Question

What are abstract classes (as opposed to concrete classes) and how are they useful? - The use of dynamic binding to apply polymorphic behavior - Only allowed when subclass is an object of a superclass (the is-a relationship is valid) - Can you instantiate abstract classes? - When should you use downcasting? - final methods and classes and using them with inheritance and polymorphism - Cannot override final methods - Understand what interfaces are and their uses in Java (makes Java extensible) - Unrelated classes have a set of common methods and design - Using implements keyword to indicate that a class implements an interface - Classes can have more than one interface (but only one superclass)

Answer 1

Abstract classes are classes that cannot be instantiated and are used as blueprints for other classes. They allow for common behaviors and attributes while still allowing each subclass to have its own implementation. Polymorphic behavior is achieved through dynamic binding.

Step-by-step explanation:

Abstract classes in Java are classes that cannot be instantiated, meaning you cannot create objects directly from them. They are designed to serve as blueprints for other classes, providing a common interface and partially implemented functionality. Concrete classes, on the other hand, can be instantiated and provide complete implementation for all their methods.

Abstract classes are useful when you want to define common behaviors and attributes for a group of related classes, while still allowing each subclass to have its own specific implementation details. By using abstract classes, you can enforce consistency and structure within a class hierarchy.

One key advantage of abstract classes is their ability to apply polymorphic behavior using dynamic binding. This means that an object of a subclass can be assigned to a reference variable of its superclass, allowing for flexibility and code reusability.