Catalog

Question 1

Abstract Factory

Answer 1

Provide 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. Lets classes work together that couldn’t otherwise because of incompatible interfaces.

Question 3

Bridge

Answer 3

Decouple an abstraction from its implementation so that 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. Chain the receiving objects and pass the request along the chain until an object handles it.

Question 6

Command

Answer 6

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

Question 7

Decorator

Answer 7

Attach additional responsibilities to an object dynamically. Provide a flexible alternative to subclassing for extending functionality.

Question 8

Facade

Answer 8

Provide a unified interface to a set of interfaces in a subsystem. Defines a higher-level interface that makes the subsystem easier to use.

Question 9

Factory Method

Answer 9

Define an interface for creating an object, but let subclasses decide which class to instantiate. Lets a class defer instantiation to subclasses.

Question 10

Flyweight

Answer 10

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

Question 11

Interpreter

Answer 11

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

Question 12

Iterator

Answer 12

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

Question 13

Mediator

Answer 13

Define an object that encapsulates how a set of objects interact. Promotes loose coupling by keeping objects from referring to each other explicitly, and lets you vary their interaction independently.

Question 14

Memento

Answer 14

Without violating encapsulation, capture and internalize an object’s internal state so that the objct can be restored to that state later.

Question 15

Observer

Answer 15

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

Question 16

Prototype

Answer 16

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

Question 17

Proxy

Answer 17

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

Question 18

Singleton

Answer 18

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

Question 19

State

Answer 19

Allow an object to alter its behavior when its internal state changes. The object will appear to change its class.

Question 20

Strategy

Answer 20

Define a family of algorithms, encapsulate each one, and make them interchangeable. Lets the algorithm vary independently from clients that use it.

Question 21

Template Method

Answer 21

Define the skeleton of an algorithm in an operation, deferring some steps to subclasses. Lets subclasses redefine certain steps of an algorithm without changing the algorithm’s structure.

Question 22

Visitor

Answer 22

Represent an operation to be performed on the elements of an object structure. Lets you define a new operation without changing the classes of the elements on which it operates.