DAAD project “Joint Course on OOP using Java” On Object Oriented modeling in Java (Why & How) Ana Madevska Bogdanova Institute of informatics Faculty of Natural Sciences and Mathematics Skopje, Macedonia

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

DAAD project „Joint Course on OOP using Java“ © 3 The motivation  To start earlier with Java (DSA will improve)  To introduce design patterns in OOP

DAAD project „Joint Course on OOP using Java“ © 4 The 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

DAAD project „Joint Course on OOP using Java“ © 5 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?

DAAD project „Joint Course on OOP using Java“ © 6 The 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

DAAD project „Joint Course on OOP using Java“ © 7 Agenda  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

DAAD project „Joint Course on OOP using Java“ © 8 Another existing problem…  Thinking in the design pattern level  Introduced in the course of software engineering in the 5 th 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

DAAD project „Joint Course on OOP using Java“ © 9 Idea – introduce design patterns in the first 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

DAAD project „Joint Course on OOP using Java“ © 10 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

DAAD project „Joint Course on OOP using Java“ © 11 The 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

DAAD project „Joint Course on OOP using Java“ © 12 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.

DAAD project „Joint Course on OOP using Java“ © 13 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

DAAD project „Joint Course on OOP using Java“ © 14 Agenda  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

DAAD project „Joint Course on OOP using Java“ © 15  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

DAAD project „Joint Course on OOP using Java“ © 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 way 1. Encapsulate what varies 2. Program to interfaces, not implementation 3. Favor composition over inheritance

DAAD project „Joint Course on OOP using Java“ © 17 Simple 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

DAAD project „Joint Course on OOP using Java“ © 18 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.

DAAD project „Joint Course on OOP using Java“ © 19 The 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

DAAD project „Joint Course on OOP using Java“ © 20 The SECOND design principle  We introduce another design principle  Program 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

DAAD project „Joint Course on OOP using Java“ © 21 The 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

DAAD project „Joint Course on OOP using Java“ © 22 Another difference with the current OOP course  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)

DAAD project „Joint Course on OOP using Java“ © 23 Has-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.

DAAD project „Joint Course on OOP using Java“ © 24 Agenda  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

DAAD project „Joint Course on OOP using Java“ © 25 Expected results of introducing JAVA and design 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

DAAD project „Joint Course on OOP using Java“ © 26  Thank you for your attention