// 2018-06-15
        LocalDate now = LocalDate.now();
        // 15:55:02.421
        LocalTime now2 = LocalTime.now();
        // 2018-06-15T15:56:12.619
        LocalDateTime now3 = LocalDateTime.now();
        
        // 把日期格式化指定的格式
        DateTimeFormatter dateTime = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss SSS");
        //2018-06-15 16:11:18 411
        String textNow = dateTime.format(now3);
        
        //把文本转化成日期
        String text = "2018-06-15 16:09:26 212";
        //2018-06-15T16:09:26.212
        LocalDateTime now4 = LocalDateTime.parse(text, dateTime);