Patterns

Question 1

Factory

Answer 1

Creational pattern.

Creates objects based on some input data.

Question 2

Abstract Factory

Answer 2

Creational pattern.

Creates factories based on some input data.

Question 3

Singleton

Answer 3

Creational pattern.

Object with a single instance, available via static method.

Question 4

Builder

Answer 4

Creational pattern.
Builds complex item in steps with builder class and helper methods.

Question 5

Prototype

Answer 5

Creational pattern.

Object is created by cloning existing object (to avoid requesting data if it is costly).

Question 6

Adapter / Wrapper

Answer 6

Structural pattern.

Object is put inside other object and its methods mapped to the required methods.

Question 7

Bridge

Answer 7

Structural pattern.

Multiple classes implement same interface, acting thus as bridge to different realisations.

Question 8

Filter (Criteria)

Answer 8

Structural pattern.

Object that filters some data and can be combined with objects which filter the same type of data.

Question 9

Composite

Answer 9

Structural pattern.

Used when we need to treat heirarchy of objects as one object.

Question 10

Decorator

Answer 10

Structural pattern.

Allows for the dynamic wrapping of objects in order to modify their existing responsibilities and behaviors.

Question 11

Facade

Answer 11

Structural pattern.

Hides complexity of some code behind simplified interface.

Question 12

Flyweight

Answer 12

Structural pattern.

Reusing existing objects as much as possible to lower memory footprint.

Question 13

Proxy

Answer 13

Structural pattern.

Controls and manages access to some other object.

Question 14

Chain of responsibility

Answer 14

Behavioral pattern.

Gives more than one object an opportunity to handle a request by linking receiving objects together.

Question 15

Command

Answer 15

Behavioral pattern.

Command is sent in a form of object to the other object which can execute it.

Question 16

Interpreter

Answer 16

Behavioral pattern.

Describes how one type of data should be converted to some other related type.

Question 17

Iterator

Answer 17

Behavioral pattern.

Provides access to the collection without any need to know underlying implementation.

Question 18

Mediator

Answer 18

Behavioral pattern.

Object acts as a central hub which manages communication of a group of objects.

Question 19

Memento

Answer 19

Behavioral pattern.

Saving state of an object externally to be restored later.

Question 20

Observer

Answer 20

Behavioral pattern.

Observable object provides ways for Observers to subscribe to data it emits.

Question 21

State

Answer 21

Behavioral pattern.

Behaviour of an object depends on its state.

Question 22

Null

Answer 22

Behavioral pattern.

Special object which reflects a do nothing relationship.

Question 23

Strategy

Answer 23

Behavioral pattern.

When object changes its behavior depending on external circumstances.

Question 24

Template

Answer 24

Behavioral pattern.
Subclasses override methods from class to provide different behaviours.

Question 25

Visitor

Answer 25

Behavioral pattern.

Group of objects accept visitor object which describes some logic operations using them, thus externalizing logic.

Question 26

Factory method

Answer 26

Creational pattern.

Provides a method to create an instance of the class.

Question 27

Dependency injection

Answer 27

Creational pattern.

Class does not create classes it needs for working recieving them from outside instead.

Question 28

Lazy initiation

Answer 28

Creational pattern.

Object is only initiated when it is actually needed.

Question 29

Multiton

Answer 29

Creational pattern.
Ensures class has only named instances and provides global point of access to get them.

Question 30

Object pool

Answer 30

Creational pattern.

Avoid expensive aquisition and release of resources by recycling objects which are no longer in use.