code: public static int getMolecularGraphRadius(IAtomContainer atomContainer) {
          int natom = atomContainer.getAtomCount();
  
          int[][] admat = AdjacencyMatrix.getMatrix(atomContainer);
          int[][] distanceMatrix = computeFloydAPSP(admat);
  
          int[] eta = new int[natom];
          for (int i = 0; i < natom; i++) {
              int max = -99999;
              for (int j = 0; j < natom; j++) {
                  if (distanceMatrix[i][j] > max) max = distanceMatrix[i][j];
              }
              eta[i] = max;
          }
          int min = 999999;
          for (int anEta : eta) {
              if (anEta < min) min = anEta;
          }
          return min;
      }
docs: Returns the radius of the molecular graph.
  
  @param atomContainer The molecule to consider
  @return The topological radius