Describe the difference between an abstract class and an interface in object-oriented programming.

Abstract Class vs Interface in Object-Oriented Programming

When it comes to object-oriented programming, understanding the difference between an abstract class and an interface is crucial. Both serve as blueprints for classes to implement common behaviors, but they have distinct characteristics that set them apart.

Abstract Class:

• An abstract class is a class that cannot be instantiated on its own and may contain both abstract and non-abstract methods.
• It can have constructors, instance variables, and methods with varying levels of access modifiers.
• Subclasses must implement all the abstract methods defined in an abstract class.
• It allows for code reusability through inheritance.

Interface:

• An interface is a reference type in Java that contains only method signatures and constants.
• It cannot have method definitions or instance variables, only abstract methods.
• A class can implement multiple interfaces, enabling polymorphic behavior.
• Interfaces promote loose coupling and allow for achieving multiple inheritance in Java.

In summary, an abstract class provides a partial implementation of a class and allows for code sharing through inheritance, while an interface defines a contract for classes to follow without providing any implementation. Both are essential tools in object-oriented programming, each serving different purposes based on the design requirements of the system.