Abstract Classes vs Interfaces in Java

Abstract classes and interfaces are two key concepts in Java programming, each serving a different purpose.

Difference Between Abstract Classes and Interfaces:

• Abstract classes:
  • Can have both abstract (incomplete) and concrete (complete) methods
  • Can have member variables
  • Can have constructors
  • Can be extended using the "extends" keyword
• Interfaces:
  • Can only have abstract methods (methods without implementation)
  • Cannot have member variables (except constants)
  • Cannot have constructors
  • Can be implemented by classes using the "implements" keyword

When to Use Abstract Classes and Interfaces:

Use abstract classes when you want to provide a common base implementation for subclasses, and when you want to define some methods as abstract and force subclasses to implement them.

Use interfaces when you want to define a contract for classes to implement, without providing any implementation details. This allows for multiple inheritance, as a class can implement multiple interfaces.

Both abstract classes and interfaces are important tools in Java programming and should be used based on the specific requirements of your project.