Design Patterns

Question 1

What do Creational patterns deal with?

Answer 1

How an object is created

Question 2

What are the two basic ideas behind creational design patterns?

Answer 2

1. Encapsulating the knowledge of which concrete types should be created
2. Hiding how the instances of these types are created

Question 3

List five well-known patterns that are part of the creational pattern category.

Answer 3

1. The abstract factory pattern
2. The builder pattern
3. The factory method pattern
4. The prototype pattern
5. The singleton pattern

Question 4

What does the abstract factory pattern do?

Answer 4

Provides an interface for creating related objects without specifying the concrete type

Question 5

What does the builder pattern do?

Answer 5

Separates the construction of a complex object from its representation, so the same process can be used to create similar types.

Question 6

What does the factory method pattern do?

Answer 6

Creates objects without exposing the underlying logic of how the object (or which type of object) is created.

Question 7

What does the prototype pattern do?

Answer 7

Creates an object by cloning an existing one.

Question 8

What does the singleton pattern do?

Answer 8

Allows one (and only one) instance of a class for the lifetime of an application.

Question 9

What are structural patterns?

Answer 9

Structural patterns concern types and object compositions

Question 10

What do behavioural patterns do?

Answer 10

Communicate between types.

Question 11

What do structural design patterns describe?

Answer 11

How types can be combined to form larger structures.

Question 12

List seven well-known patterns that are part of the structural design pattern type?

Answer 12

1. Adapter
2. Bridge
3. Composite
4. Decorator
5. Facade
6. Flyweight
7. Proxy

Question 13

What does the adapter pattern do?

Answer 13

Allows types with incompatible interfaces to work together

Question 14

What is the bridge pattern used for?

Answer 14

To separate the abstract elements of a type from the implementation so the two can vary.

Question 15

What does the composite pattern do?

Answer 15

Allows the application to treat a group of objects as a single object.

Question 16

What does the decorator pattern do?

Answer 16

Lets us add or override behavior in an existing method of an object.

Question 17

What does the facade pattern do?

Answer 17

It provides a simplified interface for a larger and more complex body of code.

Question 18

What does the flyweight pattern do?

Answer 18

It allows us to reduce the resources needed to create and use a large number of similar objects.

Question 19

What is the proxy pattern?

Answer 19

This is a type acting as an interface for another class or classes.

Question 20

What do behavioral design patterns do?

Answer 20

They explain how types interact with each other.

Question 21

List 9 well-known patterns that are part of the behavioral design pattern type

Answer 21

1. Chain of responsibility
2. Command
3. Iterator
4. Mediator
5. Memento
6. Observer
7. State
8. Strategy
9. Visitor

Question 22

What is the chain of responsibility design pattern used for?

Answer 22

To process a variety of requests, each of which may be delegated to a different handler

Question 23

What does the command design pattern do?

Answer 23

Creates objects that can encapsulate actions or parameters so that they can be invoked later or by a different component.

Question 24

What does the iterator design pattern do?

Answer 24

Allows us to access the elements of an object sequentially without exposing the underlying structure.

Question 25

What is the mediator design pattern used for?

Answer 25

To reduce coupling between types that communicate with each other.

Question 26

What is the memento design pattern used for?

Answer 26

To capture the current state of an object and store it in a manner that an be restored later.

Question 27

What does the observer design pattern do?

Answer 27

It allows an object to publish changes to an object’s state. Other objects can then subscribe so they can be notified of any changes.

Question 28

What is the state design pattern used to do?

Answer 28

To alter the behavior of an object when its internal state changes.

Question 29

What does the strategy design pattern do?

Answer 29

It allows one out of a family of algorithms to be chosen at runtime.

Question 30

What is the visitor design pattern?

Answer 30

This is a way of separating an algorithm from an object structure.