Creational patterns (Singleton, Factory, Builder) in Software Engineering - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Singleton Pattern Behavior

What is the main purpose of the Singleton pattern in software design?

A To ensure a class has only one instance and provide a global point of access to it.

B To create objects without specifying the exact class of object to create.

C To separate the construction of a complex object from its representation.

D To allow multiple instances of a class with different configurations.

💡 Hint

Think about controlling the number of instances of a class.

The Singleton pattern restricts a class to a single instance and provides a global access point to that instance, ensuring controlled access and resource management.

📋 Factual

intermediate

Factory Pattern Purpose

Which statement best describes the Factory pattern?

A It provides an interface for creating objects but lets subclasses decide which class to instantiate.

B It ensures only one instance of a class exists throughout the application.

C It builds complex objects step by step, allowing different representations.

D It allows an object to alter its behavior when its internal state changes.

💡 Hint

Focus on object creation and subclass responsibility.

The Factory pattern defines an interface for creating objects but lets subclasses decide which class to instantiate, promoting loose coupling.

🔍 Analysis

advanced

Builder Pattern Application

Given a scenario where you need to create different types of complex documents with many optional parts, which creational pattern is most suitable?

A Factory, because it decides which document subclass to instantiate.

B Builder, because it constructs complex objects step by step allowing different representations.

C Singleton, because it controls the number of document instances.

D Prototype, because it clones existing document instances.

💡 Hint

Think about building complex objects with many optional parts.

The Builder pattern is ideal for constructing complex objects step by step, especially when the object can have different representations or optional parts.

❓ Comparison

advanced

Comparing Singleton and Factory Patterns

Which of the following correctly contrasts the Singleton and Factory patterns?

A Singleton creates multiple objects; Factory restricts to one instance.

B Singleton and Factory both ensure only one instance exists.

C Singleton builds complex objects stepwise; Factory provides global access.

D Singleton controls instance count; Factory controls object creation type.

💡 Hint

Focus on what each pattern controls or manages.

Singleton ensures only one instance of a class exists, while Factory controls which type of object to create without specifying the exact class.

❓ Reasoning

expert

Singleton Pattern Thread Safety Challenge

Consider a Singleton implementation in a multi-threaded environment. What is the main risk if the Singleton is not implemented with thread safety?

A The Singleton will automatically become a Factory, creating different objects.

B The Singleton instance will never be created, causing null reference errors.

C Multiple instances of the Singleton class may be created, breaking the pattern's intent.

D The Singleton instance will be shared safely without any issues.

💡 Hint

Think about what happens when two threads try to create the instance at the same time.

Without thread safety, multiple threads can create separate instances simultaneously, violating the Singleton pattern's guarantee of a single instance.