The annotations @GET, @POST, @PUT etc are all of the @HttpMethod annotation type, for example @GET:
and the API of @HttpMethod clearly states that:
Annotation Type HttpMethod Associates the name of a HTTP method with an annotation. A Java method annotated with a runtime annotation that is itself annotated with this annotation will be used to handle HTTP requests of the indicated HTTP method. It is an error for a method to be annotated with more than one annotation that is annotated with HttpMethod.