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Introduction to �Object Oriented Programming�

Gayathri Namasivayam

Introduction to OOP

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Topics

  • Why use OOP?
  • Building blocks of OOP
    • Classes
    • Objects
  • What is OOP?
  • OOP concepts
    • Abstraction
    • Encapsulation
    • Inheritance
    • Polymorphism
  • Advantages vs Disadvantages
  • Conclusion

Introduction to OOP

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Topics

  • Why use OOP?
  • Building blocks of OOP
    • Classes
    • Objects
  • What is OOP?
  • OOP concepts
    • Abstraction
    • Encapsulation
    • Inheritance
    • Polymorphism
  • Advantages vs Disadvantages
  • Conclusion

Introduction to OOP

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Why use OOP?

  • Object Oriented Programming (OOP) is one of the most widely used programming paradigm

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  • Why is it extensively used?
    • Well suited for building trivial and complex applications
    • Allows re-use of code thereby increasing productivity
    • New features can be easily built into the existing code
    • Reduced production cost and maintenance cost

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  • Common programming languages used for OOP include C++, Java, and C#

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Topics

  • Why use OOP?
  • Building blocks of OOP
    • Classes
    • Objects
  • What is OOP?
  • OOP concepts
    • Abstraction
    • Encapsulation
    • Inheritance
    • Polymorphism
  • Advantages vs Disadvantages
  • Conclusion

Introduction to OOP

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Building Blocks of OOP: Objects & Classes

  • Object: models a
    • Real world object (ex. computer, book, box)
    • Concept (ex. meeting, interview)
    • Process (ex. sorting a stack of papers or comparing two computers to measure their performance)

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  • Class: prototype or blueprint from which objects are created

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Building Blocks of OOP: Objects & Classes

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  • Class has
    • Set of attributes or properties that describes every object
    • Set of behavior or actions that every object can perform

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  • Object has
    • Set of data (value for each of its attribute)
    • Set of actions that it can perform
    • An identity

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  • Every object belongs to a class

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Real World Example of Objects & Classes

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Introduction to OOP

Object: FordCar1

Behavior

Start, Accelerate, Reverse, Stop

Attributes

Color: Yellow

Type: Coupe

Model: Mustang

Cylinder: 6

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Attributes

Color, Type, Model, Cylinder

Behavior

Start, Accelerate, Reverse, Stop

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Class: FordCar

Behavior

Start, Accelerate, Reverse, Stop

Attributes

Color: Orange

Type: Coupe

Model: Focus

Cylinder: 4

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Object: FordCar2

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Another Real World Example..

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Introduction to OOP

Attributes

Name, Height, Age

Behavior

Speak, Listen, Eat, Run, Walk

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Class: Person

Object: Person1

Attributes

Name: Ann

Height: 5’ 4”

Age: 21

Behavior

Speak, Listen, Eat, Run, Walk

Attributes

Name: Adam

Height: 5’ 9”

Age: 24

Behavior

Speak, Listen, Eat, Run, Walk

Object: Person2

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Class

  • A class is a set of variables (to represent its attributes) and functions (to describe its behavior) that act on its variables

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Class ShippingBox

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Introduction to OOP

int shipping_cost() {

return cost_per_pound*weight;

}

sender_name : string

receiver_name : string

cost_per_pound : int

weight : int

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shipping_cost() : int

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Object

  • Object is an instance of a class that holds data (values) in its variables. Data can be accessed by its functions

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Objects of ShippingBox class

Introduction to OOP

sender_name = Jim

receiver_name = John

cost_per_pound = 5

weight = 10

shipping_cost()

Object BoxB

Object BoxA

sender_name = Julie

receiver_name = Jill

cost_per_pound = 2

weight = 5

shipping_cost()

Class ShippingBox

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Topics

  • Why use OOP?
  • Building blocks of OOP
    • Classes
    • Objects
  • What is OOP?
  • OOP concepts
    • Abstraction
    • Encapsulation
    • Inheritance
    • Polymorphism
  • Advantages vs Disadvantages
  • Conclusion

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What is OOP?

  • Paradigm for problem solving by interaction among objects
  • It follows a natural way of solving problems

    • Ex. Ann wants to start her car

(1) Ann walks to her car

(2) Ann sends a message to the car to start by turning on the ignition

(3)The car starts

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Problem Solving in OOP

Problem: Ann wants to start her car

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Introduction to OOP

Name = Ann

Age = 21

Speak()

Run()

Walk()

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Object Ann

Color = Yellow

Type = Coupe

Model = Mustang

Cylinder = 6

Start()

Accelerate()

Stop()

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Object Ann’s car

message

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Topics

  • Why use OOP?
  • Building blocks of OOP
    • Classes
    • Objects
  • What is OOP?
  • OOP concepts
    • Abstraction
    • Encapsulation
    • Inheritance
    • Polymorphism
  • Advantages vs Disadvantages
  • Conclusion

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Abstraction

Introduction to OOP

  • Extracting essential properties and behavior of an entity
  • Class represents such an abstraction and is commonly referred to as an abstract data type

Ex. In an application that computes the shipping cost of a box, we extract its properties: cost_per_pound, weight and its behavior: shipping_cost()

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Abstraction

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Introduction to OOP

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sender_name : string

receiver_name : string

cost_per_pound : int

weight : int

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shipping_cost() : int

Class

Shipping Box

Attributes

Sender’s name,

Receiver’s name,

Cost of shipping per pound,

Weight

Behavior

Calculate shipping cost

Abstraction

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Topics

  • Why use OOP?
  • Building blocks of OOP
    • Classes
    • Objects
  • What is OOP?
  • OOP concepts
    • Abstraction
    • Encapsulation
    • Inheritance
    • Polymorphism
  • Advantages vs Disadvantages
  • Conclusion

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Encapsulation

Introduction to OOP

sender_name

receiver_name

cost_per_pound

weight

shipping_cost()

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  • Mechanism by which we combine data and the functions that manipulate the data into one unit
  • Objects & Classes enforce encapsulation

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Topics

  • Why use OOP?
  • Building blocks of OOP
    • Classes
    • Objects
  • What is OOP?
  • OOP concepts
    • Abstraction
    • Encapsulation
    • Inheritance
    • Polymorphism
  • Advantages vs Disadvantages
  • Conclusion

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Inheritance

  • Create new classes (derived classes) from existing classes (base classes)
  • The derived class inherits the variables and functions of the base class and adds additional ones!
  • Provides the ability to re-use existing code

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Inheritance Example

BankAccount CheckingAccount SavingsAccount

Introduction to OOP

customer_name : string

account_type : string

balance : int

insufficient_funds_fee : int

deposit() : int

withdrawal() : int

process_deposit() : int

customer_name : string

account_type : string

balance : int

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deposit() : int

withdrawal() : int

customer_name : string

account_type : string

balance : int

interest_rate : int

deposit() : int

withdrawal() : int

calculate_interest() : int

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Inheritance Example

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Introduction to OOP

interest_rate : int

calculate_interest() : int

insufficient_funds_fee : int

process_deposit() : int

CheckingAccount

SavingsAccount

customer_name : string

account_type : string

balance : int

deposit() : int

withdrawal() : int

BankAccount

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Topics

  • Why use OOP?
  • Building blocks of OOP
    • Classes
    • Objects
  • What is OOP?
  • OOP concepts
    • Abstraction
    • Encapsulation
    • Inheritance
    • Polymorphism*
  • Advantages vs Disadvantages
  • Conclusion

(* To be covered in the next class)

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Disadvantages of OOP

  • Initial extra effort needed in accurately modeling the classes and sub-classes for a problem
  • Suited for modeling certain real world problems as opposed to some others

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Conclusion

  • Classes & Objects
  • Concepts in OOP
    • Abstraction
    • Encapsulation
    • Inheritance
  • Advantages & Disadvantages
  • Next class
    • Be prepared for an in-class activity (based on topics covered today)!
    • Polymorphism in OOP!

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Thank you!

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Introduction to OOP