Design Pattern Design Patterns Syllabus

Design Patterns syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Design Patterns in Design Pattern, not a summary of it.

1. 1

   Creational Patterns

   5 topics

   • Singleton
   • Factory Method
   • Abstract Factory
   • Builder
   • Prototype
2. 2

   Structural Patterns

   7 topics

   • Adapter
   • Bridge
   • Composite
   • Decorator
   • Facade
   • Flyweight
   • Proxy
3. 3

   Behavioral Patterns

   11 topics

   • Chain of Responsibility
   • Command
   • Interpreter
   • Iterator
   • Mediator
   • Memento
   • Observer
   • State
   • Strategy
   • Template Method
   • Visitor
4. 4

   Concurrency Patterns

   8 topics

   • Active Object
   • Monitor Object
   • Scheduler
   • Thread Pool
   • Read-Write Lock
   • Producer-Consumer
   • Reactor
   • Balking
5. 5

   Architectural Patterns

   8 topics

   • MVC (Model-View-Controller)
   • MVVM (Model-View-ViewModel)
   • Microservices
   • Layered Architecture
   • Event-Driven Architecture
   • Service-Oriented Architecture
   • Hexagonal Architecture
   • CQRS (Command Query Responsibility Segregation)

Design Patterns flashcards for Design Pattern

23 of 51 cards from the Design Patterns deck — real questions with worked answers.

1. Into which three families does the classic Gang of Four (GoF) taxonomy classify design patterns?

   Creational, Structural, and Behavioral patterns.

2. Classify each of these as Creational, Structural, or Behavioral: Singleton, Adapter, Command.

   Singleton = Creational; Adapter = Structural; Command = Behavioral.

3. What is the intent of the Singleton pattern?

   Ensure a class has only one instance and provide a global point of access to that instance.

4. Name two common techniques used to make a Singleton thread-safe in a lazy-initialization scenario.

   Double-checked locking (with a volatile field) and the initialization-on-demand holder idiom (static inner holder class); an eager static instance also avoids the race entirely.

5. Why is a private constructor essential to the Singleton pattern?

   It prevents any external code from instantiating the class with 'new', forcing all access through the controlled static accessor that returns the sole instance.

6. What is the intent of the Factory Method pattern?

   Define an interface for creating an object, but let subclasses decide which class to instantiate, deferring instantiation to subclasses.

7. In Factory Method, what are the four participant roles?

   Product (interface), ConcreteProduct, Creator (declares the factory method), and ConcreteCreator (overrides the factory method to return a ConcreteProduct).

8. What is the intent of the Abstract Factory pattern?

   Provide an interface for creating families of related or dependent objects without specifying their concrete classes.

9. How does Abstract Factory differ from Factory Method?

   Factory Method uses inheritance and a single method to create one product; Abstract Factory uses composition (an object) to create whole families of related products, typically via multiple factory methods.

10. What is the intent of the Builder pattern?

    Separate the construction of a complex object from its representation so that the same construction process can create different representations.

11. Name the four participants of the Builder pattern.

    Builder (abstract interface), ConcreteBuilder, Director (controls the construction sequence), and Product.

12. When is Builder preferred over a telescoping constructor?

    When an object has many optional parameters or requires a step-by-step construction process, Builder avoids constructors with long confusing parameter lists and produces immutable, validated objects.

13. What is the intent of the Prototype pattern?

    Specify the kinds of objects to create using a prototypical instance, and create new objects by copying (cloning) this prototype.

14. What is the difference between a shallow copy and a deep copy in the context of Prototype?

    A shallow copy duplicates the object's fields but shares referenced sub-objects; a deep copy recursively clones referenced sub-objects so the clone is fully independent.

15. Which creational pattern is most useful when object creation is costly and you want to avoid building from scratch?

    Prototype, which creates new objects by cloning an existing configured instance rather than re-initializing from scratch.

16. What is the intent of the Adapter pattern?

    Convert the interface of a class into another interface that clients expect, letting classes work together that otherwise couldn't due to incompatible interfaces.

17. What is the difference between a class adapter and an object adapter?

    A class adapter uses multiple inheritance to adapt one interface to another; an object adapter uses composition, holding an instance of the adaptee and delegating calls to it.

18. What is the intent of the Bridge pattern?

    Decouple an abstraction from its implementation so that the two can vary independently.

19. How does Bridge avoid a combinatorial explosion of subclasses?

    By splitting the hierarchy into two independent dimensions (abstraction and implementation) joined by composition, so m abstractions and n implementations need m + n classes instead of m × n.

20. What is the key structural difference between Adapter and Bridge?

    Adapter is applied after the fact to make unrelated existing interfaces work together; Bridge is designed up front to let abstraction and implementation vary independently.

21. What is the intent of the Composite pattern?

    Compose objects into tree structures to represent part-whole hierarchies, letting clients treat individual objects and compositions of objects uniformly.

22. Name the three participant roles in the Composite pattern.

    Component (common interface), Leaf (no children), and Composite (has children and implements child-management operations).

23. What is the intent of the Decorator pattern?

    Attach additional responsibilities to an object dynamically, providing a flexible alternative to subclassing for extending functionality.

See more Design Patterns flashcards →

Planning Design Patterns for Design Pattern

Design Patterns (Design Pattern) FAQ