OOP Lecture #01

1. Object Oriented Programming in Java

2.  OOP is a programming paradigm
 What is programming paradigm
 A method or way to write a computer program for real world applications.
 Is there any other programming paradigm exists
 Yes
 Which one?
 Structure programming
 Functional programming
 Procedural programming
 Logical programming

3.  Code Reusability
 Practical approach
 Code maintenance
 Security
 Design benefits
 Better productivity
 Modularity

4.  Classes
 Objects & methods
 Inheritance
 Polymorphism
 Abstraction
 Encapsulation
Mastering these concepts means you are going to become an expert programmer in
industry soon.

5.  To understand OOP concepts relate them with real world.
 Whatever you do in your real world is actually one of the OOP concept.

6.  Smalltalk is first and purely OOP language.
 JAVA, C#, C++, Python etc these all are OOP languages.

7.  In real world class means a presentation for the group of some related objects like
 Animals class
 Birds class
 Vehicles class
 Human class, etc.
 For example if we talk about animal class than which objects should fall in this class
 Dog
 Cat
 Horse
 Tiger, etc.

8.  For example in bird class objects should be
 Sparrow
 Peacock
 Parrot
 Owl, etc.
 A class represents some methods/activities that the objects of that class follow, for
example
 Animals can (eat, run, walk, drink, fight, etc)
 Birds can (fly, eat, walk, drink, etc)
 Humans can (eat, run, walk, drink, fight, read, etc)

9.  Class is the collection of objects.
 Class is not the real world entity, it is just the template or blueprint.*
 Class does not occupy memory.**

10. access-modifiers class ClassName
{
Class body (methods, constructors, fields, blocks, nested class);
}
 In case of no access-modifier will written the default access modifier will be
considered.

11.  Method is a set of code which perform a particular task.
 Example eat(), run(), walk(), etc.
 Advantages of methods:
 Code reusability
 Code Optimization

12. access-modifier return-type methodName (list of parameters)
{
Method body(conditional, switch, control statements, variables etc)
}
If no access-modifier place the default modifier will take place in java.

13.  Object is an instance of class e.g. dog is an instance of animal.
 Object is real world entity.
 Object occupies memory.

14.  Identity: name
 State/Attribute: Breed, Age, Color
 Behaviors: Eat(), Run(), Bark()

15.  There are five ways to create object in java
 By using new keywords
 By using newInstance() method
 By using clone() method
 By using deserialization
 Mainly objects created by using new keyword.

16.  Declaration
 Declare variable that represent the object name. For example
 Animal buzo;
 Instantiation and Initialization (Initialization perform by using class name constructor.
 )
 buzo = new Animal();
 By combining declaration, instantiation and initialization the object can be create using
following syntax.
 Animal buzo = new Animal();

17.  The behavior/method of object call by using dot (.) operator.
 For example
 buzo.run()
 buzo.eat()
How to change the state/attribute of an object?
 The state/attribute of object can also be change by using dot(.) operator.
 For example
 buzo.color = black;
 buzo.age=3;

18. public class Animal
{
Int age = 1;
String breed = “GS”;
public void eat()
{
System.out.println(“I am eating”);
}
public void run()
{
System.out.println(“I am running”);
}
}
public static void main (String args[])
{
Animal dog = new Animal();
System.out.println(dog.age);
System.out.println(dog.breed);
dog.run();
dog.eat();
}