code: public int getFlowAt( Direction direction ) {
          switch( direction ) {
          case E:
              return eFlow;
          case W:
              return wFlow;
          case N:
              return nFlow;
          case S:
              return sFlow;
          case EN:
              return enFlow;
          case NW:
              return nwFlow;
          case WS:
              return wsFlow;
          case SE:
              return seFlow;
          default:
              throw new IllegalArgumentException();
          }
      }
docs: Get the value of the flow in one of the surrounding direction.
  
  @param direction the {@link Direction}.
  @return the flow value.