Object Oriented Analysisand

Object Oriented Programming

Session 4

LBSC 790 / INFM 718B

Building the Human-Computer Interface

Agenda

• Class diagrams

• Object diagrams

• Object design

• Object oriented programming in Java

Object Modeling

• Models are abstractions of reality– That are created for a specific purpose

• Classes represent types of entities– That are important for the chosen purpose– Specify subordinate objects and methods

• Objects are specific instances of classes– Encapsulate specific objects and methods

Flight Finder Exercise

http://www.glue.umd.edu/~oard/spacea/ff/

Flight Finder Background• The traveler (or a system administrator) will first obtain schedule data

from JOSAC using their Web browser and store it on their hard drive in the received format. Upon program initiation, the Parse Sched use case will run automatically. Once that completes, the traveler may specify the origin, destination, radius around each, and a connection radius (or leave any of the default values set), earliest and latest times, and then initiate the search. Once the search completes, the traveler may step through the interesting routes one at a time, viewing information on which their decision might be based. Once one or more acceptable routes have been identified, the traveler can then contact the appropriate facilities directly to make travel arrangements.

FlightFinder Use Case Diagram

JOSAC

Traveler

Select

Search

ParseSched

<<include>>

<<include>>

Search Use Case Narrative• Assumptions

– Current JOSAC schedule parsed

• Pre-conditions– None

• Initiation– Search function selected

• Dialog– Search parameters selected, search initiated, unknown locations resolved, route list

displayed

• Termination – Route search complete (normal), unknown location (error)

• Post-conditions– Route list displayed (if available) or blank

Select Use Case Narrative• Assumptions

– Route list displayed

• Pre-conditions– At least one available route

• Initiation– Route selected from list

• Dialog– Select route, display details in map+timeline+text

• Termination – Display completed

• Post-conditions– Details displayed

Flight Finder Background• The traveler (or a system administrator) will first obtain schedule data

from JOSAC using their Web browser and store it on their hard drive in the received format. Upon program initiation, the Parse Sched use case will run automatically. Once that completes, the traveler may specify the origin, destination, radius around each, and a connection radius (or leave any of the default values set), earliest and latest times, and then initiate the search. Once the search completes, the traveler may step through the interesting routes one at a time, viewing information on which their decision might be based. Once one or more acceptable routes have been identified, the traveler can then contact the appropriate facilities directly to make travel arrangements.

Flies between Contains

FlightFinder Class DiagramRoute

GUI

Map

Timeline

Location

Airfield

Leg

AircraftType

Schedule

Flight*

1

1

*

2

1..9 11..**

*

0..1

1

1

1

1

*Sequence ofSequence of

Displayed in

Displayed in

Displayed in

2

1

Travelbetween Uses

Fli

es b

etw

een

*

0..11

1

Full FlightFinder Class DiagramRoute

GUI

Map

Timeline

Location

Airfield

Leg

AircraftType

Schedule

Flight

1

*

1..9 11..**

Sequence ofSequence of

2

1

Travelbetween

+addLeg(l:Leg)+summary():String

+search(p:Param)+display(r:Route)

+draw(r:Route)

+draw(r:Route)

-seats: integer-departureTime: Time-arrivalTime:Time+parse(s:String)+summary():String

-name:String-icaoIdentifier:String{4}

-latitude:double-longitude:double-timeZone:TimeZone+distanceTo(l:Location)

-flightNumber:String

+parse(s:String)

-updated:Time-source:URL

+parse(f:File)

-name:String-speed:int

+flightTime(o:Location, d:Location)

Con

tain

s

Use

s

Dis

play

ed in

Dis

play

ed in

1

1

Displayedin

1

*

2

*

D

FlightFinder Object Diagram1:Route

:GUI

:Map

:Timeline

DC:Location

Andrews:Airfield

:Leg

C-9B:AircraftType

Sep26:Schedule

AF302:Flight

-seats=3-departureTime=1200Z-arrivalTime:1400Z

-name=Andrews AFB-icaoIdentifier=KADW

-latitude:38-48N-longitude:076-51W-timeZone=EASTERN

-flightNumber:AF302

-updated:Sep 26/1200Z-source:http://www…

-name=C-9B-speed=450 knots

LA:Location

-latitude=33-57N-longitude=118-24W-timeZone=PACIFIC

Scott:Airfield

-name=Scott AFB-icaoIdentifier=KBLV

Lambert:Airfield

:Leg

-seats=34-departureTime=1600Z-arrivalTime=1900Z

-name=Lambert Field-icaoIdentifier=KSTL

LAX:Airfield

-name=LA Intl Airport-icaoIdentifier=KBLV

NV514:Flight

-flightNumber:NV514

O

D

O

O

D

1st

2nd

Key: O = Origin D = Destination

Class Critique

• Multiple instances must be possible– Each uniquely identifiable

• Can’t be subdivided into distinct classes

• Multiple attributes needed to describe

• No empty attribute values

• Methods needed– At least for creation and modification

Attribute Critique

• Naturally describes the object– Does not describe some other object

• Value will be known for some instances

• Value will never be empty

• Cannot be subdivided into smaller attributes

• One value, not a list of values

• Cannot be computed from other attributes

Relationships

• Object relationships– Has-a– Aggregation– Composition

• Class relationships– Generalization (“extends”)– “Implements”

Practice Exercise

• Create a Class Diagram for an academic transcript– Include a method to compute grade point average– Include a method to print the transcript

• Code (only) the transcript class in java– Include a main method that tests the class– Create stubs for any other needed classes

• Run your main method

Classes to Explore in the API

• String– Manipulate strings (e.g., to extract substrings)

• StringTokenizer– Pick apart strings (e.g., into words)

• GregorianCalendar– Dates and times

• Hashtable– Like arrays, but with any object as the index

Muddiest Point

On a blank sheet of paper, write a

single sentence that will convey

to me what you found to be the

most confusing thing that was

discussed during today’s class.

FlightFinder Class Diagram

Aircraft

type

display()

Airfield

nameicaoIdentifier

location

display()

Flight

flightNumberaircraft

legs

display()

Schedule

webpage

readFlight()readDate()display()

Location

latitudelongitude

distanceTo()timeZone()

Leg

flightdepartureFielddepartureTime

arrivalFieldarrivalTime

availableSeats

display()

Options

keyboardroutes

compute()display()

Route

legs

display()