Is an interface a class?

Question

Is an interface a special kind of class or can you say that an interface isn\'t a class at all?

Answer 1

An interface isn't a class, but you could say that both interfaces and classes are types.

From the Java specification:

In the Java programming language, every variable and every expression has a type that can be determined at compile-time. The type may be a primitive type or a reference type. Reference types include class types and interface types.

Notice though there is a special class called Class that can represent both classes and interfaces:

Instances of the class Class represent classes and interfaces in a running Java application.

The fact that an interface is represented by a Class instance where isInterface is true could give you the impression that an interface is just a special type of class. However this is not the case.