[PDF] abstract class extends abstract class

An abstract class can extend another abstract class. And any concrete subclasses must ensure that all abstract methods are implemented. Abstract classes can themselves have concrete implementations of methods. These methods are inherited just like a method in a non-abstract class.
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  • Can abstract class implement abstract class?

    An abstract method doesn't have any implementation (method body). A class containing abstract methods should also be abstract. We cannot create objects of an abstract class. To implement features of an abstract class, we inherit subclasses from it and create objects of the subclass.

  • Can abstract classes extend each other?

    A class can implement multiple interfaces. A class can extend only one abstract class.

  • When a class extends an abstract class?

    Any class that extends a class with an abstract method must implement that method. For example, our Mammal class includes an abstract speak() method. Any class that extends Mammal must implement the speak method, and that implementation must have the same signature.
  • I earlier learned that abstract class can extend concrete class. Though I don't see the reason for it from JAVA designers, but it is ok. I also learned that abstract class that extends concrete class can make overriden methods abstract.
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