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ABSTRACTION IN JAVA

Abstraction is process that hide implementation details and show only functionality to users.

What is Abstraction in Java?

 
In this blog, we show what is abstract in java. so lets start from 

What Is Abstraction in java?
Abstraction is process that hide implementation details and show only functionality to users.
In another words, It shows only essential things to user and hide the internal details.
Like, you search on google and find your content but what happen internally you does not care.

So we learn about Abstract class and Method in Java.

Abstract Class In Java
Abstract class means that are declared with abstract keyword before class. 
So if we declare abstract keyword in class then we does not instantiate that class. means we can not create of abstract class...
So you asked then how we use abstract classes member data?
We can create subclass from abstract class and create object of subclass to access abstract class member data.

abstract class AbstractDemo {
    // Class members
}

So before jump into coding lets see key point of abstract
  • Abstract class must be declared with abstract keyword.
  • Abstract class can not be instantiated (can not create object of it).
  • Abstract class contains abstract as well as non abstract methods also.
  • Abstract class also contains constructors and static methods.
abstract class AbstarctDemo{
//Abstract Method
abstract void abstractMethod(); 
  
// Non Abstract method
void nonAbstractMethod() {
System.out.println("Non Abstract Method");
} 
}  

class Demo extends AbstarctDemo{  

void abstractMethod() {
System.out.println("Abstract Method from AbstractDemo");
}  
public static void main(String args[]){  
AbstarctDemo obj = new Demo();  
obj.abstractMethod(); 
obj.nonAbstractMethod();
}
}  

In above example we declare Abstract class with abstract keyword and add two new method in which one is abstract and another is non abstract.

In above example if we create AbstractDemo object = new AbstractDemo() then we get error 'Cannot instantiate the type AbstarctDemo' .

Abstract Method in Java
Abstract method means declare with abstract keyword.
Abstract method can only declare in abstract class and it does not contain body. 
Body are provided in subclass who inherited from abstract class as we seen above example.

Follow Another simple example of abstract class and method.

abstract class Bank{    
abstract int getRateOfInterest();    
}    
class HDFCBank extends Bank{    
int getRateOfInterest()
{
return 4;
}    
}    
class AxisBank extends Bank{    
int getRateOfInterest()
{
return 5;
}    
}    
    
class ImplementBankInterest{    
public static void main(String args[]){   
Bank bankObj;  
bankObj = new HDFCBank();  
System.out.println("Rate of Interest is: "
                        + bankObj.getRateOfInterest()+" %");    
bankObj = new AxisBank();
System.out.println("Rate of Interest is: "
                        + bankObj.getRateOfInterest()+" %");    
}
} 


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