The Java Language Specification, Third Edition

INTERFACES Predefined Annotation Types 9.6.1
The following annotation type declaration provides default values for two of its four elements:
// Annotation type declaration with defaults on some elements
public @interface RequestForEnhancement {
int id(); // No default - must be specified in
// each annotation
String synopsis(); // No default - must be specified in
// each annotation
String engineer() default "[unassigned]";
String date() default "[unimplemented]";
}
The following annotation type declaration shows a Class annotation whose value is
restricted by a bounded wildcard.
// Annotation type declaration with bounded wildcard to
// restrict Class annotation
// The annotation type declaration below presumes the existence
// of this interface, which describes a formatter for Java
// programming language source code
public interface Formatter { ... }
// Designates a formatter to pretty-print the annotated class.
public @interface PrettyPrinter {
Class