Gof

Question 1

Which pattern restricts the initialization of a class to ensure that only one instance of the class can be created?

Answer 1

Singleton

Question 2

Which pattern takes out the responsibility of instantiating a object from the class to a new class with only this responsibility?

Answer 2

Factory

Question 3

Which pattern create a Factory for factory classes?

Answer 3

Abstract Factory

Question 4

Which creates an object step by step and a method to finally get the object instance?

Answer 4

Builder

Question 5

Which pattern creates a new object instance from another similar instance and then modify according to our requirements?

Answer 5

Prototype

Question 6

Which pattern creates an interface so that two distinct interfaces can work together?

Answer 6

Adapter

Question 7

Which pattern creates an interface with multiple pieces or leaves in a part-whole?

Answer 7

Composite (FileSystemItem -> File, Directory that contains files)

Question 8

Which pattern creates a new object that controls an object?

Answer 8

Proxy (Functionality -> AdminFunctionality)

Question 9

Which pattern caches objects so that they do not need to be instantiated again for the same functionality?

Answer 9

Flyweight

Question 10

Which pattern creates an interface so that it lowers complexity of its parts?

Answer 10

Facade (SoundSystem, TvSystem -> HomeTheaterFacade)

Question 11

Which pattern creates an abstraction so that both implementations and interfaces can grow separately?

Answer 11

Bridge
abstract vehicle - bus,bike
interface WorkShop - produce, assemble)

Question 12

Which pattern creates an abstract class that defines the skeleton and passes the responsibility of implementing some steps to the subclasses?

Answer 12

Template
(Abstract BuildHouse -> GlassHouse, WoodenHouse)

Question 13

Which pattern abstract communications between objects, decoupling them into a single interface?

Answer 13

Mediator

Question 14

Which pattern decouples client requests that follow a order so that each step is not coupled?

Answer 14

Chain of responsibility
(ATM dispenser with 50DollarDispense, 20DollarDispense, etc)

Question 15

Which pattern makes objects be notified of changes made to their interested objects?

Answer 15

Observer
interface Observer -> class YtSubscriber
interface Subject -> class YtChannel

Question 16

Which pattern enables multiple implementations to be selected at runtime?

Answer 16

Strategy
interface PaymentStrategy -> CreditCard, Cash

Question 17

Which pattern decouples the sender of the request from the receiver?

Answer 17

Command
interface Command -> class TurnLightOnCommand

Question 18

Which pattern decouples if-else implentations to be applyed when the object internal memory is changed?

Answer 18

State
interface TvState -> OnState, OffState
doAction now would do different things depending on the internal state

Question 19

Which pattern decouples implementations from classes that are similar, without ever changing the original classes?

Answer 19

Visitor
interface FruitColorVisitor
visitBanana
visitApple
interface FruitPriceVisitor
visitBanana
visitApple

Question 20

Which defines a grammatical representation for a language and provides an interpreter to deal with this grammar?

Answer 20

Interpreter
Calculator example

Question 21

Which pattern allows us to recover previous states of an object so that it can be restored?

Answer 21

Memento
classic undo redo

Question 21

Which pattern decouples how we trasverse through objects of multiple collections while having types of collections?

Answer 21

Iterator

Question 22

Which pattern is used to modify the functionality of an object at runtime?

Answer 22

Decorator
interface Coffee
CoffeeLatteDecorator implements Coffee