Unit 10: Nested Classes & Lambda Expressions

🏢 How Swiggy Calculates Your Delivery Fee in One Line of Java

Every time you order biryani on Swiggy, a delivery fee is calculated based on distance, restaurant load, surge pricing, and weather. Before Java 8, Swiggy's engineering team would have written something like this:

Java — Before (Anonymous Class)
interface FeeCalculator {
    double calculate(Order order);
}

FeeCalculator calculator = new FeeCalculator() {
    @Override
    public double calculate(Order order) {
        return order.getDistance() * 2.5;
    }
};

With Java 8 lambdas, this becomes one line:

Java — After (Lambda)
Function<Order, Double> feeCalculator = order -> order.getDistance() * 2.5;

One line of Java replacing 20 lines of anonymous class boilerplate. That's not just syntactic sugar — it's a paradigm shift. Lambdas make Java code more readable, more composable, and more functional. Every major Indian tech company — Swiggy, Zomato, Flipkart, Paytm, PhonePe, Razorpay — writes Java this way today.