LocalDateTime总结

//------------------------------LocalDateTime总结-------------------------------------------------
    public static void main(String[] args) {

        //------------------------------【获取当前时间】---------------------------------------------------
        LocalDateTime nowTime = LocalDateTime.now();
        //结果：2021-02-20T09:45:44.527
        System.out.println(nowTime);
        //------------------------------【获取年月日】-----------------------------------------------------
        //【方法1】
        String a = nowTime.format(DateTimeFormatter.ISO_DATE);
        //结果：2021-02-20
        System.out.println(a);
        //【方法2】
        String b = nowTime.format(DateTimeFormatter.ofPattern("yyyy-MM-dd"));
        //结果：2021-02-20
        System.out.println(b);
        //------------------------------【获取时分秒】-----------------------------------------------------
        String c = nowTime.format(DateTimeFormatter.ofPattern("HH:mm:ss"));
        //结果：09:45:44
        System.out.println(c);
        //------------------------------【获取年月日时分秒毫秒】--------------------------------------------
        String d = nowTime.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss:SSS"));
        //结果：2021-02-20 09:45:44:527
        System.out.println(d);
        //------------------------------【获取秒数】-------------------------------------------------------
        Long second = LocalDateTime.now().toEpochSecond(ZoneOffset.of("+8"));
        //结果：1613785755
        System.out.println(second);
        //------------------------------【获取毫秒数】-----------------------------------------------------
        Long milliSecond = LocalDateTime.now().toInstant(ZoneOffset.of("+8")).toEpochMilli();
        //结果：1613785815633
        System.out.println(milliSecond);
        //------------------------------【毫秒转LocalDateTime】--------------------------------------------
        Long longTime = 1613786449976L;
        LocalDateTime ldt = Instant.ofEpochMilli(longTime).atZone(ZoneId.systemDefault()).toLocalDateTime();
        //结果：2021-02-20T10:00:49.976
        System.out.println(ldt);
        //------------------------------【String转LocalDateTime】------------------------------------------
        String dateTimeStr = "2021-02-20 09:50:15";
        DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        LocalDateTime dateTime = LocalDateTime.parse(dateTimeStr, df);
        //结果：2021-02-20T09:50:15
        System.out.println(dateTime);
        //------------------------------【LocalDateTime转String】------------------------------------------
        //除了下面的方法之外,上面类型转换的都可以看成是LocalDateTime转String  ZoneOffset.of("+8")意思为：默认时区为东8区
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        String dateTime2 = LocalDateTime.now(ZoneOffset.of("+8")).format(formatter);
        //结果：2021-02-20 09:55:52
        System.out.println(dateTime2);
        //------------------------------【LocalDateTime转Date】--------------------------------------------
        Date date = new Date();
        LocalDateTime localDateTime = date.toInstant().atOffset(ZoneOffset.of("+8")).toLocalDateTime();
        //结果：2021-02-20T09:59:14.719
        System.out.println(localDateTime);
        //------------------------------【Date转LocalDateTime】--------------------------------------------
        LocalDateTime localDateTime1 = LocalDateTime.now();
        Date date1 = Date.from(localDateTime1.toInstant(ZoneOffset.of("+8")));
        //结果：Sat Feb 20 10:00:49 CST 2021
        System.out.println(date1);
    }