What is abstract class? What is interface? Difference between both and when do we use them?

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Abstract class is a class that cannot be instantiated and may contain abstract methods. Interface is a contract that defines methods that a class must implement.

Abstract class can have both abstract and non-abstract methods, while interface can only have abstract methods.
A class can inherit only one abstract class but can implement multiple interfaces.
Abstract classes are used when you want to provide a default implementation for some methods, while interfaces are used to define a contract for classes to implement.
Example: Abstract class - Animal with abstract method 'eat'. Interface - IShape with method 'calculateArea'.

What is abstract class? What is interface? Difference between both and when do we use them?

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