Default Methods in interfaces

What are default methods?

Before Java 8, we could only declare abstract methods in an interface. However, Java 8 introduced the concept of default methods. Default methods are methods that can have a body. The most important use of default methods in interfaces is to provide additional functionality to a given type without breaking down the implementing classes.

Before Java 8, if a new method was introduced in an interface then all the implementing classes used to break. We would need to provide the implementation of that method in all the implementing classes.

However, sometimes methods have only single implementation and there is no need to provide their implementation in each class. In that case, we can declare that method as a default in the interface and provide its implementation in the interface itself.

Syntax of default methods

Let’s understand the syntax of default methods through an example. Here, we have an interface with one abstract and one default method: