Right now, you have gone through a very important process. If you feel comfortable with the previous lesson, you are ready to know more in the area of object-oriented programming.
The four main concepts are involved in OOP:
Abstraction involves interface definition and abstract class.
Encapsulation involves access control of member methods and fields with access modifiers like public, protected, private, etc.
Inheritance involves how extends and implements work.
Polymorphism means "many forms", involving variable passing, overloading, overriding, etc.
To grasp these concepts, you need to spend more time to learn and practise.
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