improve specification and code for some methods

src/main/java/fr/univnantes/trainreservation/TicketReservationSystem.java

@@ -97,6 +97,9 @@ public interface TicketReservationSystem {
      * - The origin must be different from the destination.
      * @return The created registered trip.
      * @throws TripException If one of the above constraints was not satisfied.
+     * @throws NullPointerException if one of the parameters is null
+     * @throws IllegalArgumentException if the provided City or Train objets are not part of the TicketReservationSystem
+     * 
      */
     Trip createTrip(City origin, City destination, Train train, Instant departure, Instant arrival) throws TripException;
 
@@ -109,7 +112,7 @@ public interface TicketReservationSystem {
 
     /**
      * Adds a departure delay to a trip.
-     * Also automatically adds an arrival delay of the same amount.
+     * Also automatically adds an arrival delay of the same amount (see 'delayTripArrival').
      * @param delay The amount of delay to add.
      */
     void delayTripDeparture(Trip trip, Duration delay);
@@ -122,22 +125,24 @@ public interface TicketReservationSystem {
     void delayTripArrival(Trip trip, Duration delay);
 
     /**
-     * Finds the trip that follows an existing trip of a train.
+     * Finds the trip that follows an existing trip of a train, if it exists.
      * @param train The train.
-     * @param trip The trip.
-     * @return The trip following the given trip, for the train.
-     * @throws TripException if the trip's train is not the same
+     * @param trip The given trip.
+     * @return The train trip following the given trip, or an empty result if the given trip is the last.
+     * @throws IllegalArgumentException if the given train or trip are part of the TicketReservationSystem, or if the given trip is not linked with the given train.
+     * @throws NullPointerException if train or trip is null
      */
-    Optional<Trip> findNextTripOfTrain(Train train, Trip trip) throws TripException;
+    Optional<Trip> findNextTripOfTrain(Train train, Trip trip) throws IllegalArgumentException, NullPointerException;
 
     /**
-     * Finds the trip that precedes an existing trip of a train.
+     * Finds the trip that precedes an existing trip of a train, if it exists.
      * @param train The train.
      * @param trip The trip.
-     * @return The trip preceding the given trip, for the train.
-     * @throws TripException if the trip's train is not the same
+     * @return The train trip preceding the given trip, or an empty result if the given trip is the first.
+     * @throws IllegalArgumentException if the given train or trip are not part of the TicketReservationSystem, or if the given trip is not linked with the given train.
+     * @throws NullPointerException if train or trip is null
      */
-    Optional<Trip> findPreviousTripOfTrain(Train train, Trip trip) throws TripException;
+    Optional<Trip> findPreviousTripOfTrain(Train train, Trip trip) throws IllegalArgumentException, NullPointerException;
 
     /**
      * Finds and orders all the trips of a given train.

src/main/java/fr/univnantes/trainreservation/impl/TicketReservationSystemImpl.java

@@ -86,8 +86,22 @@ public class TicketReservationSystemImpl implements TicketReservationSystem {
 
     @Override
     public Trip createTrip(City origin, City destination, Train train, Instant departure, Instant arrival) throws TripException {
-        List<Trip> trainTrips = this.findOrderedTripsOfTrain(train);
 
+        Objects.requireNonNull(origin);
+        Objects.requireNonNull(destination);
+        Objects.requireNonNull(train);
+        Objects.requireNonNull(departure);
+        Objects.requireNonNull(arrival);
+
+        if (!(this.getCities().contains(origin) && this.getCities().contains(destination) )) {
+            throw new IllegalArgumentException("Provided cities must be part of the system");
+        }
+
+        if (!this.getAllTrains().contains(train)) {
+            throw new IllegalArgumentException("Provided train must be part of the system");
+        }
+
+        List<Trip> trainTrips = this.findOrderedTripsOfTrain(train);
 
         if (!trainTrips.isEmpty()) {
 
@@ -128,20 +142,24 @@ public class TicketReservationSystemImpl implements TicketReservationSystem {
     @Override
     public void delayTripArrival(Trip trip, Duration delay) {
         trip.addArrivalDelay(delay);
-        try {
             Optional<Trip> nextTrip = findNextTripOfTrain(trip.getTrain(), trip);
             if (nextTrip.isPresent()) {
                 delayTripDeparture(nextTrip.get(), delay);
             }
-        } catch (TripException e) {
-            e.printStackTrace();
-        }
     }
 
     @Override
-    public Optional<Trip> findNextTripOfTrain(Train train, Trip trip) throws TripException {
+    public Optional<Trip> findNextTripOfTrain(Train train, Trip trip) throws IllegalArgumentException, NullPointerException {
+        Objects.requireNonNull(train);
+        Objects.requireNonNull(trip);
+        if (!this.getAllTrains().contains(train)) {
+            throw new IllegalArgumentException("The provided train is not part of the system.");
+        }
+        if (!this.getAllTrips().contains(trip)) {
+            throw new IllegalArgumentException("The provided trip is not part of the system.");
+        }
         if (trip.getTrain() != train) {
-            throw new TripException();
+            throw new IllegalArgumentException("The provided trip is not linked with the provided train.");
         }
         List<Trip> orderedTrips = findOrderedTripsOfTrain(train);
         int nextTripIndex = orderedTrips.indexOf(trip) + 1;
@@ -150,9 +168,17 @@ public class TicketReservationSystemImpl implements TicketReservationSystem {
     }
 
     @Override
-    public Optional<Trip> findPreviousTripOfTrain(Train train, Trip trip) throws TripException {
+    public Optional<Trip> findPreviousTripOfTrain(Train train, Trip trip) throws IllegalArgumentException, NullPointerException {
+        Objects.requireNonNull(train);
+        Objects.requireNonNull(trip);
+        if (!this.getAllTrains().contains(train)) {
+            throw new IllegalArgumentException("The provided train is not part of the system.");
+        }
+        if (!this.getAllTrips().contains(trip)) {
+            throw new IllegalArgumentException("The provided trip is not part of the system.");
+        }
         if (trip.getTrain() != train) {
-            throw new TripException();
+            throw new IllegalArgumentException("The provided trip is not linked with the provided train.");
         }
         List<Trip> orderedTrips = findOrderedTripsOfTrain(train);
         int previousTripIndex = orderedTrips.indexOf(trip) - 1;