Collections.sort list内部排序

public class ComparatorUser implements Comparator{
   public int compare(Object arg0, Object arg1) {
    ReqInfoFurikaeDto req0=(ReqInfoFurikaeDto)arg0;
    ReqInfoFurikaeDto req1=(ReqInfoFurikaeDto)arg1;
    return req0.getKanrenReceiptSeikyuNengetsu().compareTo(req1.getKanrenReceiptSeikyuNengetsu());
   }
 }

ComparatorUser comparator=new ComparatorUser();
      Collections.sort(reqInfoFurikaeDtoList, comparator);
    return reqInfoFurikaeDtoList.get(0);