Low-level design (LLD) for a ride-sharing service:

User accounts and authentication: The service will need to allow users to create accounts, log in, and log out. We will also need to implement measures to ensure the security of user accounts, such as password hashing and potentially two-factor authentication.
Rider and driver profiles: The service will need to store information about the riders and drivers, including their contact information, preferred payment methods, and ratings. This will likely involve creating separate tables or data structures for riders and drivers, with fields to store the relevant information.
Ride request and matching: The service will need to allow riders to request rides and drivers to accept or decline requests. This will involve creating forms and handling the associated server-side logic to match riders with nearby drivers.
Payment processing: The service will need to handle payment from riders to drivers, including processing and validating payment methods such as credit cards or mobile payments.
Rating and review system: The service will need to allow riders and drivers to rate and review each other after a ride is completed. This will involve creating forms and handling the associated server-side logic to store and display the ratings and reviews.
User interface: Finally, we will need to design the user interface for the service, including the layout, navigation, and any necessary graphics or styling. This will involve creating wireframes and mockups, as well as implementing the front-end code to bring the design to life.

Code

import java.util.*;

// Factory Interface to create key entities
interface RideSharingFactory {
    User createUser(String id, String name);
    Driver createDriver(String id, String name);
    Ride createRide(User user, Location pickupLocation);
    Notification createNotification(String message);
}

// Concrete Factory for the Ride Sharing Service
public class RideSharingServiceFactory implements RideSharingFactory {
    @Override
    public User createUser(String id, String name) {
        return new User(id, name);
    }

    @Override
    public Driver createDriver(String id, String name) {
        return new Driver(id, name);
    }

    @Override
    public Ride createRide(User user, Location pickupLocation) {
        return new Ride(user, pickupLocation);
    }

    @Override
    public Notification createNotification(String message) {
        return new Notification(message);
    }
}

// Observer pattern for notifications
interface Observer {
    void update(String message);
}

class UserObserver implements Observer {
    private User user;

    public UserObserver(User user) {
        this.user = user;
    }

    @Override
    public void update(String message) {
        System.out.println("Notification to User " + user.getName() + ": " + message);
    }
}

class DriverObserver implements Observer {
    private Driver driver;

    public DriverObserver(Driver driver) {
        this.driver = driver;
    }

    @Override
    public void update(String message) {
        System.out.println("Notification to Driver " + driver.getName() + ": " + message);
    }
}

// Subject interface for managing observers
interface Subject {
    void addObserver(Observer observer);
    void removeObserver(Observer observer);
    void notifyObservers(String message);
}

// Notification Service using Observer Pattern
public class NotificationService implements Subject {
    private List<Observer> observers = new ArrayList<>();

    @Override
    public void addObserver(Observer observer) {
        observers.add(observer);
    }

    @Override
    public void removeObserver(Observer observer) {
        observers.remove(observer);
    }

    @Override
    public void notifyObservers(String message) {
        for (Observer observer : observers) {
            observer.update(message);
        }
    }

    public void notifyNoDriversAvailable(User user) {
        notifyObservers("No drivers are available for user " + user.getName());
    }

    public void notifyRideAccepted(User user, Driver driver) {
        notifyObservers("Ride accepted by driver " + driver.getName() + " for user " + user.getName());
    }

    public void notifyRideCanceled(User user, Driver driver) {
        notifyObservers("Ride canceled for user " + user.getName() + " by driver " + driver.getName());
    }

    public void notifyRideCompleted(User user, Driver driver) {
        notifyObservers("Ride completed for user " + user.getName() + " by driver " + driver.getName());
    }
}

// Strategy interface for dynamic pricing
interface PricingStrategy {
    float calculatePrice(float distance);
}

// Concrete Strategy for normal pricing
class NormalPricingStrategy implements PricingStrategy {
    @Override
    public float calculatePrice(float distance) {
        return distance * 10; // Base rate per kilometer
    }
}

// Concrete Strategy for surge pricing
class SurgePricingStrategy implements PricingStrategy {
    @Override
    public float calculatePrice(float distance) {
        return distance * 15; // Increased rate per kilometer during peak hours
    }
}

// User class with notification observers
public class User {
    private String id;
    private String name;

    public User(String id, String name) {
        this.id = id;
        this.name = name;
    }

    public String getId() {
        return id;
    }

    public String getName() {
        return name;
    }
}

// Driver class with notification observers
public class Driver {
    private String id;
    private String name;

    public Driver(String id, String name) {
        this.id = id;
        this.name = name;
    }

    public String getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public void acceptRide(Ride ride) {
        ride.setDriver(this);
    }

    public void cancelRide(Ride ride) {
        ride.setDriver(null);
    }
}

// Ride class representing a ride request
public class Ride {
    private String id;
    private User user;
    private Driver driver;
    private Location pickupLocation;
    private Location dropoffLocation;
    private float distance;
    private float price;

    public Ride(User user, Location pickupLocation) {
        this.id = UUID.randomUUID().toString();
        this.user = user;
        this.pickupLocation = pickupLocation;
    }

    public String getId() {
        return id;
    }

    public User getUser() {
        return user;
    }

    public Driver getDriver() {
        return driver;
    }

    public void setDriver(Driver driver) {
        this.driver = driver;
    }

    public void setDropoffLocation(Location dropoffLocation) {
        this.dropoffLocation = dropoffLocation;
    }

    public void setDistance(float distance) {
        this.distance = distance;
    }

    public void setPrice(float price) {
        this.price = price;
    }
}

// Database classes for User, Driver, and Ride
public class UserDatabase {
    private Map<String, User> users = new HashMap<>();

    public void addUser(User user) {
        users.put(user.getId(), user);
    }

    public User getUser(String id) {
        return users.get(id);
    }
}

public class DriverDatabase {
    private Map<String, Driver> drivers = new HashMap<>();

    public void addDriver(Driver driver) {
        drivers.put(driver.getId(), driver);
    }

    public Driver getNearestDriver(Location location) {
        // Return the nearest available driver (implementation omitted)
        return null;
    }
}

public class RideDatabase {
    private Map<String, Ride> rides = new HashMap<>();

    public void addRide(Ride ride) {
        rides.put(ride.getId(), ride);
    }

    public Ride getRide(String id) {
        return rides.get(id);
    }

    public void updateRide(Ride ride) {
        rides.put(ride.getId(), ride);
    }

    public void removeRide(Ride ride) {
        rides.remove(ride.getId());
    }
}

// Payment processing class
public class PaymentProcessor {
    public void processPayment(User user, Driver driver, float amount) {
        System.out.println("Processing payment of " + amount + " from " + user.getName() + " to " + driver.getName());
    }
}

// Location class for managing ride pickup and dropoff points
public class Location {
    private String address;

    public Location(String address) {
        this.address = address;
    }

    public String getAddress() {
        return address;
    }
}

// Main class to run the Ride Sharing Service
public class RideSharingService {
    private UserDatabase userDatabase;
    private DriverDatabase driverDatabase;
    private RideDatabase rideDatabase;
    private PaymentProcessor paymentProcessor;
    private RatingService ratingService;
    private NotificationService notificationService;
    private PricingStrategy pricingStrategy;

    public RideSharingService(PricingStrategy pricingStrategy) {
        userDatabase = new UserDatabase();
        driverDatabase = new DriverDatabase();
        rideDatabase = new RideDatabase();
        paymentProcessor = new PaymentProcessor();
        ratingService = new RatingService();
        notificationService = new NotificationService();
        this.pricingStrategy = pricingStrategy;
    }

    public void signUpUser(User user) {
        userDatabase.addUser(user);
    }

    public void signUpDriver(Driver driver) {
        driverDatabase.addDriver(driver);
    }

    public void requestRide(String userId, Location pickupLocation) {
        User user = userDatabase.getUser(userId);
        if (user == null) {
            throw new IllegalArgumentException("Invalid user id");
        }

        Ride ride = new Ride(user, pickupLocation);
        rideDatabase.addRide(ride);

        Driver driver = driverDatabase.getNearestDriver(pickupLocation);
        if (driver == null) {
            notificationService.notifyNoDriversAvailable(user);
            return;
        }

        driver.acceptRide(ride);
        notificationService.notifyRideAccepted(user, driver);
    }

    public void completeRide(String rideId, Location dropoffLocation, float distance) {
        Ride ride = rideDatabase.getRide(rideId);
        if (ride == null) {
            throw new IllegalArgumentException("Invalid ride id");
        }

        User user = ride.getUser();
        Driver driver = ride.getDriver();
        float price = pricingStrategy.calculatePrice(distance);

        paymentProcessor.processPayment(user, driver, price);
        ride.setDropoffLocation(dropoffLocation);
        ride.setDistance(distance);
        ride.setPrice(price);

        rideDatabase.updateRide(ride);
        ratingService.addRating(user, driver, ride);
        notificationService.notifyRideCompleted(user, driver);
    }
}

// Example Main to run the service
public class Main {
    public static void main(String[] args) {
        PricingStrategy normalPricing = new NormalPricingStrategy();
        RideSharingService rideSharingService = new RideSharingService(normalPricing);

        // Set up users and drivers
        User user = new User("1", "Alice");
        Driver driver = new Driver("101", "Bob");
        Location pickupLocation = new Location("123 Main St");

        rideSharingService.signUpUser(user);
        rideSharingService.signUpDriver(driver);

        // Request a ride
        rideSharingService.requestRide(user.getId(), pickupLocation);
    }
}

Design (LLD) Ride sharing service - Machine Coding

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