Questions and answers related to Design Pattern

Here are questions and answers related to Design Pattern:

General Questions

  1. Q: What is a design pattern?
    • A design pattern is a reusable solution to a common problem in software design.
  2. Q: Why are design patterns important?
    • They provide proven solutions, improve code readability, and promote best practices.
  3. Q: How are design patterns categorized?
    • Design patterns are categorized into three types: Creational, Structural, and Behavioral.
  4. Q: What is the difference between a design pattern and an algorithm?
    • A design pattern is a high-level solution to a design problem, while an algorithm is a step-by-step procedure for solving a computational problem.
  5. Q: What are the benefits of using design patterns?
    • Benefits include code reusability, scalability, maintainability, and improved communication among developers.

Creational Design Patterns

  1. Q: What are creational design patterns?
    • Creational patterns deal with object creation mechanisms, trying to create objects in a manner suitable to the situation.
  2. Q: What is the Singleton pattern?
    • The Singleton pattern ensures that a class has only one instance and provides a global point of access to it.
  3. Q: What is the Factory Method pattern?
    • The Factory Method pattern provides an interface for creating objects but allows subclasses to alter the type of objects that will be created.
  4. Q: What is the Abstract Factory pattern?
    • The Abstract Factory pattern provides an interface for creating families of related or dependent objects without specifying their concrete classes.
  5. Q: What is the Builder pattern?
    • The Builder pattern separates the construction of a complex object from its representation, allowing the same construction process to create different representations.
  6. Q: What is the Prototype pattern?
    • The Prototype pattern creates new objects by copying an existing object, known as the prototype.
  7. Q: When should you use the Singleton pattern?
    • Use the Singleton pattern when you need to ensure that only one instance of a class exists and provide a global point of access to it.
  8. Q: What are the drawbacks of the Singleton pattern?
    • It can make unit testing difficult and may introduce global state into an application.
  9. Q: How does the Factory Method differ from the Abstract Factory?
    • The Factory Method creates one type of object, while the Abstract Factory creates families of related objects.
  10. Q: What are the advantages of the Builder pattern?
    • It simplifies the creation of complex objects and makes the code more readable and maintainable.

Structural Design Patterns

  1. Q: What are structural design patterns?
    • Structural patterns deal with object composition and relationships to form larger structures.
  2. Q: What is the Adapter pattern?
    • The Adapter pattern allows incompatible interfaces to work together by converting one interface into another.
  3. Q: What is the Bridge pattern?
    • The Bridge pattern separates an abstraction from its implementation, allowing them to vary independently.
  4. Q: What is the Composite pattern?
    • The Composite pattern allows you to compose objects into tree structures to represent part-whole hierarchies.
  5. Q: What is the Decorator pattern?
    • The Decorator pattern adds new functionality to an object dynamically without altering its structure.
  6. Q: What is the Facade pattern?
    • The Facade pattern provides a simplified interface to a larger body of code, making it easier to use.
  7. Q: What is the Flyweight pattern?
    • The Flyweight pattern reduces memory usage by sharing as much data as possible with similar objects.
  8. Q: What is the Proxy pattern?
    • The Proxy pattern provides a surrogate or placeholder for another object to control access to it.
  9. Q: When should you use the Adapter pattern?
    • Use the Adapter pattern when you need to integrate a class with an incompatible interface into your application.
  10. Q: What are the benefits of the Composite pattern?
    • It simplifies client code by treating individual objects and compositions of objects uniformly.

Behavioral Design Patterns

  1. Q: What are behavioral design patterns?
    • Behavioral patterns deal with communication between objects and how they interact.
  2. Q: What is the Chain of Responsibility pattern?
    • The Chain of Responsibility pattern passes a request along a chain of handlers until one of them handles it.
  3. Q: What is the Command pattern?
    • The Command pattern encapsulates a request as an object, allowing you to parameterize clients with different requests.
  4. Q: What is the Interpreter pattern?
    • The Interpreter pattern defines a representation for a language’s grammar and provides an interpreter to evaluate sentences in the language.
  5. Q: What is the Iterator pattern?
    • The Iterator pattern provides a way to access elements of a collection sequentially without exposing its underlying representation.
  6. Q: What is the Mediator pattern?
    • The Mediator pattern defines an object that encapsulates how a set of objects interact, promoting loose coupling.
  7. Q: What is the Memento pattern?
    • The Memento pattern captures and restores an object’s internal state without violating encapsulation.
  8. Q: What is the Observer pattern?
    • The Observer pattern defines a one-to-many dependency between objects so that when one object changes state, all its dependents are notified.
  9. Q: What is the State pattern?
    • The State pattern allows an object to alter its behavior when its internal state changes.
  10. Q: What is the Strategy pattern?
    • The Strategy pattern defines a family of algorithms, encapsulates each one, and makes them interchangeable.
  11. Q: What is the Template Method pattern?
    • The Template Method pattern defines the skeleton of an algorithm in a method, deferring some steps to subclasses.
  12. Q: What is the Visitor pattern?
    • The Visitor pattern separates an algorithm from the object structure it operates on, allowing you to add new operations without modifying the objects.
  13. Q: When should you use the Observer pattern?
    • Use the Observer pattern when changes to one object need to be reflected in other objects.
  14. Q: What are the advantages of the Strategy pattern?
    • It promotes the Open/Closed Principle by allowing new algorithms to be added without modifying existing code.
  15. Q: What are the drawbacks of the Mediator pattern?
    • It can become a bottleneck if the mediator grows too complex.

Advanced Questions

  1. Q: How do design patterns promote the SOLID principles?
    • Design patterns like Singleton, Factory, and Strategy align with SOLID principles by promoting single responsibility, open/closed design, and dependency inversion.
  2. Q: Can design patterns be combined?
    • Yes, design patterns can be combined to solve complex problems. For example, the Factory Method can be used with the Singleton pattern.
  3. Q: What is anti-pattern?
    • An anti-pattern is a common but ineffective or counterproductive solution to a recurring problem.
  4. Q: How do you choose the right design pattern?
    • Analyze the problem, consider the context, and choose a pattern that best fits the requirements.
  5. Q: Are design patterns language-specific?
    • No, design patterns are not tied to any specific programming language and can be implemented in any language.