Creational patterns (Singleton, Factory, Builder) in Software Engineering - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the Singleton pattern?

The Singleton pattern ensures a class has only one instance and provides a global point to access it. It is useful when exactly one object is needed to coordinate actions across a system.

beginner

How does the Factory pattern help in object creation?

The Factory pattern creates objects without exposing the creation logic to the client. It lets the client use a common interface to create different types of objects, making the code flexible and easier to maintain.

beginner

What problem does the Builder pattern solve?

The Builder pattern separates the construction of a complex object from its representation. It allows creating different representations step-by-step, making it easier to build objects with many parts or options.

intermediate

Why use the Singleton pattern instead of a global variable?

Singleton controls the instance creation and can add behavior like lazy initialization or thread safety. Unlike global variables, it encapsulates the instance and can be extended or modified without affecting global state directly.

beginner

Give a real-life example of the Factory pattern.

Imagine a car factory that produces different car models. The factory decides which car to build based on customer choice, hiding the details of how each car is made. The customer just requests a car type and gets the right model.

Which creational pattern ensures only one instance of a class exists?

A Factory

B Builder

C Singleton

D Observer

The Singleton pattern restricts a class to a single instance.

What is the main benefit of the Factory pattern?

A Creates objects without exposing creation logic

B Ensures only one instance exists

C Builds complex objects step-by-step

D Manages object lifecycle automatically

Factory hides the creation logic and provides a common interface.

Which pattern is best for creating complex objects with many parts?

A Factory

B Builder

C Singleton

D Decorator

Builder separates construction from representation for complex objects.

What does the Singleton pattern provide besides a single instance?

A Global access point

B Multiple object types

C Step-by-step construction

D Automatic memory management

Singleton provides a global point to access the single instance.

In the Factory pattern, who decides which object to create?

A Client directly

B Builder director

C Singleton instance

D Factory class

The Factory class decides which object to create based on input.

Explain the differences between Singleton, Factory, and Builder patterns with simple examples.

Think about how each pattern controls object creation differently.

Describe a situation where using the Builder pattern is better than the Factory pattern.

Consider complexity and flexibility in object creation.