Design Patterns (Kees Van Heuven)

Front 1

Design principle #1

Back 1

Identify the aspects of your code that vary and seperate them from what stays the same.

Front 2

Noem enkele Desing Patterns

Back 2

Strategy pattern
Observer pattern
Decorator pattern
Singleton pattern
State pattern
Collection pattern

Front 3

Encapsulate what varies?

Back 3

If some aspect of code is changing.
By seperating out the parts of your code that vary.

Front 4

Design principle #2

Back 4

Program against a interface.

Front 5

Design principle #3

Back 5

Favor composition over inheritance.

Front 6

Design principle #4

Back 6

Strive for loosely coupled designs between objects that interact.

Front 7

Design principle #5

Back 7

Classes should be open for extension but closed for modification.

Front 8

Explain the open-closed principal.
One of the most important design principles.

Back 8

We want classes to be open to extensions of behaviour.
But we also want classes closed to modifcation.
Our goal is to be able to easily augment what we have but without modifying existing code.

Front 9

Decorator Pattern

Back 9

Attached additional responsibilities to an object dynamically.
Decorators provide a flexible alternative to subclassing for extending functionality.

Front 10

Singleton Pattern

Back 10

Ensures a class has only one instance and provide a global access point to it.

Front 11

Why Singleton pattern?

Back 11

Connection and thread pools
Logging facilities
Preference and registry objects
Device, printer, and graphics drivers
Anywhere you want to ensure a resource exists only once.

Front 12

Hoe ziet een Singleton Class Diagram eruit?

Back 12

Class= Singleton
static Single instance= static uniqueInstance
static method= static getInstance()

Front 13

What is Lazy Instanciation?

Back 13

It insurces that only one instance of a class will ever excist.
If no object in the code ever calls tne instance method, it will never be instanciated.

Front 14

In wich situation the Singleton pattern fails?

Back 14

In a multi thread situation

Front 15

Wich two ways make the Singleton pattern "thread safe"?

Back 15

Create a instance "needy instead of lazy", it will be always created.
Add the keyword synchronized to the getInstance method.

Front 16

The Observer pattern bestaat uit 2 objecten, welke zijn dit?

Back 16

Publishers
Subscibers

Front 17

Beschrijf het Observer Pattern.

Back 17

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

Front 18

Wat zijn de objecten in een one-to-many relationship?

Back 18

Subject
Dependent

Front 19

Hoe ziet het class diagram van een Subject eruit?

Back 19

interface name= Subject
method= registerObserver()
method= removeObserver()
method= notifyObserver()

Front 20

Uit welke patterns bestaat het MVC pattern?

Back 20

1.Observer pattern
2.
3.

Front 21

Op vlo staat een docuement met de aliase en de omschrijvingen vand e besproken patterns

Back 21

check vlo allPatterns.docx