Class responsibilities and behavior in LLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Single Responsibility Principle

Which of the following best describes the Single Responsibility Principle (SRP) in class design?

A A class should have only one reason to change, meaning it should have only one responsibility.

B A class should handle multiple responsibilities to reduce the number of classes in the system.

C A class should inherit from multiple classes to gain various behaviors.

D A class should expose all its internal data to other classes for flexibility.

💡 Hint

Think about how many reasons a class should have to change.

The Single Responsibility Principle states that a class should have only one reason to change, meaning it should focus on a single responsibility or behavior.

❓ Architecture

intermediate

Class Behavior Distribution in a Library Management System

In a library management system, which class should be responsible for checking out a book to a user?

A The Book class, because it represents the book being checked out.

B The Library class, because it manages the collection of books.

C A separate CheckoutManager class, responsible for managing the checkout process.

D The User class, because it represents the person borrowing the book.

💡 Hint

Consider which class should handle the process involving multiple entities.

The CheckoutManager class is responsible for coordinating the checkout process, involving both the User and the Book, keeping responsibilities clear and separated.

❓ scaling

advanced

Scaling Class Responsibilities in a Messaging App

As a messaging app grows, which approach best helps to keep class responsibilities manageable and scalable?

A Avoid creating new classes and use global functions for all behaviors.

B Combine all message handling, user management, and notification logic into a single MessageService class.

C Let each class handle unrelated tasks to reduce the number of classes in the system.

D Divide responsibilities into specialized classes like MessageHandler, UserManager, and NotificationService.

💡 Hint

Think about how to keep classes focused and easy to maintain as the system grows.

Dividing responsibilities into specialized classes helps maintain clear boundaries, making the system easier to scale and maintain.

❓ tradeoff

advanced

Tradeoffs in Class Responsibility Granularity

What is a potential downside of making classes too fine-grained with very narrow responsibilities?

A It can lead to too many classes, making the system complex to navigate and maintain.

B It always improves performance by reducing class size.

C It reduces code reuse by forcing duplication in each class.

D It eliminates the need for interfaces or abstractions.

💡 Hint

Consider what happens when there are many small classes in a system.

While fine-grained classes improve focus, having too many can make the system harder to understand and maintain due to increased complexity.

❓ component

expert

Identifying Class Responsibilities in a Ride-Sharing System

In a ride-sharing system, which class should be responsible for calculating the fare of a ride?

A The Driver class, because the driver provides the service.

B The FareCalculator class, dedicated to computing fares based on ride details and pricing rules.

C The Ride class, because it represents the trip details and duration.

D The User class, because the user pays the fare.

💡 Hint

Think about separating calculation logic from data representation.

The FareCalculator class centralizes fare computation logic, keeping pricing rules separate from data classes like Ride or User.