Abstraction in OOPS | How Abstraction can be achieved in JAVA

Abstraction:

We all know that abstraction is one of the characteristics of Object Oriented Programming System (OOPS). If you ask someone "what is abstraction?" the most common possible answer that you hear is .. "Abstraction is hiding some important features or data ..bla ..bla..bla "

The question is ..what is hiding ..? where you are hiding..? which part you are hiding ..?

Is hiding something is the correct definition for abstraction ?

then what it (abstraction) really means?

Here it goes:

In simple words i can say.. "Abstraction implies providing something.. but not everything"

i will consider one real time example to illustrate it in much better way.

Suppose there is an aeroplane flying in the sky. We know that it is flying, but we don't know how exactly it is flying and what are the underlying mechanisms, working and all. 

this is what we are looking for.. "abstraction"

How to achieve Abstraction in Java:

By using abstract classes or interfaces , we can achieve abstraction in Java.

As we all know that abstract classes, interfaces contains abstract methods (ofcourse abstract classes may or may not contain) i.e , only method declarations.

By looking at the method declaration we can estimate what exactly the method is doing, what it is going to return. But we don't know how exactly the abstract method will be implemented.

We came to know about the implementation, once we provided the method implementation in the classes which implement the corresponding abstract class or interface.

Example for the above illustration:

Let us consider an interface ( you can take abstract class also) Addicted.

In the above interface, getAddictedListOfPersons() is the abstract method (by default all the methods in an interface are public abstract ) which returns list of all the addicted persons. By looking at the method declaration we can infer this.

(As per the java documentation we should give proper names to the methods and variables)

But we don't know how exactly the method will be implemented in it's (interface) implementation classes.

Following are the implementation classes for the interface Addicted.

The class AddictedToJava is providing implementation to the abstract method which returns the list of persons who were addicted to Java.

The class AddictedToAndroid is providing implementation to the abstract method which returns the list of persons who were addicted to Android.

Now , by looking at these implementations we came to know that the implementation is different in both of the implementation classes for the interface(Addicted).

Only after providing implementation, we came to know how exactly the method was implemented.

This is considered to be abstraction what i mentioned in the begining of the article.

Abstraction ------> Providing something.. but not everything