Design Pattern

Question 1

Abstract Factory

Answer 1

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

Question 2

Adapter

Answer 2

Convert the interface of a class into another interface clients expect

Question 3

Bridge

Answer 3

Decouple an abstraction from an implementation so the two can vary independently

Question 4

Builder

Answer 4

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

Question 5

Chain of Responsibility

Answer 5

Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request

Question 6

Command

Answer 6

Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations

Question 7

Composite

Answer 7

Compose objects into tree structures to represent part-whole hierarchies

Question 8

Decorator

Answer 8

Attach additional responsibilities to an object dynamically

Question 9

Facade

Answer 9

Provide a unified interface to a set of interfaces in a subsystem

Question 10

Factory Method

Answer 10

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

Question 11

Flyweight

Answer 11

Use sharing to support large numbers of fine-grained objects efficiently

Question 12

Interpreter

Answer 12

Given a language, define a representation for its grammar along with an interpreter that uses the representation to interpret sentences in the language

Question 13

Iterator

Answer 13

Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation

Question 14

Mediator

Answer 14

Define an object that encapsulates how a set of objects interact

Question 15

Memento

Answer 15

Without violating encapsulation, capture and externalize an objects internal state so that the object can be resored to this state later

Question 16

Observer

Answer 16

Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically

Question 17

Prototype

Answer 17

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

Question 18

Proxy

Answer 18

Provide a surrogate or placeholder for another object to control access to it

Question 19

Singleton

Answer 19

Ensure a class only has one instance, and provide a global point of access to it

Question 20

State

Answer 20

Allow an object to alter its behaviour when its internal state changes

Question 21

Strategy

Answer 21

Define a family of algorithms, encapsulate each one, and make them interchangeable

Question 22

Template Method

Answer 22

Define the skeleton of an algorithm in an operation, deferring some steps to subclasses

Question 23

Visitor

Answer 23

Represent an operation to be performed on the elements of an object structure