code: public static BitSet getBitSet(IAtomContainer atomContainer) {
          BitSet bitSet;
          int size = atomContainer.getBondCount();
  
          if (size != 0) {
              bitSet = new BitSet(size);
              for (int i = 0; i < size; i++) {
                  bitSet.set(i);
              }
          } else {
              bitSet = new BitSet();
          }
  
          return bitSet;
      }
docs: Transforms an AtomContainer into atom BitSet (which's size = number of bondA1
  in the atomContainer, all the bit are set to true).
  
  @param  atomContainer  AtomContainer to transform
  @return     The bitSet