how do I convert object properties of type String to int sorting?
attribute area_size is a String type attribute, but the values are all numeric types. I want to sort it first by Id, and then by the size of area_size. Here"s my code:

defectFS.stream()
            .sorted(Comparator.comparing(WppDefectF::getId)
                .thenComparing((d1,d2) -> 
                  Integer.compare(Integer.parseInt(d1.getArea_size()), Integer.parseInt(d1.getArea_size()))
                );

when I use the above code to implement it, I find that the values of D1 and D2 are always the same, so the order is out of order. How to sort the String attributes of lambda expressions in java8?