Java  abstraction class and programming example

Ø  Inheritance 1.       IS-A relationship 2.        (HAS-A   relationship) Ø  Polymorphism 1.       Method overloading 2.       Method overriding

1.       Abstraction 2.       Data hiding 3.       Encapsulation 4.       Tightly coupled class

 

Abstract class:- abstraction is a hiding internal implementation and just highlighting the setup that we are offering.

Q.1  don’t get confused between abstraction and encapsulation?

Abstraction	Encapsulation
Abstraction is a detail hiding(implementation hiding)	Encapsulation  is a data hiding (information hiding)
Data abstraction deals with exposing the interface to the user and hiding details of implementation.	Encapsulation groups together data methods that act upon the data.

 

Abstraction is two there are described below:-

1.       Using abstract class (0 to 100%  security)

2.       Using interface class (100%  security)

Ø  A method without the body (no implementation ) is known as an abstract method.

Ø  A method must always be declared in an abstraction class. Or  We can say that if a class has an abstract method, it should be declared abstract as well.

Ø  If a regular class extends an abstraction class .when the class must have to implement all the abstract methods of the abstract parent class or it has to be declared abstract as well.

Ø  Abstract methods in an abstract class are meant to be overridden in derived concrete classes otherwise a compile-time error will be thrown.

Ø  Abstraction classes cannot be instantiated, means we can’t create an object of abstract class.

Example:-

abstract class Vehicle  {
abstract void start();    {

class  Car extends  Vehicle     {
void start()   {

System.out.println(“car   start with key”);

}

}

class  Scoter extends  Vehicle    {

void start()   {
System.out.println(“car   start with key”);

}

public static void main(String  args[])    {

Car   c= new Car();

c.start();

Scoter s= new  Scoter ();

s.start();

}

}