Abstract classes and interfaces in Java serve fundamentally different purposes. Learn the differences between these Java language elements and how to use them in your programs.

In this Java 101 tutorial, I’ve explained how interfaces differ from classes, and showed you how to declare, implement, and extend interfaces in your Java programs.

When you run the inner class example, the output would be nine. Java’s Function and lambda expression example. Of course, the whole idea of the functional interface is to incorporate lambda ...