Week 5: Frameworks and Pattern Introduction

Question 1

What is a framework?

Answer 1

A reusable skeleton of an application that can be customised and used by a developer to be the backbone for different applications.

Question 2

What are the two types of Frameworks?

Answer 2

Black box and White box.

Question 3

What is a black box framework?

Answer 3

A framework where it is parameterised and the application using it has little to no interaction with the actual framework source code.

These are designed with end users in mind.

Question 4

What is a white box framework?

Answer 4

A framework that is reusable as the design of all or part of a system that is represented as a set of abstract classes and the way their instance interact.

Question 5

What is a white box framework?

Answer 5

A framework that is reusable as the design of all or part of a system that is represented as a set of abstract classes and the way their instance interact.

Question 6

What is the JHotDraw framework?

Answer 6

A framework for creating ‘semantic’ drawing editors. It provides tools for creating shapes, drawings, constrained connections between objects on screen and limited animation

Question 7

What is the typical kind of program that might use the JHotDraw framework?

Answer 7

A UML diagram creation program.

Question 8

What kind of architecture design does JHotDraw follow?

Answer 8

Model View Controller (MVC)

Question 9

Explain the class that represents the Model in JHotDraw.

Answer 9

The drawing class
It's a container for the figure models. It listens for any figure changes on the View and updates the data. This is done via the observer design pattern.

Question 10

Explain the class that represents the View in JHotDraw.

Answer 10

The DrawingView class.

It is responsible for creating and displaying the GUI. It makes use of the observer design pattern.

Question 11

Explain the class that represents the Controller in JHotDraw.

Answer 11

The DrawingEditor class.
New applications that want to use JHotDraw should extend this controller. It is the backbone of JHD, including all its core functionality. It makes use of the factory method design pattern.

Question 12

Explain the Figure class in JHotDraw.

Answer 12

It is a key class/interface of the framework. Every model that can be manipulated and drawn within JHD inherits from Figure, whether directly or indirectly.
Figures can be drawn/manipulated within the rectualer DisplayBox in the View.

Question 13

Name and explain three things in JHotDraw that are associated with and can manipulate figures.

Answer 13

1. Handles - can be used to effect the properties of figures e.g. Stretch, move, resize etc.
2. Connectors - used to join figures together by their connection points (Connection points are points on figures that can be used to connect to other figures via a line or arrow etc.)
3. Locators - used to locate points on a figure to position the handles (e.g. North East corner point)

Question 14

What design pattern do both connectors and locators use?

Answer 14

Strategy design pattern.

Question 15

What is the Painter in JHotDraw?

Answer 15

An algorithm used for drawing on screen.

It uses the strategy design pattern.

Question 16

What are the Tools in JHotDraw?

Answer 16

It’s a panel that goes down the left hand side. It shows all the tools that can be used in the application. New applications can create their own tools for JHotDraw. Creating new tools uses the prototype design pattern.

Question 17

What design pattern is used when switching between tools in JHotDraw?

Answer 17

The state design pattern.

Question 18

Explain the Command in terms of JHotDraw.

Answer 18

It is used to encapsulate an action to be executed. It uses the command design pattern.

Question 19

Explain what PointConstrainer does in JHotDraw.

Answer 19

It is used to contrain points in the application view, like snapping figures to a grid layout.

Question 20

What is LineConnection in JHotDraw?

Answer 20

The on screen visual connection between figures. Normally resented by a line. It implements ConnectionFigure and is classed as a figure model itself. It uses the observer design pattern to listen for changes in the figures it is connected to.

Question 21

What makes Frameworks so flexible and reusable?

Answer 21

The use of Interfaces and Abstract classes.

Question 22

What is an interface?

Answer 22

A type that cannot ever be created as an instanced object. It has a name and a set of methods, which an not implemented. The can provide the backbone for classes that implement said interface.

Question 23

Name a couple fo interfaces used in JHotDraw.

Answer 23

Drawing
Figure
Connector
Handle
DrawingView
Painter
Etc.

Question 24

TRUE or FALSE: A class can implement many interfaces at once.

Answer 24

True

Question 25

TRUE or FALSE: A class can only extend one other class?

Answer 25

True

Question 26

TRUE or FALSE: A class can only extend one other class?

Answer 26

True

Question 27

What are abstract classes?

Answer 27

A class that has implemented/coded methods and variables, yet it still cannot be created as an instance variable.
Nornally used to be a superclass of many similar subclasses to provide shared functionality, or to flesh out interfaces by giving some concrete functionality.

Question 28

What is an abstract method?

Answer 28

A method that can be created in an abstract class that has no implementation in that class. Similar to methods in interfaces.

They are created using the method tag abstract, for example:

public abstract void MethodName(Parameters);

Question 29

What abstract class directly implements figure?

Answer 29

AttributeFigure.

Question 30

What is a design pattern?

Answer 30

A named pattern that that can provide the template to create a solution for a recurring problem within a certain context.
They may need to be adapted to solve different problems.

Question 31

Why are design patterns good?

Answer 31

Reuse - Their solution can be reused in many solutions.
Design communication - Provides a way to communicate about the architecture of software, makes it more standardised and descriptive.

Question 32

Where did design patterns come from?

Answer 32

Originated in building architecture with a man named Christopher Alexander. He noticed common patterns in the architecture of buildings that solved problems. He wrote a book on this describing these patterns, designs and practices. It was then later adapted for computing architecture.

Question 33

What was the first design pattern computing publication?

Answer 33

Design Patterns, by Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides.

Question 34

What are the 3 main classifications for design patterns?

Answer 34

Creatiobal
Structural
Behavioural

Question 35

How are deidgn patterns described? What properties and fields?

Answer 35

BASE INFO
Pattern name
Pattern classification
Intent - The problem addressed
Motivation - example 
Applicability - situations used/poor designs

DETAILS OF THE PATTERNS
Structure
Participants
Collaborations

Consequences - trade offs of pattern
Implementation - how to implement
Sample code - shows for only a particular instance/problem
Known uses
Realted patterns

Question 36

Name some patterns in the creational classification.

Answer 36

Factory Method

Prototype

Question 37

Name some patterns in the structural classification.

Answer 37

Adapter

Composite

Question 38

Name some patterns in the behavioural classification.

Answer 38

Template Method
Observer
State
Strategy