The Difference between Abstract Class and Interface in Java

Abstract Class vs. Interface: One key difference between abstract classes and interfaces in Java is that abstract classes can have both abstract and non-abstract methods, while interfaces can only have abstract methods, which are implicitly public and abstract. Additionally, a class can extend only one abstract class but implement multiple interfaces.

When to Use Abstract Class: Abstract classes are useful when you want to provide a common implementation for a group of related classes, or if you need to define some concrete behavior along with abstract methods. Use an abstract class when you have a "is-a" relationship between objects that will inherit from it.

When to Use Interface: Interfaces are beneficial when you want to define a contract that specifies a set of methods that a class must implement. Use an interface when you need to achieve multiple inheritances, as a class can implement multiple interfaces. Interfaces are also useful for defining a common behavior across unrelated classes.

Overall, the decision to use an abstract class or an interface in a project depends on the specific requirements and design considerations of the application. Understanding the differences between the two and their respective use cases is essential for making the right choice.