What are abstract classes in Java?

What are abstract classes in Java?

Abstract classes in Java are classes that cannot be instantiated and can contain abstract methods that must be implemented by subclasses.

Can you give me an example of an abstract class?

Sure! Here's a simple example:

abstract class Animal {
    abstract void sound();
}

class Dog extends Animal {
    void sound() {
        System.out.println("Bark");
    }
}

What is the difference between an abstract class and an interface?

An abstract class can have both abstract and concrete methods, while an interface can only have abstract methods (until Java 8, which introduced default methods).

When should I use an abstract class instead of an interface?

Use an abstract class when you want to share code among closely related classes, and use an interface when you want to define a contract for classes that may not be related.