code: public Direction isNeighborOf( GridNode otherNode ) {
          Direction[] orderedDirs = Direction.getOrderedDirs();
          for( int i = 0; i < orderedDirs.length; i++ ) {
              Direction direction = orderedDirs[i];
              int newCol = col + direction.col;
              int newRow = row + direction.row;
              if (otherNode.col == newCol && otherNode.row == newRow) {
                  return direction;
              }
          }
          return null;
      }
docs: Checks if the supplied node is adjacent to the current.
  
  @return the {@link Direction} if the two cells touch, else <code>null</code>.