What Is Abstraction In Object-Oriented Programming?

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This is a quick blog post on my understanding of abstraction. Abstraction is one of the key concepts of object-oriented programming.

It’s main purpose is to hide details, and only expose a high-level mechanism for using it. Implementation details should not be shown.

An example of abstraction, is an abstract class. An abstract class can contain abstract methods. This means a class extending from the abstract class, needs to implement the abstract methods. It isn’t concerned with how it is done, as long as the abstract methods are implemented.

I have a blog post on abstract classes, and interfaces here, but here’s a quick example, using an abstract class Phone and a concrete class, MobilePhone:

1public abstract class Phone {
2 public abstract void acceptIncomingCall();
3 public abstract void makeOutgoingCall();
4 public abstract void ring();
7public class MobilePhone extends Phone {
8 public void acceptIncomingCall(){
9 if(isRinging() & isPickupCallButtonPressed()){
10 answerCall();
11 }
12 }
14 public void makeOutgoingCall(){
15 if(!isRinging() & isPhoneNumberEntered()){
16 makeCall();
17 }
18 }
20 public void ring(){
21 System.out.println("Ring!");
22 }
24*// note: other **private **methods in MobilePhone are not shown - isRinging(), isPickupCallButtonPressed(), isPhoneNumberEntered(), answerCall(), methodCall()*

As demonstrated, MobilePhone has implemented the abstract methods from Phone.

Another demonstration of abstraction is shown in MobilePhone, where only the public methods, acceptIncomingCall(), makeOutgoingCall, and ring() are exposed to other classes (public).

All the other stuff under the hood is hidden and the following methods are private: isRinging(), isPickupCallButtonPressed(), isPhoneNumberEntered(), answerCall(), methodCall().

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