Design Patterns

Question 1

Provides an interface for creating objects in a superclass, but allows subclasses to alter the type of objects that will be created.

Answer 1

Factory Method

Question 2

Lets you produce families of related objects without specifying their concrete classes.

Answer 2

Abstract Factory

Question 3

Lets you construct complex objects step by step. The pattern allows you to produce different types and representations of an object using the same construction code.

Answer 3

Builder

Question 4

Lets you copy existing objects without making your code dependent on their classes.

Answer 4

Prototype

Question 5

Lets you ensure that a class has only one instance, while providing a global access point to this instance.

Answer 5

Singleton

Question 6

Allows objects with incompatible interfaces to collaborate.

Answer 6

Adapter

Question 7

Lets you compose objects into tree structures and then work with these structures as if they were individual objects.

Answer 7

Composite

Question 8

Provides a simplified interface to a library, a framework, or any other complex set of classes.

Answer 8

Facade

Question 9

Lets you split a large class or a set of closely related classes into two separate hierarchies—abstraction and implementation—which can be developed independently of each other.

Answer 9

Bridge

Question 10

Lets you attach new behaviors to objects by placing these objects inside special wrapper objects that contain the behaviors.

Answer 10

Decorator

Question 11

Lets you fit more objects into the available amount of RAM by sharing common parts of state between multiple objects instead of keeping all of the data in each object.

Answer 11

Flyweight

Question 12

Lets you provide a substitute or placeholder for another object. It controls access to the original object, allowing you to perform something either before or after the request gets through to the original object.

Answer 12

Proxy

Question 13

Lets you pass requests along a chain of handlers. Upon receiving a request, each handler decides either to process the request or to pass it to the next handler in the chain.

Answer 13

Chain of Responsibility

Question 14

Lets you traverse elements of a collection without exposing its underlying representation (list, stack, tree, etc.).

Answer 14

Iterator

Question 15

Lets you save and restore the previous state of an object without revealing the details of its implementation.

Answer 15

Memento

Question 16

Lets an object alter its behavior when its internal state changes. It appears as if the object changed its class.

Answer 16

State

Question 17

Defines the skeleton of an algorithm in the superclass but lets subclasses override specific steps of the algorithm without changing its structure.

Answer 17

Template Method

Question 18

Lets you separate algorithms from the objects on which they operate.

Answer 18

Visitor

Question 19

Lets you define a family of algorithms, put each of them into a separate class, and make their objects interchangeable.

Answer 19

Strategy

Question 20

Lets you define a subscription mechanism to notify multiple objects about any events that happen to the object they’re observing.

Answer 20

Observer

Question 21

Lets you reduce chaotic dependencies between objects. The pattern restricts direct communications between the objects and forces them to collaborate.

Answer 21

Mediator

Question 22

Turns a request into a stand-alone object that contains all information about the request. This transformation lets you parameterize methods with different requests, delay or queue a request’s execution, and support undoable operations.

Answer 22

Command