Checkstyle and additional test

src/edu/kit/informatik/MainTest.java

@@ -134,6 +134,11 @@ class MainTest {
         cmpInOut("fuzz12_input.txt", "fuzz12_output.txt");
     }
 
+    @Test
+    void test13() throws IOException {
+        cmpInOut("test13_input.txt", "test13_output.txt");
+    }
+
     private void cmpInOut(String in, String out) throws IOException {
         System.setIn(new ByteArrayInputStream(readFile(in)));
         ByteArrayOutputStream output = new ByteArrayOutputStream();

src/edu/kit/informatik/model/RailwayNetwork.java

@@ -198,8 +198,8 @@ public class RailwayNetwork {
         } else if (touchingRails.length == 1) { // simply move along the rail
             return touchingRails[0].move(position, direction, 1);
         } // else: check movement along both rails and pick the correct rail
-        final Vector2D onRailOne = touchingRails[0].move(position, new Vector2D(direction), steps);
-        final Vector2D onRailTwo = touchingRails[1].move(position, new Vector2D(direction), steps);
+        final Vector2D onRailOne = touchingRails[0].move(position, direction, steps);
+        final Vector2D onRailTwo = touchingRails[1].move(position, direction, steps);
         // if we are stuck on the first rail
         //   or derail on the first rail
         //   or move in the correct direction on the second rail

src/edu/kit/informatik/model/Switch.java

@@ -153,6 +153,6 @@ public final class Switch extends Rail {
 
     @Override
     public int hashCode() {
-        return Objects.hash(positionOne, positionTwo, selection);
+        return Objects.hash(positionOne, positionTwo);
     }
 }

src/edu/kit/informatik/model/Track.java

@@ -78,9 +78,9 @@ public final class Track extends Rail {
         if (contains(nextPosition) || connectsTo(nextPosition)) {
             return nextPosition;
         } else if (direction.equals(getDirectionFrom(start))) {
-            return new Vector2D(end);
+            return end;
         } else if (direction.equals(getDirectionFrom(end))) {
-            return new Vector2D(start);
+            return start;
         } else if (position.equals(end) && !direction.equals(getDirectionFrom(start))) {
             return move(position, getDirectionFrom(end), steps);
         } else if (position.equals(start) && !direction.equals(getDirectionFrom(end))) {
@@ -119,7 +119,7 @@ public final class Track extends Rail {
      * @return start position of this track
      */
     public Vector2D getStart() {
-        return new Vector2D(start);
+        return start;
     }
 
     /**
@@ -128,7 +128,7 @@ public final class Track extends Rail {
      * @return end position of this track
      */
     public Vector2D getEnd() {
-        return new Vector2D(end);
+        return end;
     }
 
     @Override

src/edu/kit/informatik/model/Train.java

@@ -8,7 +8,6 @@ import java.util.LinkedList;
 import java.util.List;
 import java.util.Optional;
 import java.util.Set;
-import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
 /**
@@ -181,19 +180,17 @@ public final class Train implements Comparable<Train> {
     }
 
     /**
-     * @return position of the train head
+     * @return position of the front of the train
      */
     public Vector2D getFrontPosition() {
-        // make sure caller can not modify internal data
-        return positions != null ? new Vector2D(positions.getFirst()) : null;
+        return positions != null ? positions.getFirst() : null;
     }
 
     /**
-     * @return position of the rear of the train
+     * @return position of the back of the train
      */
     public Vector2D getRearPosition() {
-        // make sure caller can not modify internal data
-        return positions != null ? new Vector2D(positions.getLast()) : null;
+        return positions != null ? positions.getLast() : null;
     }
 
     /**
@@ -217,7 +214,8 @@ public final class Train implements Comparable<Train> {
      * @return a set of the rails this train occupies
      */
     public Set<Rail> getOccupiedRails() {
-        // make sure caller can not modify internal state
+        // need a copy (not a view) because the set will be modified when moving,
+        // but caller expects *current* state, not some updating state
         return new HashSet<>(occupiedRails);
     }
 
@@ -229,17 +227,14 @@ public final class Train implements Comparable<Train> {
      */
     public void moveTo(RailwayNetwork railNetwork, Vector2D nextPosition) {
         final Optional<Rail> railUnderBackOfTrain = railNetwork.findContainingRail(positions.getLast());
-        positions.getLast().subtractInPlace(getRearDirection());
-        if (positions.getLast().equals(positions.get(positions.size() - 2))) {
-            if (!railNetwork.findContainingRail(nextPosition).equals(railUnderBackOfTrain)
-                    || nextPosition == null) {
-                occupiedRails.remove(railUnderBackOfTrain.orElse(null));
-            }
+        positions.set(positions.size() - 1, positions.getLast().subtract(getRearDirection()));
+        if (positions.getLast().equals(positions.get(positions.size() - 2))) { // left a rail behind
+            occupiedRails.remove(railUnderBackOfTrain.orElse(null));
             positions.removeLast();
         }
         if (nextPosition != null) {
             // not derailing
-            positions.addFirst(new Vector2D(nextPosition));
+            positions.addFirst(nextPosition);
             simplifyPositions(railNetwork);
             occupiedRails.add(railNetwork.findRail(positions.get(1), nextPosition).get());
         } // else: derailing
@@ -255,24 +250,22 @@ public final class Train implements Comparable<Train> {
     public void moveBackTo(RailwayNetwork railNetwork, Vector2D backPosition) {
         // a common method for both directions would be a huge mess: requires at least six (!) extra parameters
         final Optional<Rail> railUnderFrontOfTrain = railNetwork.findContainingRail(positions.getFirst());
-        positions.getFirst().subtractInPlace(getDirection());
-        if (positions.getFirst().equals(positions.get(1))) {
-            if (!railNetwork.findContainingRail(backPosition).equals(railUnderFrontOfTrain)
-                    || backPosition == null) {
-                occupiedRails.remove(railUnderFrontOfTrain.orElse(null));
-            }
+        positions.set(0, positions.getFirst().subtract(getDirection()));
+        if (positions.getFirst().equals(positions.get(1))) { // left a rail behind
+            occupiedRails.remove(railUnderFrontOfTrain.orElse(null));
             positions.removeFirst();
         }
         if (backPosition != null) {
             // not derailing
-            positions.addLast(new Vector2D(backPosition));
+            positions.addLast(backPosition);
             simplifyPositions(railNetwork);
             occupiedRails.add(railNetwork.findRail(positions.get(positions.size() - 2), backPosition).get());
         } // else: derailing
     }
 
     /**
-     * Simplify internal position data. Removes positions that are contained between two other positions.
+     * Simplify internal position data.
+     * Removes positions that are contained between two other positions at the front or back of the train.
      *
      * @param railNetwork railway network to use
      */

src/edu/kit/informatik/model/Vector2D.java

@@ -4,19 +4,20 @@ import java.util.Objects;
 
 /**
  * A two-dimensional vector, usually a position or movement direction vector.
+ * An object of this class is immutable.
  *
  * @author Arne Keller
- * @version 1.0
+ * @version 1.1
  */
 public class Vector2D {
     /**
      * First coordinate of the vector, usually referred to as 'x'.
      */
-    private long x;
+    private final long x;
     /**
      * Second coordinate of the vector, usually referred to as 'y'.
      */
-    private long y;
+    private final long y;
 
     /**
      * Construct a new vector.
@@ -29,16 +30,6 @@ public class Vector2D {
         this.y = y;
     }
 
-    /**
-     * Copy a vector, creating a new object.
-     *
-     * @param other a vector
-     */
-    public Vector2D(Vector2D other) {
-        this.x = other.x;
-        this.y = other.y;
-    }
-
     /**
      * @param input two 32-bit numbers separated by a comma
      * @return a vector containing the two numbers, null otherwise
@@ -98,6 +89,40 @@ public class Vector2D {
                 || y == 0 && y == other.y && Long.signum(x) == Long.signum(other.x);
     }
 
+    /**
+     * @param movement vector to add
+     * @return component-wise sum of this vector and the other vector
+     */
+    public Vector2D add(Vector2D movement) {
+        return new Vector2D(x + movement.x, y + movement.y);
+    }
+
+    /**
+     * Subtract another vector from this one.
+     *
+     * @param other another vector
+     * @return the difference of this vector and the other vector
+     */
+    public Vector2D subtract(Vector2D other) {
+        return new Vector2D(x - other.x, y - other.y);
+    }
+
+    /**
+     * @return (- 1) * this vector
+     */
+    public Vector2D negated() {
+        return new Vector2D(-x, -y);
+    }
+
+    /**
+     * Calculate multiplier * this, and return a new vector.
+     *
+     * @param multiplier any scalar
+     * @return scaled vector
+     */
+    public Vector2D scale(long multiplier) {
+        return new Vector2D(x * multiplier, y * multiplier);
+    }
 
     /**
      * Normalize this vector. Will essentially return a new vector with (x/|x|, y/|y|).
@@ -116,51 +141,6 @@ public class Vector2D {
         }
     }
 
-    /**
-     * @return (- 1) * this vector
-     */
-    public Vector2D negated() {
-        return new Vector2D(-x, -y);
-    }
-
-    /**
-     * Subtract another vector from this one.
-     *
-     * @param other another vector
-     * @return the difference of this vector and the other vector
-     */
-    public Vector2D subtract(Vector2D other) {
-        return new Vector2D(x - other.x, y - other.y);
-    }
-
-    /**
-     * Subtract another vector from this one, modifying this vector.
-     *
-     * @param other another vector
-     */
-    public void subtractInPlace(Vector2D other) {
-        x -= other.x;
-        y -= other.y;
-    }
-
-    /**
-     * @param movement vector to add
-     * @return component-wise sum of this vector and the other vector
-     */
-    public Vector2D add(Vector2D movement) {
-        return new Vector2D(x + movement.x, y + movement.y);
-    }
-
-    /**
-     * Calculate multiplier * this, and return a new vector.
-     *
-     * @param multiplier any scalar
-     * @return scaled vector
-     */
-    public Vector2D scale(long multiplier) {
-        return new Vector2D(x * multiplier, y * multiplier);
-    }
-
     /**
      * @return the first component of this vector
      */

test13_input.txt

@@ -0,0 +1,11 @@
+add track (0,0) -> (10,0)
+add track (10,0) -> (20,0)
+add track (20,0) -> (30,0)
+create engine diesel T6 Lux 4 true true
+create engine diesel T6 Lumen 4 true false
+add train 1 T6-Lux
+add train 2 T6-Lumen
+put train 1 at (20,0) in direction 1,0
+put train 2 at (8,0) in direction 1,0
+step 3
+exit

test13_output.txt

@@ -0,0 +1,10 @@
+1
+2
+3
+T6-Lux
+T6-Lumen
+diesel engine T6-Lux added to train 1
+diesel engine T6-Lumen added to train 2
+OK
+OK
+Crash of train 1,2