java中开始日期和结束日期的排序列表

Question

我有开始日期和结束日期。如何排序。 这是我的尝试，但它只适用于一个日期列表

String sorted_date = "";
  String from_date="";
  List<String> listDates = new ArrayList<String>();
  for (int i = 0; i < leaveTransactionDetail.size(); i++) {
  if (leaveTransactionDetail.get(i).get("from_date").toString().trim().equals("0000-00-00")) {
      sorted_date = leaveTransactionDetail.get(i).get("to_date").toString().trim();

        } else {
          sorted_date = leaveTransactionDetail.get(i).get("from_date").toString().trim();
       
          }
          listDates.add(sorted_date);
    }
          Collections.sort(listDates);

          out.println("After sorting: " + listDates);

这是我的桌子

我希望输出日期按排序顺序

Answer 1

对我来说，你必须使用一个新对象。

public class DateStartEnd implements Comparable {
        public String start, end;

        public DateStartEnd(String start, String end) {
            this.start = start;
            this.end = end;
        }
        
        public String getStart() {
            return start;
        }
        
        public String getEnd() {
            return end;
        }
        
        @Override
        public String toString() {
            return "Start:" + start + ",End:" + end; // here it's just to check result, such as I test with different year, it's "showable" for me
        }

        @Override
        public int compareTo(Object o) { // method from comparable interface
            if(!(o instanceof DateStartEnd))
                return 0; // if it's not good object type
            DateStartEnd other = (DateStartEnd) o; // cast to current one
            return getStart().compareTo(other.getEnd()); // compare date between current and next
        }
}

然后现在我们创建自己的对象并比较它们：

List<DateStartEnd> dates = new ArrayList<>();
for (int i = 0; i < leaveTransactionDetail.size(); i++) {
   // get from and to dates
   String fromDate = leaveTransactionDetail.get(i).get("from_date").toString().trim();
   String toDate = leaveTransactionDetail.get(i).get("to_date").toString().trim();
   dates.add(new DateStartEnd(fromDate, toDate)); // add to all dates
}

Collections.sort(dates); // this will use the compare method, define in the object thanks to "Comparable" interface

System.out.println("After sorting: " + dates); // print result