update

src/java/lodge/reservationsystem/CabinReservation.java

@@ -3,7 +3,7 @@ package lodge.reservationsystem;
 import java.time.ZonedDateTime;
 import java.time.temporal.ChronoUnit;
 
-public final class CabinReservation extends Reservation{
+public final class CabinReservation extends Reservation implements IReservation{
 
   CabinReservation(){
     super();

src/java/lodge/reservationsystem/HotelReservation.java

@@ -3,7 +3,7 @@ package lodge.reservationsystem;
 import java.time.ZonedDateTime;
 import java.time.temporal.ChronoUnit;
 
-public final class HotelReservation extends Reservation {
+public final class HotelReservation extends Reservation implements IReservation {
 
   HotelReservation() {
     super();

src/java/lodge/reservationsystem/HouseReservation.java

@@ -3,7 +3,7 @@ package lodge.reservationsystem;
 import java.time.ZonedDateTime;
 import java.time.temporal.ChronoUnit;
 
-public final class HouseReservation extends Reservation {
+public final class HouseReservation extends Reservation implements IReservation{
 
   HouseReservation(){
     super();

src/java/lodge/reservationsystem/IReservation.java

@@ -1,9 +1,5 @@
 package lodge.reservationsystem;
 
 public interface IReservation {
-    
-    public String ReservationType();
-    public boolean checkValid() throws ReservationException;
-    public float calculatePrice();
 
 }

src/java/lodge/reservationsystem/Reservation.java

@@ -8,7 +8,7 @@ import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.time.ZonedDateTime;
 
-public abstract class Reservation implements IReservation{
+public abstract class Reservation{
     private char type;
     private String reservation_number = "-99";
     private Address physical_address;
@@ -244,4 +244,9 @@ public abstract class Reservation implements IReservation{
 
     }
 
+    
+    public abstract String ReservationType();
+    public abstract boolean checkValid() throws ReservationException;
+    public abstract float calculatePrice();
+
 }