What are the best practices for using abstract classes in Java?

What are the best practices for using abstract classes in Java?

When using abstract classes in Java, it's important to ensure that they are used to define a common base for related classes. Here are some best practices:

1. Use abstract classes when you have shared code among subclasses.
2. Keep the abstract class focused on a specific purpose.
3. Avoid using abstract classes for unrelated classes.
4. Use abstract methods to enforce a contract for subclasses.

Can you give an example of when to use an abstract class?

Sure! For instance, if you have a class hierarchy for different types of vehicles, you might create an abstract class called Vehicle. This class could have common properties like speed and methods like startEngine(). Then, subclasses like Car and Truck can extend Vehicle and implement specific behaviors.

What about the difference between abstract classes and interfaces?

Great question! The main difference is that an abstract class can have both abstract methods and concrete methods (with implementation), while an interface can only have abstract methods (prior to Java 8) and default methods (from Java 8 onwards). Abstract classes are used when you want to share code among related classes, while interfaces are used to define a contract that multiple classes can implement.

Are there any performance considerations when using abstract classes?

Generally, the performance impact of using abstract classes is minimal. However, it's important to avoid deep inheritance hierarchies, as they can lead to increased complexity and potential performance issues. Always prioritize design clarity and maintainability over micro-optimizations.