OOPS Basics

Object Oriented Programming Style

Agenda

  • What is OOPS ?

  • Classes

  • Objects

  • Constructors

  • this keyword

  • Real life example

What is OOPS?

Object Oriented Programming Style (OOPS) is a programming style that deals with classes & objects.

The main aim of object-oriented programming is to implement real-world entities, for example, object, classes, abstraction, inheritance, polymorphism, etc.

A class is a blueprint for the object.

What is a class ?

What is an object ?

What is a class ?

An object is an entity that has a state and some behaviour.

Car

Car

Blueprint

Blueprint

Blueprint

Factory

Blueprint

Factory

Blueprint

Blueprint

Blueprint

Properties:

Blueprint

Properties:

- Model name

Blueprint

Properties:

- Model name

- Color

Blueprint

Properties:

- Model name

- Color

- Price

Blueprint

Properties:

- Model name

- Color

- Price

 

Functionalities:

 

Blueprint

Properties:

- Model name

- Color

- Price

 

Functionalities:

- Drive

Blueprint

Properties:

- Model name

- Color

- Price

 

Functionalities:

- Drive

- Lock/Unlock

Properties:

- Model name

- Color

- Price

 

Functionalities:

- Drive

- Lock/Unlock

Properties:

- Model name

- Color

- Price

 

Functionalities:

- Drive

- Lock/Unlock

class Car {
    
}

Properties:

- Model name

- Color

- Price

 

Functionalities:

- Drive

- Lock/Unlock

class Car {

}

String

String

int

Properties:

- Model name

- Color

- Price

 

Functionalities:

- Drive

- Lock/Unlock

class Car {
     String model;
     String color;
     int price;
}

String

String

int

Properties:

- Model name

- Color

- Price

 

Functionalities:

- Drive

- Lock/Unlock

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;
}

String

String

int

Properties:

- Model name

- Color

- Price

 

Functionalities:

- Drive

- Lock/Unlock

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }
}

String

String

int

Properties:

- Model name

- Color

- Price

 

Functionalities:

- Drive

- Lock/Unlock

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

String

String

int

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}
class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}
class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

Blueprint

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

Blueprint

class Main {
    public static void main(String[] args) {


    }
}
class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

Blueprint

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        
    }
}
class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

Blueprint

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        
    }
}

c1

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

Blueprint

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        Car c2 = new Car();
        
    }
}

c1

c2

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

Blueprint

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        Car c2 = new Car();

//        Reading the properties
        System.out.println(c1.color);	// Black

    }
}

c1

c2

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

Blueprint

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        Car c2 = new Car();

//        Reading the properties
        System.out.println(c1.color);   // Black
        System.out.println(c1.model);   // Hatchback
        System.out.println(c1.price);   // 100000

    }
}

c1

c2

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        Car c2 = new Car();

//        Reading the properties
        System.out.println(c1.color);   // Black
        System.out.println(c1.model);   // Hatchback
        System.out.println(c1.price);   // 100000

    }
}
class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        Car c2 = new Car();

//        Reading the properties
        System.out.println(c1.color);   // Black
        System.out.println(c1.model);   // Hatchback
        System.out.println(c1.price);   // 100000

    }
}

class Car

model

color

price

Properties

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        Car c2 = new Car();

//        Reading the properties
        System.out.println(c1.color);   // Black
        System.out.println(c1.model);   // Hatchback
        System.out.println(c1.price);   // 100000

    }
}

class Car

model

color

price

Data members

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        Car c2 = new Car();

//        Reading the properties
        System.out.println(c1.color);   // Black
        System.out.println(c1.model);   // Hatchback
        System.out.println(c1.price);   // 100000

    }
}

class Car

model

color

price

drive()

lock()

unlock()

Data members

Functions

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        Car c2 = new Car();

//        Reading the properties
        System.out.println(c1.color);   // Black
        System.out.println(c1.model);   // Hatchback
        System.out.println(c1.price);   // 100000

    }
}

class Car

model

color

price

drive()

lock()

unlock()

Data members

Class methods

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        Car c2 = new Car();

//        Reading the properties
        System.out.println(c1.color);   // Black
        System.out.println(c1.model);   // Hatchback
        System.out.println(c1.price);   // 100000

    }
}

class Car

model

color

price

drive()

lock()

unlock()

Data members

Class methods

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        Car c2 = new Car();

//        Reading the properties
        System.out.println(c1.color);   // Black
        System.out.println(c1.model);   // Hatchback
        System.out.println(c1.price);   // 100000

    }
}

class Car

model

color

price

drive()

lock()

unlock()

Data members

Class methods

model:

color:

price:

Hatchback

Black

100000

c1

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        Car c2 = new Car();

//        Reading the properties
        System.out.println(c1.color);   // Black
        System.out.println(c1.model);   // Hatchback
        System.out.println(c1.price);   // 100000

    }
}

class Car

model

color

price

drive()

lock()

unlock()

Data members

Class methods

model:

color:

price:

Hatchback

Black

100000

c1

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        Car c2 = new Car();

//        Reading the properties
        System.out.println(c1.color);   // Black
        System.out.println(c1.model);   // Hatchback
        System.out.println(c1.price);   // 100000

    }
}

class Car

model

color

price

drive()

lock()

unlock()

Data members

Class methods

model:

color:

price:

Hatchback

Black

100000

c1

c2

model:

color:

price:

Hatchback

Black

100000

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        Car c2 = new Car();

//        Reading the properties
        System.out.println(c1.color);   // Black
        System.out.println(c1.model);   // Hatchback
        System.out.println(c1.price);   // 100000

    }
}

class Car

model

color

price

drive()

lock()

unlock()

Data members

Class methods

model:

color:

price:

Hatchback

Black

100000

c1

c2

model:

color:

price:

Hatchback

Black

100000

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        Car c2 = new Car();

//        Reading the properties
        System.out.println(c1.color);   // Black
        System.out.println(c1.model);   // Hatchback
        System.out.println(c1.price);   // 100000

    }
}

class Car

model

color

price

drive()

lock()

unlock()

Data members

Class methods

model:

color:

price:

Hatchback

Black

100000

c1

c2

model:

color:

price:

Hatchback

Black

100000

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        Car c2 = new Car();

//        Reading the properties
        System.out.println(c1.color);   // Black
        System.out.println(c1.model);   // Hatchback
        System.out.println(c1.price);   // 100000

        c2.color = "Gray";
        System.out.println(c2.color);	// Gray
    }
}

class Car

model

color

price

drive()

lock()

unlock()

Data members

Class methods

model:

color:

price:

Hatchback

Black

100000

c1

c2

model:

color:

price:

Hatchback

Black

100000

class Car {
    String model = "Hatchback";
    String color = "Black";
    int price = 100000;

    void drive() {
        System.out.println("Zoom zoom zoom");
    }

    void lock() {
        System.out.println("Car is now locked");
    }

    void unlock() {
        System.out.println("Car is now unlocked");
    }
}

class Main {
    public static void main(String[] args) {
        Car c1 = new Car();
        Car c2 = new Car();

//        Reading the properties
        System.out.println(c1.color);   // Black
        System.out.println(c1.model);   // Hatchback
        System.out.println(c1.price);   // 100000

        c2.color = "Gray";
        System.out.println(c2.color);	// Gray
    }
}

class Car

model

color

price

drive()

lock()

unlock()

Data members

Class methods

model:

color:

price:

Hatchback

Black

100000

c1

c2

model:

color:

price:

Hatchback

Gray

100000

A Java constructor is special method that is called when an object is instantiated.

It has the same name as the class itself and is invoked automatically at the time of object construction.

Constructors

Example: Complex Numbers

Write a class to store and perform operations on complex numbers.

In Java, this keyword is used to refer to the current object inside a  class method.

this keyword

class ComplexNumber {
    int real;
    int imaginary;

    //    Constructor
    ComplexNumber(int real, int imaginary) {
        this.real = real;
        this.imaginary = imaginary;
    }
}
Made with Slides.com