1. Introduction to Object-Oriented Concepts…

2. What is this class about?
Three Questions
What is this class about?
Why does it matter?
How does 331 fit in cs curriculum?

3. Computational Problems
What is computer science?
Computer
Solution? ?
Computational Problems
What is this class about?

4. Solving Problems With The Aid of Computers
Communication?
Programming language
Machine language
What is this class about?

5. Solving Problems With The Aid of Computers
Programs
Programming language
Machine language
What is this class about?

6. Solving Problems With The Aid of Computers
Programs
Programming language
Machine language
Address
Machine Instruction   1   2   3   4  
What is this class about?

7. Assembly Instructions
Solving Problems With The Aid of Computers
Programs
Programming language
Machine language
Assembly Instructions
push cs
pop ds
mov ah, 9
int 21h
sloop:
What is this class about?

8. Solving Problems With The Aid of Computers
Programs
Programming language
Machine language
High-level Program
for(int i=0; i<10; i++)
System.out.println(list[i]);
What is this class about?

9. Procedural Programming
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
#include<stdio.h>
// function prototype, also called function declaration
float square ( float x );                              
// main function, program starts from here
int main( )               {
    float m, n ;
    printf ( "\nEnter some number for finding square \n");
    scanf ( "%f", &m ) ;
    // function call
    n = square ( m ) ;                      
    printf ( "\nSquare of the given number %f is %f",m,n ); }
float square ( float x )   // function definition
    float p ;
    p = x * x ;
    return ( p ) ;
What is this class about?

10. Structure of a Procedural Program
Procedural Programming
Structure of a Procedural Program
function-1()
main()
In procedural programming a program consists of a set of functions.
The first function to be executed is often called ‘main’.
What is this class about?

11. Challenges of Procedural Programming
Handling large complex programs.
create
reuse
evolve
Large software systems: 4 x 106 – 100 x 106
What is this class about?

12. Dimensions of Software Complexity
Challenges of Procedural Programming
Dimensions of Software Complexity
Algorithmic
Functional
Structural
structure of the data
structure of the program
Communicational
Computational
etc.
What is this class about?

13. Complex programs require systematic development
Challenges of Procedural Programming
Complex programs require systematic development
Requirements Analysis
Software Design
Implementation
Testing
Deployment
Evolution
What are the most difficult phases of the software process?

14. Complex programs require systematic design
Challenges of Procedural Programming
Complex programs require systematic design
Requirements Analysis
Software Design
Implementation
Testing
Deployment
Evolution
Software design is arguably the most difficult phase of the software lifecycle.

15. Programming Paradigm Evolution
Object-Oriented Programming, C++, Java
Procedural Programming: C, Pascal, Fortran
Assembly Language Programming
Machine Language Programming
OOP provides better tools for developing and managing complex programs.
What is this class about?

16. Object-Oriented Programming using Java
What is this class about?
Object-Oriented Programming using Java
OOP provides better tools for developing and managing complex programs.
What is this class about?

17. Why does it matter?
Object-Oriented Programming (OOP) is a dominant programming paradigm
Leverage benefits of Object-Oriented Programming
OOP provides better tools for developing and managing complex programs.
What is this class about?

18. What is this class about?
Three Questions
What is this class about?
Why does it matter?
How does 331 fit into cs curriculum?

19. How does 331 fit into cs curriculum?
131 – basic procedural programming
231 – basic structures for managing data
331 – you learn basic OOP
Operating systems (use OOP)
380 – algorithm design (use OOP)
450 – teams develop complex software (use OOP)
455 – includes OO databases

20. Outline Course overview Getting to know you/me
Introduction to Object Oriented Programming (OOP) Concepts
Encapsulation
Classes & Objects
Composition
Inheritance
Polymorphism

21. Getting to Know You Name Background Where from Programming background
The Man without a Face, oil on panel, 11x14, 2005 – Dae-Woong Nam
Name
Background
Where from
Programming background
Languages

22. Fundamental Concepts of OOP
Encapsulation
Inheritance
Polymorphism

23. Understanding Object Oriented Programming
In machine language programming – programs are sequences of bits.
In assembly language programming – programs are pieces of code.
In procedural programming – programs are collections of interacting functions.
In OOP – programs are collections of interacting objects.

24. Program Structure: OOP vs Procedural
Object-Oriented Program
global data
function-1()
main()
Procedural Program …
function-1()
main()
global data
Class 1 …
function-1()
global data
Class 2 …
function-1()
global data
Class 3

25. Requirements Analysis
OOP & Design
OOP simplifies software design because OOP uses larger abstraction units than procedural programming.
Requirements Analysis
Software Design
Implementation
Testing
Deployment
Evolution

26. Motivating Example Bank Client StockBroker
In OOP objects in the real world are modeled as objects in software world.
Bank
StockBroker
Client
Programming languages represent real world objects as software classes and objects.
OOP narrows the semantic gap between real world and software world.

27. Example of a Java Class public class Account { private int accNumber;
private double balance;
public boolean deposit(double amount){
if(amount > 0){
this.balance += amount;
return true; }
return false;
public boolean withdraw(double amount){
if(this.balance >= amount){
this.balance -= amount;
}//end of class

28. Method Signatures
The following is all the user needs to know to effectively use a method:
The name of the method
The parameters passed to the method
The return type of the method
What he method does

29. Example of a Java Class public class Account { private int accNumber;
private double balance;
public boolean deposit(double amount){
if(amount > 0){
this.balance += amount;
return true; }
return false;
public boolean withdraw(double amount){
if(this.balance >= amount){
this.balance -= amount;
}//end of class

30. Abstraction & Software Design
In procedural programming:
Functions are black boxes.
all a user needs to know to effectively use a method is the method signature:

31. Abstraction & Software Design
In procedural programming:
Functions are black boxes.
all a user needs to know to effectively use a method is the method signature:
In OOP:
Classes and functions are black boxes.
all a user needs to know to effectively use a class is the class interface:
The class interface includes a list of method signatures
The service the class provides

32. O-O Programming
A fundamental advantage of O-O programming is that the data and the operations that manipulate the data are both contained in the object.
For example, when an object is transported across a network, the entire object, including the data and behavior, goes with it.

33. Class Fundamentals & Modeling in UML
Account
deposit(amount:double):boolean
withdraw(amount:double):boolean
accNumber:int
balance:double
In OOP, class = methods + data
We call the data ‘attributes’ of the class

34. IN-Class Exercise
Draw a UML diagram for a class that represents books in a library software system.
Name
Attributes – define data the class will use.
Operations/methods/functions – define the class behavior.

35. Object Data
The data stored within an object represents the state of the object.
In O-O programming terminology, this data is called attributes.
Eg. 1: UML account class with account number, balance.
E.g. 2: Java account class with account number, balance.

36. Object Data in Java
In Java data/variables must be declared before use.
Java uses explicit typing.
eg. Java account class with attributes: account number and balance.
public class Account {
private int accNumber;
private double balance; … }
}//end of class

37. Fundamental Concepts of OOP
Continue …
Fundamental Concepts of OOP
Encapsulation
Inheritance
Polymorphism

38. Encapsulation
One of the primary advantages of using objects is that the object need not reveal all its attributes and behaviors.
In good O-O design (at least what is generally accepted as good), an object should only reveal the interfaces needed to interact with it.

39. Encapsulation
Details not pertinent to the use of the object should be hidden from other objects.
This is called encapsulation.
Encapsulation is realized using classes and objects
class = variables + methods

40. Encapsulation & Interfaces
The complete list of all the methods a user may call to get a desired behavior from an object is called the provided or public interface of the class/object. This interface also includes any publicly accessible attributes.
Interfaces do not normally include attributes only methods.
The interface should completely describe how users of the class interact with the class.
methods that are part of the interface are designated as public.

41. Encapsulation & Interfaces
public class Account {
private int accNumber;
private double balance;
Public String alias;
public void deposit(double amount){
this.balance += amount; }
public void withdraw(double amount){
this.balance -= amount;
private int changeAccNumber(int accNum){
this.accNumber = accNum;
private void getAccountInfo(){
//actual code here
}//end of class
What is the provided interface for this class?

42. Encapsulation & Interfaces
Normally, if a user needs access to an attribute, then a public method is created to return the attribute.
To support OO design, OOP languages facilitates the creation of:
Classes = attributes + methods
Interfaces = list of method signatures

43. Encapsulation & Interfaces
Example of an interface
public interface IAccount {
public boolean deposit(double amount);
public boolean withdraw(double amount);
public int getAccNumber();
public double getBalance();
public void setBalance(double balance); }

44. Encapsulation: What Exactly Is a Class?
A class is a blueprint for an object.
The process of creating an object from a class is called instantiation.
When you instantiate an object, you use a class as the basis for how the object is built.
NB: primitive types vs classes.

45. Encapsulation: Declaring variables in Java
Type of data is explicitly used:
int x;
float y, z;
Integers and floats are built-in types
Declare two instances of the Account class:
Account obj1, obj2;
Classes are user-defined types.

46. Fundamental Concepts of OOP
Encapsulation
Inheritance
Polymorphism

47. Inheritance
Inheritance allows a class to inherit the attributes and methods of another class.
This allows you to create brand new classes by abstracting out common attributes and behaviors.

48. Mammal Hierarchy
Inheritance is sometimes described as the “Is A” relationship. For example, a dog is a mammal.

49. Mammal Hierarchy

50. Superclasses and Subclasses
The superclass, or parent class, contains all the attributes and behaviors that are common to classes that inherit from it.

51. Superclasses and Subclasses
A shape hierarchy
The inheritance arrow shown here is called “Generalization/Sp ecialization” in UML

52. Inheritance Example in Java
Most common form is to use the extends keyword
public class Dog extends Mammal{
//class body }

53. Fundamental Concepts of OOP
Encapsulation
Inheritance
Polymorphism

54. Polymorphism
Polymorphism means many forms. Java provides two forms of polymorphism:
Method overloading
Operator overloading.

55. Polymorphism Method overloading
Multiple methods with the same name but having different method signatures.
public void add(int a, int b);
public void add(int a, int b, int c);
public void add(String a, String b);

56. Polymorphism Operator overloading.
One operator may be used for different operations
versus “I love ” + “you Mom.”

57. Composition
It is natural to think of objects as containing other objects.
A television set contains a tuner and video display.

58. Composition A computer contains video cards, keyboards, and drives.
Although the computer can be considered an object unto itself, the drive is also considered a valid object.

59. Composition
In fact, you could open up the computer and remove the drive and hold it in your hand.
Both the computer and the drive are considered objects. It is just that the computer contains other objects such as drives.
In this way, objects are often built, or composed, from other objects: This is composition.

60. Has-a Relationships
While an inheritance relationship is considered an Is-a relationship for reasons already discussed, a composition relationship is termed a Has-a relationship.

61. Has-a Relationships
Using the example in the previous section, a television Has-a a tuner and Has-a video display.
A television is obviously not a tuner, so there is no inheritance relationship.

62. Has-a Relationships
In the same vein, a computer Has-a video card, Has-a keyboard, and Has-a disk drive.
The topics of inheritance, composition and how they relate to each other is covered in great detail later in the course.

63. How Java Works
See

64. Qu es ti ons? The End ______________________ Devon M. Simmonds
Computer Science Department
University of North Carolina Wilmington
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