code: public static boolean sourcesNet( RandomIter flowIterator, int[] colRow, int num, RandomIter netNum ) {
          int[][] dir = {{0, 0, 0}, {1, 0, 5}, {1, -1, 6}, {0, -1, 7}, {-1, -1, 8}, {-1, 0, 1}, {-1, 1, 2}, {0, 1, 3}, {1, 1, 4}};
  
          if (flowIterator.getSampleDouble(colRow[0], colRow[1], 0) <= 10.0
                  && flowIterator.getSampleDouble(colRow[0], colRow[1], 0) > 0.0) {
              for( int k = 1; k <= 8; k++ ) {
                  if (flowIterator.getSampleDouble(colRow[0] + dir[k][0], colRow[1] + dir[k][1], 0) == dir[k][2]
                          && netNum.getSampleDouble(colRow[0] + dir[k][0], colRow[1] + dir[k][1], 0) == num) {
                      return false;
                  }
              }
              return true;
          } else {
              return false;
          }
  
      }
docs: Controls if the considered point is a source in the network map.
  
  @param flowIterator
  {@link RandomIter iterator} of flowdirections map
  @param colRow the col and row of the point to check.
  @param num
  channel number
  @param netNum
  {@link RandomIter iterator} of the netnumbering map.
  @return