code: public Direction isSameValueNeighborOf( GridNode otherNode ) {
          Direction direction = isNeighborOf(otherNode);
          if (direction != null && NumericsUtilities.dEq(elevation, otherNode.elevation)) {
              return direction;
          }
          return null;
      }
docs: Checks if the supplied node is adjacent to the current and has the same value.
  
  @return the {@link Direction} if the two cells touch and have the same value, else <code>null</code>.