code: private Group getNewGroup(String recordName,Character aminoCode1, String aminoCode3) {
  
  		Group g =  ChemCompGroupFactory.getGroupFromChemCompDictionary(aminoCode3);
  		if ( g != null && !g.getChemComp().isEmpty())
  			return g;
  
  
  		Group group;
  		if (aminoCode1 == null || StructureTools.UNKNOWN_GROUP_LABEL == aminoCode1 ){
  			group = new HetatomImpl();
  
  		} else if(StructureTools.isNucleotide(aminoCode3))  {
  			// it is a nucleotide
  			NucleotideImpl nu = new NucleotideImpl();
  			group = nu;
  
  		} else {
  			AminoAcidImpl aa = new AminoAcidImpl() ;
  			aa.setAminoType(aminoCode1);
  			group = aa ;
  		}
  
  		//		System.out.println("new resNum type: "+ resNum.getType() );
  		return  group ;
  	}
docs: initiate new resNum, either Hetatom, Nucleotide, or AminoAcid