LocalDateTime 和LocalDate。

获取当前日期：LocalDate   now = LocalDate.now();

int year = localDate.getYear();

int month = localDate.getMonthValue();

int day = localDate.getDayOfMonth();

获取前一天：now.minusDays(1); 

获取前一周：now.minusWeeks(1);

获取前一月：now.minusMonths(1);

获取前一年：now.minusYears(1);

获取后一天：now.plusDays(1);

获取后一周：now.plusWeeks(1);

获取后一月：now.plusMonths(1);

获取后一年：now.plusYears(1);

获取当前时间：LocalDateTime nowTime = LocalDate.now();

获取前一小时：nowTime.minusHours(1);

获取前一分钟：nowTime.minusMinutes(1);

获取前30秒：nowTime.minusSeconds(30);

获取后一小时：now.plusHours(1);

获取后一分钟：now.plusMinutes(1);

获取后30秒：now.plusSeconds(30);

nowTime也可以获取前一天，前一月。。。后一天，后一月。。。

时间格式转换：

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

String nowTimeString = nowTime.format(format);

LocalDateTime nowTimechange = LocalDateTime.parse(nowTimeString,format);

时间比较大小

LocalDateTime time1 = LocalDateTime.of(2018, 5, 23, 8, 20,30); or time1 = LocalDateTime.parse("2018-05-12 08:30:30",format);

LocalDateTime time2 = LocalDateTime.of(2018, 4, 10, 18, 30, 20);  or  time2 = LocalDateTime.parse("2018-04-20 16:30:30",format);

time1.isAfter(time2)       true

time1.isEqual(time2)      false

time1.isBefore(time2)    false

//获取指定的日期

LocalDate specifiedDay = LocalDate.of(2008, 8, 18);