Key Differences Between Abstract Classes and Interfaces in OOP

1. What They Are:

   • Abstract Class: This is a type of class that you can't create objects from. It helps set up basic features that other classes can use.
   • Interface: Think of this like a set of rules. It tells a class what methods it should have but doesn't tell it how to do them.

2. How They Work:

   • Abstract Class: These can have methods (functions), fields (variables), and special methods called constructors.
   • Interface: They only list the methods without saying how to do them. Since Java 8, they can have some default methods that provide basic behavior.

3. Inheritance Rules:

   • Abstract Class: You can only inherit from one abstract class. This means one class can only extend one abstract class at a time.
   • Interface: You can inherit from many interfaces. This means one class can follow the rules of several interfaces.

4. When to Use Them:

   • Use abstract classes when you want to share certain behaviors across a group of classes.
   • Use interfaces when you want to create different classes that can do similar things in different ways.