I did try and build your code to run the test (I've no idea where the CsvParam and DateParam classes come from) but I think that the following will give you what you want without throwing the exception.

  @DELETE
  @Path("{uid: [0-9]+}")
  public Response deleteStudent(@PathParam("uid") int uid) {
    final Student deletedStudent = STUDENTS.remove(uid);

    if (deletedStudent == null) {
      return Response.status(Response.Status.NOT_FOUND).build();
    } else {
      return Response.ok().entity(true).build();
    }
  }