import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

interface Freight {

  void accept(FreightVisitor visitor);
}

interface FreightVisitor {

  default void visit(Freight freight) {
  }

  default void visit(FixedFreight freight) {
    this.visit((Freight) freight);
  }

  default void visit(ByPriceFreight freight) {
    this.visit((Freight) freight);
  }

  default void visit(ByWeightFreight freight) {
    this.visit((Freight) freight);
  }
}

@Data
class FixedFreight implements Freight {

  int freight;

  @Override
  public void accept(FreightVisitor visitor) {
    visitor.visit(this);
  }
}

@Data
class ByPriceFreight implements Freight {

  int start = 0;
  int startLimit = 0;
  int priceUnit;
  int freightPerUnit;

  @Override
  public void accept(FreightVisitor visitor) {
    visitor.visit(this);
  }
}

@Data
@AllArgsConstructor
@NoArgsConstructor
class ByWeightFreight implements Freight {

  int start = 0;
  int startLimit = 0;
  int weightLimit;
  int freightPerUnit;

  @Override
  public void accept(FreightVisitor visitor) {
    visitor.visit(this);
  }
}


@Data
class ByWeightCalculateVisitor implements FreightVisitor {

  int weight;
  int freight = 0;

  ByWeightCalculateVisitor(int weight) {
    this.weight = weight;
  }

  @Override
  public void visit(ByWeightFreight freight) {
    this.freight = // do the calculation
  }
}


public class App {

  public static void main(String[] args) {
    ByWeightCalculateVisitor visitor = new ByWeightCalculateVisitor(10);
    ByWeightFreight byWeightFreight = new ByWeightFreight(0, 0, 10, 10);
    byWeightFreight.accept(visitor);

    System.out.println(visitor.getFreight());
  }
}