java如何自定义List中的sort()排序,用于日期排序

//待排序的集合

List<String> list= new ArrayList<String>();

list.add( "2019-06" );

list.add( "2019-11" );

list.add( "2019-02" );

list.add( "2019-09" );

list.add( "2019-05" );

//自定义list排序，集合数据(月份)按升序排序;

final SimpleDateFormat sdft = new SimpleDateFormat( "yyyy-MM" );

Collections.sort(list, new Comparator<String>(){

     @Override

  public int compare(String month1, String month2) {

   int mark = 1 ;

   try {

       Date date1 = sdft.parse(month1);

       Date date2 = sdft.parse(month2);

       if (date1.getTime() < date2.getTime()){

        mark = - 1 ; //调整顺序,-1为不需要调整顺序;

       }

       if (month1.equals(month2)){

        mark =  0 ;

   }

   } catch (ParseException e) {

    LOG.error( "日期转换异常" , e);

    e.printStackTrace();

   }

  return mark;

  } //compare

});

Date() date1= new Date();

Date() date2= new SimpleDateFormat( "yyyy-MM-dd" ).parse( "2019-06-11" );

Boolean flag;

if (date1.before(date2)){

  flag= true ;

}

public   class   Test{

     public static void main(String[] args) {

         Student Student = new Student( "张1" , "6M" );

         Student Student1 = new Student( "张2" , "1M" );

         Student Student2 = new Student( "张4" , "5M" );

         Student Student3 = new Student( "张5" , "1M" );

         List<Student> list= new ArrayList<Student>();

         list.add(Student);

         list.add(Student1);

         list.add(Student2);

         list.add(Student3);

         Collections.sort(list, new Comparator<Student>() {

             @Override

             public int compare(Student o1, Student o2) {

                 return   o2.getAge()测试数据pareTo(o1.getAge());

             }

         });

         System.out.println(list.toString());

     }

}