Design Patterns

Question 1

Creational

Answer 1

Class instantiation or object creation
Abstract factory
Builder
Method
Prototype
Singleton

Question 2

Structural

Answer 2

Organizing different classes and objects to form larger structures that provide new functionality
Relationship between objects
Adapter
Bridge
Composite
Decorator
Facade
Flyweight
Proxy

Question 3

Abstract factory

Answer 3

Creational pattern

Produce families of related objects without concrete classes

Question 4

Builder

Answer 4

Creational pattern

build a complex object using simple objects and step by step approach

Question 5

Method

Answer 5

Creational pattern
provides interface for creating objects in a super class but allow subclass to alter type of object created.

Question 6

Prototype

Answer 6

Clone existing object/clone new instance from prototype

Question 7

Singletone

Answer 7

Creational pattern
Ensure only one instance of the class and provide a global access point to this instance

Question 8

Adapter

Answer 8

Structural Pattern

Allow objects with different interfaces to collaborate

Question 9

Bridge

Answer 9

Structural Pattern

Question 10

Composite

Answer 10

Structural Pattern

Compose objects into tree structure, treat this group of objects similar way to a single object

Question 11

Decorator

Answer 11

Structural Pattern
Add new functionality to objects by wrapping it in a decorator class with the new behaviours

Question 12

Facade

Answer 12

Structural Pattern

provides a simple interface to hide complexity of existing system

Question 13

Flyweight

Answer 13

Structural Pattern

Fit more objects into available amount of RAM by sharing common parts of state between multiple objects

Question 14

Proxy

Answer 14

Structural Pattern

Question 15

Behaviour Design Pattern

Answer 15

Communication or interaction between objects

Question 16

Chain Of Responsibility

Answer 16

pass requests along a chain of handlers, each handler decides to process request or pass it to next handler in chain

Question 17

Command

Answer 17

object used to encapsulate all information needed to perform action or trigger an event at later time

Question 18

Iterator

Answer 18

aggregate and access elements sequentially without exposing its underlying representation

Question 19

Interpreter

Answer 19

Language interpreter for a small grammar

Question 20

Mediator

Answer 20

restricts direct communication between objects/classes instead uses a mediator object

Question 21

Memento

Answer 21

Restore state of object to previous state

Question 22

Observer

Answer 22

used in one to many relationships between objects. When one is modified the dependent objects are automatically notified

Question 23

State

Answer 23

lets an object alter its behaviour when its internal state changes

Question 24

Strategy

Answer 24

selecting algorithm at runtime depending on context object as oppose to having one algorithm, e.g. diff transport modes in nav app

Question 25

Template Method

Answer 25

Algorithm with some steps supplied by a derived class

Question 26

Visitor

Answer 26

operations applied to elements of a heterogeneous object structure