The Java® Language Specification, Java SE 7 Edition, Fourth Edition

9.6. Annotation Types

An annotation type declaration is a special kind of interface declaration. To distinguish an annotation type declaration from an ordinary interface declaration, the keyword interface is preceded by an at-sign (@).

Note that the at-sign (@) and the keyword interface are two distinct tokens. Technically it is possible to separate them with whitespace, but this is discouraged as a matter of style.

AnnotationTypeDeclaration:    InterfaceModifiers_opt @ interface Identifier AnnotationTypeBodyAnnotationTypeBody:    { AnnotationTypeElementDeclarations_opt }AnnotationTypeElementDeclarations:    AnnotationTypeElementDeclaration    AnnotationTypeElementDeclarations AnnotationTypeElementDeclaration

If an annotation a (§9.7) on an annotation ...