OOP - lesson 5 | HackIndia Skills

OOP - lesson 5 | HackIndia Skills | HackIndia

Example

Payment example

Here is a small Java example. The OrderService does not know whether payment is UPI or cash. It only knows that payment can be paid.

This makes the feature easy to extend and easy to test.

interface PaymentMethod {
    boolean pay(int amountInRupees);
}

class UpiPayment implements PaymentMethod {
    private final String upiId;

    UpiPayment(String upiId) {
        this.upiId = upiId;
    }

    public boolean pay(int amountInRupees) {
        System.out.println("Collecting Rs " + amountInRupees + " using UPI: " + upiId);
        return true;
    }
}

class CashPayment implements PaymentMethod {
    public boolean pay(int amountInRupees) {
        System.out.println("Collect Rs " + amountInRupees + " at counter");
        return true;
    }
}

class OrderService {
    private final PaymentMethod paymentMethod;

    OrderService(PaymentMethod paymentMethod) {
        this.paymentMethod = paymentMethod;
    }

    void placeOrder(int amountInRupees) {
        boolean paid = paymentMethod.pay(amountInRupees);
        if (paid) {
            System.out.println("Order placed");
        }
    }
}

public class Main {
    public static void main(String[] args) {
        PaymentMethod payment = new UpiPayment("student@upi");
        OrderService orderService = new OrderService(payment);
        orderService.placeOrder(120);
    }
}

Polymorphism through interfaces

One idea

Why it helps

When to use it

Payment example

Use AI carefully

Common mistake

Show it in your repo

Do this now

Quick check