Any class that contains one or more abstract methods is known as abstract class. A class can be declared abstract using the “abstract” keyword followed by class declaration. A class declared abstract may or may not include abstract methods. An abstract class can have abstract methods(methods without implementation) as well as concrete methods (methods with implementation). A normal class(non abstract class) is not allowed to have abstract methods.

An abstract class can not be instantiated, which means you are not allowed to create an object of it. Abstract classes can only be extended; and the subclass must provide implementations for all of the abstract methods in its parent class. If a subclass does not implements abstract methods, then the subclass must also be declared abstract.

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