code: public void add(Attribute attr) {
          int symbol;
          List<Attribute> lst;
  
          if (locate(attr) == -1) {
              symbol = attr.symbol;
              while (attrs.size() <= symbol) {
                  attrs.add(new ArrayList<Attribute>());
              }
              lst = attrs.get(symbol);
              lst.add(attr);
          }
      }
docs: adds if new ...