LiftState class

lift/src/lift/LiftMonitor.java

@@ -1,7 +1,5 @@
 package lift;
 
-import java.util.Arrays;
-
 enum Direction {
   UP,
   DOWN,
@@ -9,20 +7,12 @@ enum Direction {
 
 /** Lift monitor. Handles lift motion and various state. */
 public class LiftMonitor {
-  /** the floor the lift is currently on */
-  private int floor;
   /** Number of floors */
   private int nfloors;
-  /** true if the lift is moving, false if standing still with doors open */
-  private boolean moving;
-  /** Current direction of the lift */
-  private Direction direction;
   /** number of passengers waiting to enter the lift at the various floors */
   private PassengerQueue waitEntry;
   /** number of passengers (in lift) waiting to leave at the various floors */
   private PassengerQueue waitExit;
-  /** number of passengers currently in the lift */
-  private int load;
   /** view object passed from main */
   private LiftView view;
   /** State (open/closed) of door on current floor */
@@ -31,20 +21,19 @@ public class LiftMonitor {
   private int passengersEntering;
   /** Counter of number of passengers currently exiting the elevator */
   private int passengersExiting;
+  /** Lift state */
+  private LiftState liftState;
 
   /** Create new LiftMonitor */
   public LiftMonitor(LiftView v, int floors) {
-    floor = 0;
     nfloors = floors;
-    moving = true;
-    direction = Direction.UP;
     door = new Door();
     waitEntry = new PassengerQueue(nfloors);
     waitExit = new PassengerQueue(nfloors);
-    load = 0;
     view = v;
     passengersEntering = 0;
     passengersExiting = 0;
+    liftState = new LiftState(0, Direction.UP);
   }
 
   /** Increases the number of waiting passengers on given floor */
@@ -56,8 +45,8 @@ public class LiftMonitor {
   /** Handles passengers waiting to enter arriving lift */
   public synchronized void enterLift(int passengerFloor,
                                      int passengerDestination) {
-    while (floor != passengerFloor || load == 4 || moving ||
-        passengersEntering == 4) {
+    while (liftState.getFloor() != passengerFloor || liftState.getLoad() == 4 ||
+           liftState.isMoving() || passengersEntering == 4) {
       try {
         wait();
       } catch (InterruptedException e) {
@@ -65,9 +54,10 @@ public class LiftMonitor {
       }
     }
 
-    waitEntry.dec(floor);
+    waitEntry.dec(
+        liftState.getFloor()); // In practice, passengerFloor == floor here
     waitExit.inc(passengerDestination);
-    load++;
+    liftState.incLoad();
     passengersEntering++;
     notifyAll();
   }
@@ -80,7 +70,7 @@ public class LiftMonitor {
 
   /** Handles passengers waiting to exit lift */
   public synchronized void exitLift(int passengerDestination) {
-    while (floor != passengerDestination) {
+    while (liftState.getFloor() != passengerDestination) {
       try {
         wait();
       } catch (InterruptedException e) {
@@ -88,7 +78,7 @@ public class LiftMonitor {
       }
     }
     waitExit.dec(passengerDestination);
-    load--;
+    liftState.decLoad();
     passengersExiting++;
     notifyAll();
   }
@@ -114,13 +104,15 @@ public class LiftMonitor {
     }
 
     /** Stops the elevator to allow passengers to enter or exit */
-    while (waitEntry.get(floor) > 0 && load != 4 || waitExit.get(floor) > 0 ||
-        passengersEntering > 0 || passengersExiting > 0) {
+    while (waitEntry.get(liftState.getFloor()) > 0 &&
+               liftState.getLoad() != 4 ||
+           waitExit.get(liftState.getFloor()) > 0 || passengersEntering > 0 ||
+           passengersExiting > 0) {
       if (!door.isOpen()) {
-        view.openDoors(floor);
+        view.openDoors(liftState.getFloor());
         door.open();
       }
-      moving = false;
+      liftState.setMoving(false);
       notifyAll();
       try {
         wait();
@@ -129,13 +121,13 @@ public class LiftMonitor {
       }
     }
 
-    if (!moving)
+    if (!liftState.isMoving())
       view.closeDoors();
 
     if (door.isOpen())
       door.close();
 
-    moving = true;
+    liftState.setMoving(true);
 
     calculateDirection();
 
@@ -143,14 +135,16 @@ public class LiftMonitor {
      * Sends the elevators current position and next position to the LiftThread
      */
     int[] movingPositions = new int[2];
-    movingPositions[0] = floor;
-    movingPositions[1] = floor + (direction == Direction.UP ? 1 : -1);
+    movingPositions[0] = liftState.getFloor();
+    movingPositions[1] = liftState.getFloor() +
+                         (liftState.getDirection() == Direction.UP ? 1 : -1);
     return movingPositions;
   }
 
   /** Moves the elevator in the given direction */
   public synchronized void incrementFloor() {
-    floor = floor + (direction == Direction.UP ? 1 : -1);
+    liftState.setFloor(liftState.getFloor() +
+                       (liftState.getDirection() == Direction.UP ? 1 : -1));
   }
 
   /**
@@ -159,13 +153,19 @@ public class LiftMonitor {
    * to enter or exit on floors either above or below the elevator
    */
   private void calculateDirection() {
-    boolean noPassengersAbove = (waitEntry.totalAbove(floor) == 0 && waitExit.totalAbove(floor) == 0);
-    boolean noPassengersBelow = (waitEntry.totalBelow(floor) == 0 && waitExit.totalBelow(floor) == 0);
+    int floor = liftState.getFloor();
+    boolean noPassengersAbove =
+        (waitEntry.totalAbove(floor) == 0 && waitExit.totalAbove(floor) == 0);
+    boolean noPassengersBelow =
+        (waitEntry.totalBelow(floor) == 0 && waitExit.totalBelow(floor) == 0);
 
     if (floor == 0 || noPassengersBelow) {
-      direction = Direction.UP; // Always go up if at ground floor or no passengers below
+      liftState.setDirection(
+          Direction
+              .UP); // Always go up if at ground floor or no passengers below
     } else if (floor == nfloors - 1 || noPassengersAbove) {
-      direction = Direction.DOWN; // Always go down if at the top floor or no passengers above
+      liftState.setDirection(Direction.DOWN); // Always go down if at the top
+                                              // floor or no passengers above
     }
   }
 }

lift/src/lift/LiftState.java

@@ -0,0 +1,55 @@
+package lift;
+
+public class LiftState {
+    private int floor;
+    private Direction direction;
+    private boolean moving;
+    private int load;
+
+    public LiftState(int initialFloor, Direction initialDirection) {
+        this.floor = initialFloor;
+        this.direction = initialDirection;
+        this.moving = true;
+        this.load = 0;
+    }
+
+    public int getFloor() {
+        return floor;
+    }
+
+    public void setFloor(int floor) {
+        this.floor = floor;
+    }
+
+    public Direction getDirection() {
+        return direction;
+    }
+
+    public void setDirection(Direction direction) {
+        this.direction = direction;
+    }
+
+    public boolean isMoving() {
+        return moving;
+    }
+
+    public void setMoving(boolean moving) {
+        this.moving = moving;
+    }
+
+    public int getLoad() {
+        return load;
+    }
+
+    public void setLoad(int load) {
+        this.load = load;
+    }
+
+    public void incLoad() {
+        this.load++;
+    }
+
+    public void decLoad() {
+        this.load--;
+    }
+}