1. COSC2767: Object-Oriented Programming
2017/4/16
COSC2767: Object-Oriented Programming
Haibin Zhu, Ph. D.
Associate Professor of CS, Nipissing University

2. Contact Me Haibin Zhu, Ph. D.
2017/4/16
Contact Me
Haibin Zhu, Ph. D.
Associate Professor of CS, Nipissing University
Room: A124A Ext.: 4434
URL:
Office Hour: Mon. & Tue.12:30pm-3:30pm; or by appointment

3. Course Description Covers the concepts of OOP languages and systems
2017/4/16
Course Description
Covers the concepts of OOP languages and systems
fundamental abstraction, modularity and encapsulation mechanisms in OOP
Advanced OOP concepts
polymorphism and operator overloading; message passing via generic functions; late versus early binding times; and inheritance mechanisms and their relationship to the type systems of programming languages.
Templates, Design Patterns
Java and Eclipses

4. How to get the goals Read and remember Think Practice Ask
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How to get the goals
Read and remember
Read the books, remember the language
Think
Think in objects, think in classes
Practice
Do as many coding as possible and make them running
Ask
me questions

5. Prerequisite Basic knowledge of Programming COSC1557, COSC1567
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Prerequisite
Basic knowledge of
Programming
COSC1557, COSC1567

6. 2017/4/16
The Textbooks Used
Timothy A. Budd, The Introduction to Object-Oriented Programming (3rd Edition), Addison-Wesley, 2001, ISBN
Avinash C. Kak, Programming with Objects: A comparative presentation of object-oriented programming with C++ and Java, John Wiley & Sons, ISBN:

7. 2017/4/16
Lecture 1
Thinking in Objects

8. Contents Methodology(Philosophy) Programming Techniques
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Contents
Methodology(Philosophy)
Programming Techniques
Object-Oriented Languages
Object and Large Systems

9. Thinking Methodology Induction (Abstract)
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Thinking Methodology
Induction (Abstract)
From specialization to generalization
From different dogs to create the word “dog”
Dog

10. Thinking Methodology Deduction(infer)
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Thinking Methodology
Deduction(infer)
From generalization to specialization
From the word “dog” you have learnt to know an animal is or not a dog.
DOG

11. Design Methodologies Functional decomposition (Top-Down)
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Design Methodologies
Functional decomposition (Top-Down)
The whole system is characterized by a single function, and then the function is decomposed into a set of functions in a process of stepwise refinement.

12. Functional decomposition
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Functional decomposition
The System
Studying
Function1
Function2
Function3
Desk
Table top
Filing cabinet
Bookshelves
Function11
Function12
Left drawer
Middle drawer
Right drawer

13. Design Methodologies Functional composition (bottom-up)
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Design Methodologies
Functional composition (bottom-up)
You can have different components of functions such as that from a function library
You can compose them into a module with a more significant function.

14. Functional composition
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Functional composition
The System
Studying
Function1
Function2
Function3
Desk
Table top
Filing cabinet
Bookshelves
Function11
Function12
Left drawer
Middle drawer
Right drawer

15. Functional (De)Composition
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Functional (De)Composition
Also known as top-down development
Widely deemed to be a “good thing”
Regard thing to be developed as a hierarchy
State top level, and decomposing into smaller functions.
Decomposition continues until code level.
Modules with well-defined semantics that can be directly implemented.
Procedures owe the data
Data plays a secondary role
Does not necessarily reflect the states of abstraction in the application.

16. Object-Orientation It is a kind of thinking methodology
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Object-Orientation
It is a kind of thinking methodology
Everything in the world is an object;
Any system is composed of objects (certainly a system is also an object);
The evolution and development of a system is caused by the interactions among the objects inside or outside the system

17. Everything in the world is an object
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Everything in the world is an object
A flower, a tree, an animal
A student, a professor
A desk, a chair, a classroom, a building
A university, a city, a country
The world, the universe
A subject such as CS, IS, Math, History, …

18. Any system is composed of objects
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Any system is composed of objects
A law system
A cultural system
An educational system
An economic system
An Information system
A computer system

19. The development of a system is caused by the interactions
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The development of a system is caused by the interactions
Nipissing University is developed by the interactions among:
students
professors
staffs
officers of Ontario
officers of Canada
… ...
Inside Nipissing
Outside Nipissing

20. 2017/4/16
Design Methodologies
Object-Orientation is one of the computational thinking methodologies.
Object-Orientation is a kind of design methodology(OOA/OOD)
Objects are the building blocks of the program(interface object(editor, menu, file, etc), data managing object(db), etc.).
Objects represent real-world abstractions within the application.

21. Design Methodologies Object-orientation supports both
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Design Methodologies
Object-orientation supports both
induction: objects -> a class
This needs the tools for OOA/OOD.
and deduction: a class ->objects
This needs the programmers to learn about the class library.

22. Design Methodologies Object-orientation supports both Top-down:
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Design Methodologies
Object-orientation supports both
Top-down:
from a superclass to subclasses;
complex objects to simple objects.
Bottom-up:
from subclasses to a superclass
Simple objects to complex objects

23. Object-Orientation “The World is Object-Oriented”
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Object-Orientation
“The World is Object-Oriented”
----Alan Kay said.
If you know the world, you know object-orientation.
So, object-orientation is easy.

24. Programming Programming is like writing.
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Programming
Programming is like writing.
If you can write a demonstration, you can make a program.
So, programming is also easy.
Then, Object-oriented programming equals easy + easy, that’s too(2) easy.

25. 2017/4/16
Programming
But, actually, programming is not so easy, because a real good program is not easily programmed. It needs the programmers’ lots of wisdom, lots of knowledge about programming and lots of experience.
It is like writing, to be a good writer needs lots of experience and lots of knowledge about the world.
Learning and practice are necessary.

26. Programming Techniques
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Programming Techniques
The evolution of programming techniques is
to make programming languages more expressive
to develop complex systems more easily

27. Programming Techniques
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Programming Techniques
Unstructured Programming
Procedural Programming
Modular & Structural Programming
Abstract Data Type
Object-Oriented Programming

28. Unstructured Programming
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Unstructured Programming
Usually, people start learning programming by writing small and simple programs consisting only of one main program. Here ``main program'' stands for a sequence of commands or statements which modify data which is global throughout the whole program.
Main Program
Data

29. 2017/4/16
Drawbacks
This programming technique can only be used in a very small program.
For example, if the same statement sequence is needed at different locations within the program, the sequence must be copied. If an error needed to be modified, every copy needs to be modified.
This has lead to the idea to extract these sequences(procedure), name them and offering a technique to call and return from these procedures.

30. Procedural Programming
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Procedural Programming
With procedural programming, you are able to combine sequences of calling statements into one single place.
A procedure call is used to invoke the procedure. After the sequence is processed, flow of control proceeds right after the position where the call was made .
Main
Program
Procedure

31. 2017/4/16
Procedures
With parameters and sub-procedures (procedures of procedures) , programs can now be written more structured and error free.
For example, if a procedure is correct, every time it is used it produces correct results.
Consequently, in cases of errors you can narrow your search to those places which are not proven to be correct.

32. Procedure Program view
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Procedure Program view
Now a program can be viewed as a sequence of procedure calls.
The main program is responsible to pass data to the individual calls, the data is processed by the procedures and the resulting data is presented.
Thus, the flow of data can be illustrated as a hierarchical graph, a tree.

33. Procedure Program view
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Procedure Program view
Main Program
Data
Procedure3
Procedure1
Procedure2

34. 2017/4/16
Modular Programming
Modular programming is subdividing your program into separate subprograms such as functions and subroutines.
With modular programming, procedures of a common functionality are grouped together into separate modules.
A program therefore no longer consists of only one single part. It is now divided into several smaller parts which interact through procedure calls and which form the whole program.

35. Main Program(Also a module)
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Main Program(Also a module)
Data
Module1 +
Module2 +
Data
Data
Data1
Data1
Data
Data2
Procedure2
Procedure3
Procedure1
The main program coordinates calls to procedures in separate modules and hands over appropriate data as parameters.

36. 2017/4/16
Modular Programming
Each module can have its own data. This allows each module to manage an internal state which is modified by calls to procedures of this module.
Each module has its own special functionalities that supports the implementation of the whole program.

37. Structural Programming
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Structural Programming
Also structured programming
A subset of procedural programming that enforces a logical structure on the program being written to make it more efficient and easier to understand and modify.
Certain languages such as Ada, Pascal, and dBASE are designed with features that encourage or enforce a logical program

38. Structural Programming
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Structural Programming
How many basic structures for programming?
Three Types of Structures in a structured program
Statement sequence(s1,s2,…,sn)
Branch(if-then-else)
Loop(for,do, and while loops)
Keep no goto!!! Keep modules!!!

39. Abstract Data Types (ADTs)
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Abstract Data Types (ADTs)
A set of data values and associated operations that are precisely specified independent of any particular implementation.
Come with Modular Programming
Abstraction
Model
Properties of Abstract Data Types
Abstract Data Types and Object-Orientation

40. Abstraction: Handling Problems
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Abstraction: Handling Problems
A process of generalization by reducing the information content of a concept or an observable phenomenon, typically in order to retain only information which is relevant for a particular purpose.
Try to understand the problem to separate necessary from unnecessary details:
You try to obtain your own abstract view, or model, of the problem.
This process of modeling is called abstraction.

41. Problem Model Abstraction
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Abstraction
Problem
Model
Two of the most important types of abstraction are the following:
Division into parts: Has-A abstraction
Division into specialization: Is-A abstraction

42. 2017/4/16
Has-A Abstraction
Division into parts takes a complex system, and divides into component parts, which can then be considered in isolation. Characterized by sentences that have the words ``has-a''
A car has-a engine, and has-a transmission
A bicycle has-a wheel
A window has-a menu bar
Allows us to drop down a level of complexity when we consider the component in isolation.

43. 2017/4/16
Is-a Abstraction
Is-a abstraction takes a complex system, and views it as an instance of a more general abstraction. Characterized by sentences that have the words ``is-a''
A car is a wheeled vehicle, which is-a means of transportation
A bicycle is-a wheeled vehicle
A pack horse is-a means of transportation
Allows us to categorize artifacts and information and make it applicable to many different situations.

44. 2017/4/16
Model
A model is an abstraction or conceptual object used in the creation of a predictive formula or a solution.
A model defines an abstract view to the problem and focuses only on problem related stuff and that you try to define properties:
the data which are affected;
the operations which are identified;
ADT is a kind of Model.

45. Abstract data types(ADT)
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Abstract data types(ADT)
Abstract data types are a partial solution to models
ADT defines the interface to a data abstraction without specifying implementation detail.

46. 2017/4/16
Properties of ADT
With abstraction, you create (1) a well-defined entity which can be properly handled.
These entities define (2) the data structure of a set of items.
For example, each administered employee has a name, date of birth and social number....

47. Properties of ADT(Cont’d)
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Properties of ADT(Cont’d)
The data structure can only be (3) accessed with defined operations.
This set of operations is called interface and is exported by the entity.
An entity with the properties just described is called an abstract data type (ADT).

48. ADT Abstract Data Type Operations Abstract Data Structure Interface
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Abstract Data Type
ADT
Abstract Data Structure
Interface
Operations

49. Definition (ADT) ADT is characterized by the following properties:
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Definition (ADT)
ADT is characterized by the following properties:
1. It exports a type.
2. It exports a set of operations. This set is called interface.
3. Operations of the interface are the only access mechanism to the type's data structure.
4. Axioms and preconditions define the application domain of the type.

50. Example: ADT List Type List.
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Example: ADT List
Type List.
The interface to instances of type List is defined by the interface definition file.
Operations: insert, get, append, delete,search,…

51. 2017/4/16
List
The application domain is defined by the semantics meaning of the provided operations. Axioms and preconditions include statements such as
``An empty list is a list.''
``Let l=(d1, d2, d3, ..., dN) be a list. Then l.append(dM) results in l=(d1, d2, d3, ..., dN, dM).''
``The first element of a list can only be deleted if the list is not empty.''

52. Encapsulation(1) Combine the data and the operations
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Encapsulation(1)
Combine the data and the operations
Enclosing of both variables and functions
Keep details of the data and operations from the users of the ADT
Once you have created an ADT for complex numbers, say Complex, you can use it in the same way like well-known data types such as integers.

53. Encapsulation(2) Allows Modularity Controlled access to data
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Encapsulation(2)
Allows Modularity
Controlled access to data
Separates implementation from interface
It extends the built-in types

54. Object-Oriented Programming
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Object-Oriented Programming
Object is derived from abstract data type
Object-oriented programming has a web of interacting objects, each house-keeping its own state.
Objects of a program interact by sending messages to each other.

55. Object1 Data1+Procedures1 Object2 Data2 + Procedures2 Data Data1
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Object1
Data1+Procedures1
Object2
Data2 + Procedures2
Data
Data1
Object3
Data3 + Procedures3
Object4
Data4 + Procedures4

56. Object-Oriented Programming
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Object-Oriented Programming
In object-oriented programming , instead of calling a procedure which we must provide with the correct handle, we would directly send a message to the object in questions.
Roughly speaking, each object implements its own module.

57. Object-Oriented Programming
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Object-Oriented Programming
Each object is responsible to initialize and destroy itself correctly.
Consequently, there is no longer the need to explicitly call a creation or termination procedure.

58. Kay’s Description of OOP
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Kay’s Description of OOP
Everything is an object
Objects perform computation by making requests of each other through the passing of messages
Every object has it's own memory, which consists of other objects.
Every object is an instance of a class. A class groups similar objects.
The class is the repository for behavior associated with an object
Classes are organized into singly-rooted tree structure, called an inheritance hierarchy.

59. ADT and Object-Orientation
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ADT and Object-Orientation
ADTs allows the creation of instances with well-defined properties and behavior.
In object-orientation, ADTs are referred to as classes.
Therefore, a class defines properties of objects which are the instances in an object-oriented environment.

60. ADT and Object-Orientation(2)
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ADT and Object-Orientation(2)
ADTs define functionality by putting main emphasis on the involved data, their structure, operations as well as axioms and preconditions.
Object-oriented programming is ``programming with ADTs'': combining functionality of different ADTs to solve a problem.
Therefore instances (objects) of ADTs (classes) are dynamically created, destroyed and used.

61. ADT and Object-Orientation(3)
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ADT and Object-Orientation(3)
ADTs still lack self-reference and conceptual locality of objects.
Data types and operations are almost objects, but need to put them together and give the result a name which can be self-referenced.

62. A Formula Object-Orientation = Object (Abstraction) +
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A Formula
Object-Orientation =
Object (Abstraction) +
Class (ADT & Classification) +
Inheritance (Reusing) +
Dynamic Binding (Polymorphism, Flexibility)

63. Inheritance(Hierarchy)
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Inheritance(Hierarchy)
Expresses commonality among objects
Allows code reusability
Highlights Generalization/Specialization relationships
We will learn more in the following lectures.

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Polymorphism
The ability of objects to respond differently to the same message or function call.
We will discuss more in the following lectures.

65. Object-Orientation Evolution
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Object-Orientation Evolution
Modules
Information hiding
Data encapsulation
Abstract data types
Classes and Objects

66. 2017/4/16
Simply Remember
Encapsulation(Data & Operations)--- A technique for Information Hiding-----the users of the objects could not see the details of the data and operations of the objects.
Data Abstraction ---- the procedure to find a class from objects.
Abstract Data Type---- Class.

67. Object-Oriented Languages
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Object-Oriented Languages
An object-based programming language is one which easily supports object-orientation.
Smalltalk: , Alan Kay
C++:1986, Bjarne Stroustrup
Java:1992 (Smalltalk + C++), James Gosling
C#:
Developed at Microsoft by Anders Hejlsberg et al, 2000
Event driven, object oriented, visual programming language (C++ and Java)
Others:
Effile, Objective-C, Ada, ...

68. Programming in the Small and Programming in the Large
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Programming in the Small and Programming in the Large
Programming in the Small:
One programmer, understands everything from top to bottom.
Major problem is the development of algorithms.
Programming in the Large:
System is developed by large team of programmers
Major problems are management of details and communication between programmers and between their respective software subsystems.

69. Objects and Large Software Systems(1)
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Objects and Large Software Systems(1)
Programming in the Small:
One programmer, understands everything from top to bottom.
Major problem is the development of algorithms.
Programming in the Large:
System is developed by large team of programmers
Major problems are management of details and communication between programmers and between their respective software subsystems.

70. Objects and Large Software Systems(2)
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Objects and Large Software Systems(2)
Object view
Makes systems more intuitively understandable
Unifies design and programming method
Initial program thoughts are informal objects-and-interactions descriptions, even when using a non-OO language.
Divides code into logical chunks individuals of a team can be experts in, and outsiders can understand via interfaces
Allows "off the shelf" code libraries to be reused
Supports code evolution: internals can always be re-written as long as interface stays the same

71. Objects and Large Software Systems(3)
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Objects and Large Software Systems(3)
So, in large software system, we need more CONCEPTS and STRUCTURES of object-orientation than PROGRAMMING SKILLS
Those are OOA(Object-Oriented Analysis) and OOD(Object-Oriented Design), that will be discussed more deeply in Software engineering or Software designing methodology.

72. Summary Methodology (Philosophy) Programming Techniques
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Summary
Methodology (Philosophy)
Programming Techniques
Object-Oriented Languages
Object and Large Systems

73. 2017/4/16
The End
The End of Lecture 1