Creational Design Pattern

Which of the following creational design patterns shares the goal of hiding the object creation logic from the client code?

• Factory

• Builder

• Prototype

• Abstract Factory

• Singleton

Answer explanation

Both Factory Method and Abstract Factory hide the object creation logic and provide an interface for clients to interact with the created objects.

When might you choose the Prototype pattern over the Factory Method pattern?

• When you need to create complex objects with many configurable parts.

• When you need to ensure only one instance of an object exists.

• When you want to defer the decision of which object to create until runtime.

• When you need a central registry to manage all created objects.

Answer explanation

Prototype excels at creating complex objects by cloning existing ones, while Factory Method focuses on creating new objects based on a type.

The Factory Method pattern often relies on inheritance to differentiate between object types. Can the Builder pattern also leverage inheritance for similar purposes?

• No, Builder uses composition to define object structures.

• Yes, Builder subclasses can define specific construction steps for different object types.

• Builder relies solely on interfaces to define object creation logic.

• Both inheritance and composition are commonly used in Builder.

Answer explanation

Builder uses composition with different builder methods to define object structures, not inheritance.

Imagine a system where you need to create different shapes (Square, Circle) based on user input. Which creational pattern would be most suitable, considering the Factory Method?

• Singleton

• Abstract Factory

• Prototype

• Builder

Answer explanation

Abstract Factory allows creating families of related objects (like shapes) based on a user choice.

The Factory Method class typically defines a method to create objects. Can the Singleton pattern also define a similar method for controlled access to its single instance?

• No, Singleton relies on a static field for access, not a method.

• Yes, the Singleton class can have a getInstance() method for controlled access.

• Singleton uses a factory class to delegate object creation.

• Both Factory Method and Singleton hide the object creation logic completely.

Answer explanation

Singleton often defines a getInstance() method to provide controlled access to its single instance.

When using the Factory Method pattern, the client code interacts with the created objects through an interface. Does the Builder pattern also enforce this concept?

• No, Builder clients directly interact with concrete builder classes.

• Yes, Builder provides an interface to define the object structure, which clients use.

• Factory Method allows concrete classes to be returned, while Builder always returns interfaces.

• Both patterns hide the implementation details of the created objects.

Answer explanation

Builder defines an interface for object construction, similar to Factory Method using interfaces for created objects.

Compared to the Factory Method, the Abstract Factory pattern introduces an additional layer of abstraction. What benefit does this extra layer provide?

• It simplifies the creation of complex objects with many parts.

• It allows creating families of related objects based on a type.

• It reduces the number of concrete factory classes required.

• It enforces code reusability for object creation logic.

Answer explanation

Abstract Factory provides a central location to define families of related objects, promoting code reuse and flexibility.

The Factory Method pattern can be seen as a simpler version of the Abstract Factory pattern. Can the Prototype pattern also be considered a simpler alternative to the Builder pattern?

• No, Prototype offers more control over object configuration compared to Builder.

• Yes, Prototype allows for cloning existing objects, similar to Builder's step-by-step construction.

• Builder is simpler because it doesn't require defining separate classes for different object types.

• Both Prototype and Builder are complex patterns with many moving parts.

Answer explanation

While both define object creation logic, Prototype offers a simpler approach by cloning existing objects, whereas Builder provides finer-grained control through separate construction steps.

When might you choose a combination of Factory Method and Singleton patterns?

• To create a thread-safe factory that always returns the same instance.

• To simplify object creation logic within a single class with controlled access.

• When you need a central registry to manage all created objects by the factory.

• The combination is generally not recommended as their purposes don't align well.

Answer explanation

Factory Method focuses on creating objects based on types, while Singleton ensures only one instance exists. Combining them wouldn't provide a clear benefit and might introduce complexity.

Which of the following creational design patterns are most focused on hiding the implementation details of object creation from the client code?

• Singleton

• Factory Method

• Builder

• Prototype

Answer explanation

Singleton, Factory Method, and Builder all aim to hide the object creation logic, providing a cleaner interface for clients to interact with the created objects. Prototype exposes the creation logic to some extent, as it relies on cloning existing objects.