daad project “joint course on oop using java” on object oriented modeling in java (why &...

DAAD project “Joint Course on OOP using Java”

On Object Oriented modeling in Java On Object Oriented modeling in Java (Why & How)(Why & How)

Ana Madevska BogdanovaAna Madevska Bogdanova

Institute of informaticsInstitute of informaticsFaculty of Natural Sciences and MathematicsFaculty of Natural Sciences and Mathematics

Skopje, MacedoniaSkopje, Macedonia

DAAD project „Joint Course on OOP using Java“ © 2

AgendaAgenda

The motivation The need of introducing design patterns in

the first year of studies Incorporation in the concepts of the existing

OOP course Expected results


The motivationThe motivation

To start earlier with Java (DSA will improve) To introduce design patterns in OOP


The motivationThe motivation

The first two courses • Structured programming• Object oriented and visual programming

C++ is the represent of a OOP language The second course

• Encaptulation• Inheritance• Polymorphism


Where is Java in the curriculum?Where is Java in the curriculum?

Java is in the course Data Structures and Algorithms• Third semester• The course is too much• Introductory level of Java while listening to the

theory about Data structures

Discrepancy between programming the data structures and the theory

Solution?


The solutionThe solution

We will introduce Java in the second semester within the course OO programming• The students are ready to start to program data

structures immediately within the course DSA• No discrepancy


AgendaAgenda

The motivationThe need of introducing design

patterns in the first year of studies Incorporation in the concepts of the existing



Another existing problem…Another existing problem…

Thinking in the design pattern level Introduced in the course of software

engineering in the 5th semester• Software design and architecture

In the first two programming courses the students mind is focused only on technical clarity in developing the OO system


Idea – introduce design patterns in the Idea – introduce design patterns in the first semesterfirst semester

In the OO programming course we can introduce some problems and discuss them with the students

• How to create OO model – to go through the process OO modeling


Why do that?Why do that?

Till now• We give them ready OO model and ask the

students to program it and use- Encaptulation- Polymorphism- Inheritance

New idea• Ask the students to BUILD the OO model for a

given problem• To broaden their point of view for the proper

programming• To be ready to learn more design patterns in the

latter courses


The levelsThe levels

1. OO basics• encapsultion, polymorphism, inheritance

2. OO principles 3. OO patterns

• 1. Strategy- Defines a family of algorithms, encapsulates each

one, and makes them interchangable- let the algorithm vary independently from clients

that use it


Why design patterns?Why design patterns?

This is what the students should learn in the first year of their studies.

Students learn that applying design patterns is like reusing experience. One can apply successful patterns to develop new software without reinventing new solution strategies.


How to do that?How to do that?

Teach Java course- Encaptulation- Polymorphism- Inheritance

Go further• Introduce a design pattern• Give a problem

- Start with straightforward model- Change something- Remodeling- … solution would be one of the design patterns


AgendaAgenda

The motivation The need of introducing design patterns in

the first year of studies Incorporation in the concepts of the existing



The idea is to learn ONE design pattern Starting from scratch Choosing interesting problem

• Discuss with the students every step of developing the model by putting different subproblems as new requirements for the model

• The model must develop with the new requirements


1. The strategy pattern1. The strategy pattern

The idea is to guide the student through the process of implemeting the right Pattern Design to create the right OO model for the given problem.

Along the way they will understand the main OO principles - why to develop the software in that particular way1. Encapsulate what varies2. Program to interfaces, not implementation3. Favor composition over inheritance


Simple problemSimple problem

We chose a simple problem To explain the students that the only thing

that we can be certain about - is the change in every software development

No matter how well one designs an appliication, it must grow and develop over time

So, the first design pattern is about flexibility in the OO model


Inheritance?Inheritance?

To point the student that inheritance doesn’t always work well• Request - the behavior keeps changing across

the subclasses, and it is not appropriate every subclass to have that behavior.


The FIRST design principleThe FIRST design principle

Part of code that changes• New requirements• It is a behavior that should be parted from the rest

of the code

SO, the students should identify the aspects of the application that vary and separate them from the parts that don‘t change• “encapsulate “ it so it won‘t affect the rest of

the code

The result is• Less unintended consequences when changing the

code• More flexibility in the system


The SECOND design principle The SECOND design principle

We introduce another design principleProgram to an interface, not the

implementation The different behaviors will live in a

separate classes That way, the classes won‘t need to know

any of the implementation details for their own behaviors


The realizationThe realization

We will use an interface to represent each behavior and each implementation of the behavior will implement one of those interfaces.

Program to an interface really means program to a supertype

The concept of interface must not to be mixed up with the JAVA construct interface .

You can program to an interface, withouth using the actual construct interface.

We want to exploit polymorphism


Another difference with the current OOP Another difference with the current OOP coursecourse

We also plan to extend the knowledge of the students about the class relations in order to build more flexible models

Discovering class relations• Association

• Aggregation and Composition

• Inheritance(revisited)


Has-A can be better that Is-AHas-A can be better that Is-A

The THIRD design principle Instead of inheriting a certain behavior, the

objects get their behavior by composing with the right behavior object.

The students learn the third design principle• …favor composition over inheritance• …creating systems using composition provides a

great deal of flexibility.


AgendaAgenda

The motivation• To start earlier with Java (DSA will improve)• introducing design patterns

The need of introducing design patterns in the first year of studies

Incorporation in the concepts of the existing OOP course

Expected results


Expected results of introducing JAVA and Expected results of introducing JAVA and design patterns in JAVAdesign patterns in JAVA

As mentioned in the motivation part• More prepared students to embrace the higher

level of producing OO modeling early - in their first OO course

• They will be ready to learn more OO design patterns in the latter courses

• Ready to develop OO models on their own in the different courses in the latter semesters.

• learning JAVA in this course will make DSA course more comprehendible in the third semester- Students wouldn't have to learn the basics of

JAVA, they will use it for simulating data structures covered with the course


Thank you for your attention

daad project “joint course on oop using java” on object oriented modeling in java (why &...

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