import java.util.List;

final class HandshakeCalculator {

    List<Signal> calculateHandshake(int number) {
        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
    }

}

@@ -21,14 +21,8 @@
 t;%0A%0A
-final 
 clas

remove final from class declaration in secret-handshake exercise