Class design (Book, Member, Librarian, Loan) in LLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Identify the correct relationship between classes

In a library system, which relationship best describes how the Loan class relates to the Book and Member classes?

A Loan is unrelated to Book and Member and operates independently.

B Loan has a composition relationship with Book and Member, meaning Loan owns them and controls their lifecycle.

C Loan inherits from both Book and Member classes to combine their properties.

D Loan has an association relationship with Book and Member, meaning Loan references them but does not own them.

💡 Hint

Think about whether Loan should control the existence of Book or Member objects.

Loan represents a borrowing event and references existing Book and Member objects without owning them. Hence, it has an association relationship.

❓ Architecture

intermediate

Choose the best class to handle book availability status

In the library system, which class should be responsible for tracking whether a book is currently available for loan?

A The Loan class should track availability by checking if a book is loaned out.

B The Member class should track availability of books they want to borrow.

C The Book class should track its availability status directly.

D The Librarian class should maintain a separate list of available books.

💡 Hint

Consider which class naturally owns the state of the book itself.

The Book class represents the physical or digital book and should maintain its own availability status.

❓ scaling

advanced

Design consideration for handling thousands of loans

If the library system must handle thousands of simultaneous loans, which design choice improves scalability and performance?

A Use a database to store Loan records and query only active loans when needed.

B Store all Loan objects in memory within the Librarian class for quick access.

C Create a new Loan object for each request and keep them permanently in a list inside Member objects.

D Serialize all Loan objects to a file after each loan creation.

💡 Hint

Think about memory usage and data retrieval efficiency for large data.

Using a database allows efficient storage and querying of large numbers of loans without overloading memory.

❓ tradeoff

advanced

Tradeoff in making Member class responsible for loan history

What is a potential downside of storing all loan history inside each Member object?

A It can cause high memory usage if members have many loans.

B It simplifies querying loan history across all members.

C It improves performance by avoiding database queries.

D It prevents members from borrowing multiple books.

💡 Hint

Consider what happens when a member has a very long loan history.

Storing all loan history in memory per member can consume a lot of memory and reduce scalability.

❓ component

expert

Identify the correct sequence of actions when a book is loaned

What is the correct order of actions when a member borrows a book from the library?

A 3, 1, 2, 4

B 1, 2, 3, 4

C 2, 1, 3, 4

D 1, 3, 2, 4

💡 Hint

Think about the logical order to ensure the book can be loaned before creating records.

First check availability, then create loan, update status, and finally notify member.