Design Patterns in the course

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Design Patterns in the course OOP in Java -
first experiencesAna Madevska
BogdanovaInstitute of informaticsFaculty of
Natural Sciences and MathematicsSkopje, Macedonia
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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

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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

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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

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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

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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

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Introducing design patterns in the first semester

• What if we introduce DP in the FIRST semester?
• Last years 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

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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!

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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

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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

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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

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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

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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

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1. 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

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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

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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
  problems solution.

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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 wasnt
  covered in the previous material from the course

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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

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Facts

• Till last year C
• This year Java
• Different students
• The number of measured results (from the Javas
  exams) is not statistically significant.

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Two ways of measuring the results

• 1. Too few data at the presenters disposal
• Students results
• 2008, 2009 with C
• 2010 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

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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?

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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
• 1 -
• 2. Do you need more previous knowledge to be able
  to understand DP part of the course?
• YES 33
• NO 67

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• 3. 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

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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 werent 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

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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

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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.

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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

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Conclusions

• 1. Too few data at the presenters 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

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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

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• Thank you!
• ? ?