- SUB CLASS : CREDIT CARD --------
class CreditCardPayment extends Payment {

    CreditCardPayment(double amount) {
        super(amount);
    }

    double processPayment() {
        return amount + (amount * 0.02); // 2% service charge
    }
}

// -------- SUB CLASS : UPI --------
class UPIPayment extends Payment {

    UPIPayment(double amount) {
        super(amount);
    }

    double processPayment() {
        return amount + 5; // Flat ₹5 charge
    }
}

// -------- SUB CLASS : NET BANKING --------
class NetBankingPayment extends Payment {

    NetBankingPayment(double amount) {
        super(amount);
    }

    double processPayment() {
        return amount + (amount * 0.015); // 1.5% service charge
    }
}

// -------- MAIN CLASS --------
public class OnlinePaymentSystem {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.print("Enter payment amount: ");
        double amount = sc.nextDouble();

        System.out.println("\nChoose Payment Method:");
        System.out.println("1. Credit Card");
        System.out.println("2. UPI");
        System.out.println("3. Net Banking");
        System.out.print("Enter choice: ");
        int choice = sc.nextInt();

        Payment payment; // Base class reference

        switch (choice) {
            case 1:
                payment = new CreditCardPayment(amount);
                break;
            case 2:
                payment = new UPIPayment(amount);
                break;
            case 3:
                payment = new NetBankingPayment(amount);
                break;
            default:
                System.out.println("Invalid choice");
                sc.close();
                return;
        }

        // Dynamic method dispatch
        double finalAmount = payment.processPayment();

        System.out.println("\nFinal Payable Amount: ₹" + finalAmount);

        sc.close();
    }
}