Quiz

# Design patterns quiz

1) You need one and only one database connection pool, lazily initialised, thread-safe.
   a) Singleton  b) Factory  c) Prototype  d) Builder

2) Construct complex objects step by step with optional fields, immutable result.
   a) Factory  b) Builder  c) Strategy  d) Adapter

3) Swap a sort algorithm at runtime without touching the caller.
   a) Strategy  b) Template Method  c) Decorator  d) State

4) Wrap an incompatible third-party API so your code can keep its own interface.
   a) Adapter  b) Facade  c) Proxy  d) Bridge

5) Add behaviour to an object dynamically without subclassing.
   a) Decorator  b) Composite  c) Visitor  d) Memento

6) One-to-many notification when state changes - and the publishers should not know subscribers.
   a) Observer  b) Mediator  c) Chain of Responsibility  d) Command

7) Encapsulate a request so it can be queued, logged, or undone.
   a) Command  b) State  c) Memento  d) Iterator

8) Walk a tree-shaped structure and perform different operations per node type.
   a) Visitor  b) Iterator  c) Composite  d) Template Method

Answers: 1a, 2b, 3a, 4a, 5a, 6a, 7a, 8a.

When you miss one, ask: what problem does that pattern actually solve? Patterns are vocabulary, not boilerplate.

// 3 questions per lesson.