Abstraction and Interface in Java

Abstraction:

--Abstraction is a process of hiding the implementation details and showing only functionality to the user.
--In Abstraction only the essential details are displayed to the user. The trivial or the non-essentials units are not displayed to the user. Ex: A car is viewed as a car rather than its individual.
--There are two ways to achieve abstraction in java
1. Abstract class (0 to 100%)
2. Interface (100%)

Abstract Class:

A class which is declared as abstract is known as an abstract class. It can have abstract and non-abstract methods. It needs to be extended and its method implemented.
An abstract class must be declared with an abstract keyword.
Abstract Class can have abstract and non-abstract methods.
Abstract class cannot be instantiated.
Abstract class can have constructors final and static methods also.
Abstract class can have final methods
If there is an abstract method in a class, that class must be abstract.

Interface:

--An interface in java is a blueprint of a class. It has static constants and abstract methods.
--There can be only abstract methods in the Java interface, not method body. It is used to achieve abstraction and multiple inheritance in Java.
--It cannot be instantiated just like the abstract class.
--In interface we can have default and static methods.
--In interface we can have private methods.

Class and Interface Relationships:

Class and Interface Relationships

Why we use Interface?

--It is used to achieve abstraction.
--By interface, we can support the functionality of multiple inheritance.

Multiple inheritance in Java by interface:

--If a class implements multiple interfaces, or an interface extends multiple interfaces, it is known as multiple inheritance.
--Multiple inheritance is not supported through class in java, but it is possible by an interface,

Abstract Class Vs Interface

Difference between Abstract Class and Interface

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