Choosing Between an Interface and an Abstract Class in Java

Using an Interface vs. Abstract Class in Java

When it comes to object-oriented programming in Java, an interface and an abstract class have different key features. This article explores the differences between an interface and an abstract class in Java.

Interfaces

An interface is a collection of static constants and abstract methods. It is like an abstract class but with a few differences. Interfaces can only contain abstract methods and static constants. They cannot contain any concrete code or constructor implementations. Interfaces are used to provide a common set of behaviour to all implementations of the interface. This enables multiple classes to share the same type of behaviour without having to be related to each other. An example of an interface would be Runnable, which allows classes to be executed in a thread.

Abstract Classes

An abstract class is similar to an interface, but it can also contain concrete code and constructors. The primary purpose of an abstract class is to provide a common base from which other classes can inherit. An abstract class can also allow for more flexibility when creating new classes. Unlike an interface, an abstract class can contain both abstract and concrete methods.

Which One Should I Use?

When deciding between using an interface or an abstract class, you should consider the following:

• If you want to ensure that a specific behavior is implemented by all your classes, then you should use an interface.
• If you want to have some concrete code that can be shared among all your classes, then you should use an abstract class.
• If you are just using a class as a way to group together related functionality, then you should use an interface.
• If you need to implement some common logic for all your classes, then you should use an abstract class.

It is important to note that you can use both an interface and an abstract class in the same project to achieve certain goals. Just remember that they have different purposes and use them accordingly.