code: public void add(String name, String value) {
          if (value == null)
              return;
  
          HttpField field = new HttpField(name, value);
          add(field);
      }
docs: Add to or set a field. If the field is allowed to have multiple values,
  add will add multiple headers of the same name.
  
  @param name  the name of the field
  @param value the value of the field.