1. Object-Oriented Software Development: Class Diagrams and Its Implementation
Chih-Ping Chu
Dept. of Computer Science & Information Engineering
National Cheng Kung University

2. Outline Features of object-oriented software
Developing OO systems based on models
UML diagrams
Essentials of class diagrams
Implementing class diagrams

3. Models are used for: - leading software engineers to have
insights about the system
- providing abstraction
- helping create designs
- permitting analysis and review of those
designs. (check design)
- being the core documentation describing
the system.

4. UML diagrams Class diagrams - describe classes and their relationships
Interaction diagrams
- show the behaviour of systems in terms of
how objects interact with each other
State diagrams and activity diagrams
- show how systems behave internally
Component and deployment diagrams
- show how the various components of
systems are arranged logically and physically

5. Class diagrams

6. Interaction diagrams

7. State diagrams and activity diagrams

9. Component and deployment diagrams

10. Essentials of UML Class Diagrams
The main symbols shown on class diagrams are:
Classes
- represent the types of data themselves
Associations
- represent linkages between instances of classes
Attributes
- are simple data found in classes and their instances
Operations
- represent the functions performed by the classes and their instances
Generalizations
- group classes into inheritance hierarchies

12. Implementing Class Diagrams in Java
- Attributes are implemented as instance variables
- Generalizations are implemented using extends
- Interfaces are implemented using implements
- Associations are normally implemented using
instance variables
- Divide each two-way association into two one-
way associations so each associated class has an
instance variable.

13. - For a one-way association where the multiplicity at the other end is ‘one’ or ‘optional’
- declare a variable of that class (a reference)
- For a one-way association where the multiplicity at the other end is ‘many’:
- use a collection class implementing List, such as Vector

14. An example: A Flight Booking System

16. An example: A Flight Booking System

17. Creating an association class, given two existing objects
class Passenger {
private ArrayList<Booking> bookings = new ArrayList<Booking>(0);
private String name;
public void makeBooking(SpecificFlight flight, int seatNumber)
new Booking(this, flight, seatNumber); }
void addLinkToBooking(Booking bookOne) // link booking
bookings.add(bookOne);

18. class Booking //association class{
Passenger passenger; // due to one to one relation
SpecificFlight flight; //due to one to one relation
int seatNumber;
Booking(Passenger passenger, SpecificFlight flight, int seatNumber)
this.passenger = passenger;
this.passenger.addLinkToBooking(this);
this.flight = flight;
this.flight.addLinkToBooking(this);
this.seatNumber = seatNumber; }

19. void addLinkToBooking(Booking bookOne) booking.add(bookOne); }
class SpecificFlight {
private ArrayList<Booking> booking = new ArrayList<Booking>(0);
private String name;
void addLinkToBooking(Booking bookOne)
booking.add(bookOne); }

21. Making a bi-directional link between two existing objects;
class SpecificFlight {
private Calendar date;
private RegularFlight regularFlight;
...
// Constructor that should only be called from
// addSpecificFlight
SpecificFlight( Calendar aDate, RegularFlight aRegularFlight)
date = aDate;
regularFlight = aRegularFlight; }

22. class RegularFlight {
private List specificFlights;
...
// Method that has primary responsibility
public void addSpecificFlight(Calendar aDate)
SpecificFlight newSpecificFlight;
newSpecificFlight = new SpecificFlight(aDate, this);
specificFlights.add(newSpecificFlight); }

24. Creating an object and linking it to an existing object
class SpecificFlight {
private FlightLog log;
private RegularFlight regularFlight;
...
public void createFlightLog ()
log = new FlightLog(); }

25. class FlightLog {
...
FlightLog () // constructor }

26. Searching for an associated instance
import java.util.Iterator; class SpecificFlight { private ArrayList<EmployeeRole> employees = new ArrayList<EmployeeRole>(0); private EmployeeRole anEmployee; ... public EmployeeRole findCrewMember (String name) for (Iterator<EmployeeRole> iterator = employees.iterator(); iterator.hasNext();) anEmployee = (EmployeeRole) iterator.next(); if anEmployee,getname() == name return anEmployee; }

27. class EmployeeRole {
private String name;
...
public String getName()
return name;
} () }