What's the difference between interface and @interface in java?

Question

I haven't touched Java since using JBuilder in the late 90's while at University, so I'm a little out of touch - at any rate I've been working on a small Java project this week, and using Intellij IDEA as my IDE, for a change of pace from my regular .Net development.

I notice it has support for adding interfaces and @interfaces, what is an @interface, and how does it differ from a normal interface?

public interface Test {
}

vs.

public @interface Test {
}

I've done a bit of searching, but couldn't find a great deal of useful info referring to @interface.

Answer 1

The @ symbol denotes an annotation type definition.

That means it is not really an interface, but rather a new annotation type -- to be used as a function modifier, such as @override.

See this javadocs entry on the subject.

Answer 2

The interface keyword indicates that you are declaring a traditional interface class in Java.

The @interface keyword is used to declare a new annotation type.

See Sun tutorial on annotations for a description of the syntax.

See the JLS if you really want to get in to the details of what @interface means.

Answer 3

I stopped using Java when c# was born

Annotation are just metadata for use in reflection etc

Just like attributes in c#