java时间

    SimpleDateFormat ft = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    String time = "2021-6-9 11:30:30";
    String time2 = "2021-6-9 11:30:31";
    Date date = ft.parse(time);
    Date date2 = ft.parse(time2);
    System.out.println(date.getTime() > date2.getTime());

//        字符串转日期
        String t1 = "2022/9/13 14:28:43";
        String t2 = "2022/9/13 14:28:42";
        SimpleDateFormat df = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
        Date parse = df.parse(t1);
        Date parse2 = df.parse(t2);
        System.out.println(parse);


//        日历
        Calendar instance = Calendar.getInstance();
        instance.setTime(parse);
//        增加一年
        instance.add(Calendar.YEAR,1);
        System.out.println(df.format(instance.getTime()));


//        LocalDateTime
        String t3 = "2022/09/13 14:29:42";
        String t4 = "2022/09/13 14:28:42";
        DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy/MM/dd HH:mm:ss");
        LocalDateTime lt = LocalDateTime.parse(t3,dateTimeFormatter);
        LocalDateTime lt2 = LocalDateTime.parse(t4,dateTimeFormatter);
        System.out.println("加2天: " + dateTimeFormatter.format(lt.plus(2, ChronoUnit.DAYS)));


        //当前时间基础上，指定本年当中的第几天，取值范围为1-365,366
        LocalDateTime withDayOfYearResult = lt.withDayOfYear(200);
//当前时间基础上，指定本月当中的第几天，取值范围为1-29,30,31
        LocalDateTime withDayOfMonthResult = lt.withDayOfMonth(5);
//当前时间基础上，直接指定年份
        LocalDateTime withYearResult = lt.withYear(2017);
//当前时间基础上，直接指定月份
        LocalDateTime withMonthResult = lt.withMonth(5);

        //Duration:用于计算两个“时间”间隔
        Duration between = Duration.between(lt, lt2);
        System.out.println("分：" + -between.toMinutes());
        System.out.println("毫秒：" + -between.toMillis());

//        Period:用于计算两个“日期”间隔
        Period between1 = Period.between(LocalDate.from(lt), LocalDate.from(lt2));
        System.out.println("年: " + between1.getYears());