public class Portal extends Tile
{
    public static final String START = "AA";
    public static final String EXIT = "ZZ";

    public Portal (Coordinate position, char portalId)
    {
        super(position, TileId.PORTAL);

        _horizontal = horizontalRepresentation;
    }

    private boolean _horizontal;
}

public class Portal extends Tile
{
    public static final String START = "AA";
    public static final String EXIT = "ZZ";

    public Portal (Coordinate position, char portalId)
    {
        super(position, TileId.PORTAL);
    }
}

Update Portal.java