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

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Answered by suresh

Abstract Class vs Interface in OOP - Computer Science Interview Question

Abstract Class vs Interface in Object-Oriented Programming

Both abstract classes and interfaces are important concepts in object-oriented programming, but they serve different purposes:

Abstract Class:

An abstract class is a class that cannot be instantiated on its own and is meant to be used as a base class. It may contain both abstract methods (methods without a body) and concrete methods. Subclasses that inherit from an abstract class must implement the abstract methods. An abstract class can also have member variables and constructors.

Interface:

An interface is like a contract that defines a set of methods that a class must implement. It only contains method signatures without any implementations. A class can implement multiple interfaces, allowing for achieving multiple inheritance in Java. Interfaces are used to define a common behavior that can be implemented by different classes.

Key Differences:

  • An abstract class can have both abstract and concrete methods, while an interface can only have method signatures.
  • A class can inherit from only one abstract class, but it can implement multiple interfaces.
  • Abstract classes can have member variables, constructors, and methods with access modifiers, while interfaces cannot contain these.
  • Interfaces promote loose coupling and allow for a class to implement multiple behaviors, while abstract classes are used to define a base class for inheritance.

Understanding the differences between abstract classes and interfaces is crucial for designing flexible and maintainable object-oriented systems.

Answer for Question: Explain the difference between an abstract class and an interface in object-oriented programming.