LocalDateTime的一些用法

包括获取当前时间，指定特定时间。进行时间的加减等

LocalDateTime localDateTime3 = LocalDateTime.now();
LocalDate.now();
LocalTime.now();
localDateTime3.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
LocalDateTime localDateTime4 = localDateTime3.minus(23,ChronoUnit.MONTHS);
localDateTime4.atZone(ZoneId.systemDefault());
localDateTime4 = localDateTime4.withHour(3);
localDateTime4 = localDateTime4.withYear(2016);
localDateTime4 = localDateTime4.with(ChronoField.MONTH_OF_YEAR,3)

间隔计算

使用Duration进行 day,hour,minute,second等的计算 
使用Period进行Year,Month的计算

Duration duration = Duration.between(localDateTime,localDateTime4);
duration.toDays();
duration.toHours();
duration.toMinutes();
Period period2 = Period.between(localDateTime.toLocalDate(),localDateTime4.toLocalDate());
period2.getYears();
period2.getMonths();
period2.toTotalMonths();

与Date的转化，format为String

Date date = Date.from(localDateTime4.atZone(ZoneId.systemDefault()).toInstant());
LocalDateTime dateTime = LocalDateTime.ofInstant(date.toInstant(),ZoneId.systemDefault());

localDateTime3.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));

根据需求需要取得当天的零点

1.  
   LocalDateTime today_start = LocalDateTime.of(LocalDate.now(), LocalTime.MIN);//当天零点
2.  
   String td_st_str =today_start.format(DateTimeFormatter.ofPattern("yyyyMMddHHmmss"));

   获取当天结束时间

LocalDateTime today_end = LocalDateTime.of(LocalDate.now(), LocalTime.MAX);//当天零点

LocalDateTime与String日期互相转换

DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
LocalDateTime time = LocalDateTime.now();
String localTime = df.format(time);
LocalDateTime ldt = LocalDateTime.parse("2017-09-28 17:07:05",df);
System.out.println("LocalDateTime转成String类型的时间："+localTime);
System.out.println("String类型的时间转成LocalDateTime："+ldt);

控制台结果：

 LocalDateTime转成String类型的时间：2017-09-30 10:40:06
 String类型的时间转成LocalDateTime：2017-09-28T17:07:05

通过localdatetime获取long型毫秒时间

Long newSecond1 = LocalDateTime.now().toInstant(ZoneOffset.of("+8")).toEpochMilli();