Section-based revision questions and reasoning
On this page 10 headings
Question 1
A class manages seller details, inventory and sales reports. Which principle is at risk?
Answer and reasoning: SRP: the class has multiple reasons to change. Split seller, inventory and reporting responsibilities.
Question 2
A new payment provider requires editing Seller.processPayment(). Which principle suggests a redesign?
Answer and reasoning: DIP: Seller should depend on a payment abstraction. OCP also explains why extensibility is desirable.
Question 3
An e-book processor must provide an empty deliver() method. Why is that a problem?
Answer and reasoning: ISP: its interface includes a method irrelevant to the digital-order client.
Question 4
A subclass has the same method signature but throws an error for inputs accepted by its base class. Is LSP satisfied?
Answer and reasoning: No. Substitutability requires honoring the behavioral expectations of the base type.
Question 5
A client needs one operation to create an order, notify the seller and dispatch a parcel. Which pattern?
Answer and reasoning: Facade: it provides one simplified entry point to multiple subsystem steps.
Question 6
A product priced in dollars must get its cost in rupees from an existing ConversionCalculator it cannot call directly. Which pattern?
Answer and reasoning: Adapter (CostCalculatorAdapter): wraps the existing conversion library’s incompatible interface.
Question 7
A Book has mandatory ISBN, title and cost and optional author, published year and description. Which creational pattern?
Answer and reasoning: Builder: construct it step by step instead of using many telescoping constructors.
Question 8
Buyers should automatically learn about newly launched products. Which pattern?
Answer and reasoning: Observer: register buyers and notify them on a launch event.
Question 9
An order queue can be processed FIFO or by customer priority. Which pattern?
Answer and reasoning: Strategy: encapsulate the alternative algorithms behind a shared interface.
Question 10
You need to iterate over a tree without revealing its internal node representation. Which pattern?
Answer and reasoning: Iterator: separate traversal from collection representation.