code: public String getFieldDescription(int index)
      {
          ConstantInfo constantInfo = getConstantInfo(index);
          if (constantInfo instanceof Fieldref)
          {
              Fieldref fr = (Fieldref) getConstantInfo(index);
              int nt = fr.getName_and_type_index();
              NameAndType nat = (NameAndType) getConstantInfo(nt);
              int ni = nat.getName_index();
              int di = nat.getDescriptor_index();
              return getString(ni)+" "+getString(di);
          }
          return "unknown "+constantInfo;
      }
docs: Returns a descriptor to fields at index.
  @param index
  @return