DAAD project “Joint Course on OOP using Java” Design Patterns in the course ‘OOP in Java’ - first experiences 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 of the design patterns in the concepts of the existing OOP course  Expected results

DAAD project „Joint Course on OOP using Java“ © 3 The motivation (last year)  We had a problem with the course Data Structures and Algorithms (DSA) - third semester in the same course -First learn Java -Then data structures in Java  The reality (till last year): The first two courses in the first year -I. Structured programming (C++) -II. Object oriented and visual programming (C++) The second course, OOP -Encaptulation -Inheritance -Polymorphism -Solving problems = coding when given OO Design - scheme

DAAD project „Joint Course on OOP using Java“ © 4 The solution of the problem  Last semester We introduced Java in the course ‘Object oriented and visual programming‘ It is THE first OOP course It is the second semester

DAAD project „Joint Course on OOP using Java“ © 5 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“ © 6 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“ © 7 Introducing design patterns in the first semester  What if we introduce DP in the FIRST semester?  Last year’s idea: 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 of OO modeling 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“ © 8 The realization of the idea  NOW: 1. the existing course in OO programming is shifted towards  Java. 2. The general plan of the course stayed the same -Encapsulation -Polymorphism -Inheritance With a CHANGE: we replaced some topics of the previous ‘OOP with C++’ course with the introduction of the … DESIGN PATTERNS!

DAAD project „Joint Course on OOP using Java“ © 9 What did we change with the course?  First: Learn about -Encapsulation -Polymorphism -Inheritance  The introduction of Design Patterns The students were presented a problem and asked to BUILD the OO model

DAAD project „Joint Course on OOP using Java“ © 10 Agenda  The motivation  The need of introducing design patterns in the first year of studies  Incorporation of the concepts in the existing OOP course  Expected results

DAAD project „Joint Course on OOP using Java“ © 11 Some facts  The design pattern part was incorporated in the last 5 classes of the course.  By that time students had the opportunity to experience the OO programming Programming in NetBins environment

DAAD project „Joint Course on OOP using Java“ © 12 The levels of the OOP with Java - course  1. OO basics encapsultion, polymorphism, inheritance, also: interfaces, downcasting, exceptions  2. OO principles  3. Introducing the OO design 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“ © 13 How we did that?  So, after the common Java beginners course Introduction of the DESIGN PATTERNS  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  Along the way the students 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“ © 15 Simple problem  We chosed 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 design pattern we worked with was about flexibility in the OO model

DAAD project „Joint Course on OOP using Java“ © 16 Have we succeeded?  On every step of the presentation, students were asked a question – how to proceed.  Usually there were 2-3 ideas Additional question leaded to the correct answer The class had a good dynamics, everybody understood the ‘story’ and the line of the problem’s solution.

DAAD project „Joint Course on OOP using Java“ © 17 Was there a lot of new material?  Almost everything that was needed for the introduction of this Pattern Design was already incorporated into the course Classes with inheritance Interfaces -within the inheritance model  The new part: The need of building classes of behavior that are different for the subclasses from the Problem hierarchy New hierarchy of behavioral classes -In the subclasses is the different behavior Introduction of variables in the Problem hierarchy classes that will connect with the classes from the Behavior hierarchy ONLY the last part was a technique that wasn’t covered in the previous material from the course

DAAD project „Joint Course on OOP using Java“ © 18 Agenda The motivation  The need of introducing design patterns in the first year of studies  Incorporation of the concepts in the existing OOP course  Expected results

DAAD project „Joint Course on OOP using Java“ © 19 Facts  Till last year C++  This year Java  Different students  The number of measured results (from the Java’s exams) is not statistically significant.

DAAD project „Joint Course on OOP using Java“ © 20 Two ways of measuring the results  1. Too few data at the presenter’s disposal Students results -2008, 2009 with C with Java, still not finished with the exams -No statistical significance in comparing the results from different generations  The first year students 2 Groups of 80 students  2. Using a questionnaire How did everybody like the introduction to the design patterns? The ultimate answer will be answered after the next course “Software design and architecture” – in their 5-th semester – next year

DAAD project „Joint Course on OOP using Java“ © 21 The questions  1. What is the level of difficulty of the course content? 1(easy) to 5 (very hard) 2. Do you need more previous knowledge to be able to understand this part of the course? 3. Was it difficult to learn about a pattern design? 4. Was it revealing to go further, not only to learn the OOP technique?

DAAD project „Joint Course on OOP using Java“ © 22 The questions  1. What is the level of difficulty of the course content? 1(easy) to 5 (very hard) 5 15% 4 34% 3 42% 2 9 % Do you need more previous knowledge to be able to understand DP part of the course? YES 33% NO 67%

DAAD project „Joint Course on OOP using Java“ © Was it difficult to learn about a pattern design? YES 66% NO 34% 4. Was it revealing to go further, not only to learn the OOP technique? YES 100% NO 0%

DAAD project „Joint Course on OOP using Java“ © 24 In other words  100 % - found to be interesting to talk about the problem and the DP  85% - could understand the problem and to follow the line of the solution  15% - understood the complete DP we worked through Including the new elements that weren’t covered in the previous sections of the OOP course The same percentage of students that understand ANY new concept when it is introduced for the first time

DAAD project „Joint Course on OOP using Java“ © 25 About the understanding part…  Students were asked this questions immediately after the finishing of the DP part of the course  Bigger percentage of correct answers on the exam After they have studied the problem on their own

DAAD project „Joint Course on OOP using Java“ © 26 Expected results of introducing JAVA and design patterns in JAVA  As mentioned in the motivation part 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.

DAAD project „Joint Course on OOP using Java“ © 27 Expected results of introducing JAVA and design patterns in JAVA  Learning JAVA in this course will make ‘Data Structures and Algorithms’ 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  Next semester (starting this month) we will see if the students are ready to start to program data structures immediately within the course DSA

DAAD project „Joint Course on OOP using Java“ © 28 Conclusions  1. Too few data at the presenter’s disposal to see if this approach (Java & Design Pattern) is success -No statistical significance in comparing the results from past generations  2. EASY transition from C++ to Java  3. The questionnaire has showed that introducing the DP has broaden students mind  4. Through right example with the leading from the teacher students are able to Understand the problem To see the limitations of the ‘obvious’ solution To suggest change in the current solution To clarify the right way by discussion and ‘clever’ questions from the teacher Understand the whole process of thinking to come to the right solution Hopefully to recognize this pattern in other problems and to use this pattern as a solution at hand

DAAD project „Joint Course on OOP using Java“ © 29 Yet to see if …  … the next course DSA (the following semester) will be easier to comprehend  … OOP will be easier understood with Java or C++  … the SE course where more design patterns are thought will be easier to be understand Easier to learn more of Design Patterns

DAAD project „Joint Course on OOP using Java“ © 30 Thank you! ? ?