java8利用LocalDateTime类操作时间

//获取LocalDateTime格式当前时间 2020-07-15T17:01:07.371public static String nowTime(String type) {switch (type) {case "":retu LocalDateTime.now().toString();case "年月日":retu LocalDate.now().toString();case "时分秒":retu LocalTime.now().toString();default:System.out.println("参数错误：" + type);}retu null;}//将long类型的时间戳转为LocalDateTime格式时间public static LocalDateTime getDateTimeOfTimestamp(long timestamp) {Instant instant = Instant.ofEpochMilli(timestamp);ZoneId zone = ZoneId.systemDefault();retu LocalDateTime.ofInstant(instant, zone);}//将LocalDateTime转为long类型的时间戳public static long getTimestampOfDateTime(LocalDateTime localDateTime) {ZoneId zone = ZoneId.systemDefault();Instant instant = localDateTime.atZone(zone).toInstant();retu instant.toEpochMilli();}//获取当前时间加指定时间,年、月、周、日、时、分、秒public static String time_plusTime(long Years, long Months, long Weeks, long Days, long Hours, long Minutes, long Seconds) {LocalDateTime dt = LocalDateTime.now(); // 当前日期和时间LocalDateTime dt2 = dt.plusYears(Years).plusMonths(Months).plusWeeks(Weeks).plusDays(Days).plusHours(Hours).plusMinutes(Minutes).plusSeconds(Seconds);retu String.valueOf(dt2);}//获取当前时间减指定时间,年、月、周、日、时、分、秒public static String time_minusTime(long Years, long Months, long Weeks, long Days, long Hours, long Minutes, long Seconds) {LocalDateTime dt = LocalDateTime.now(); // 当前日期和时间LocalDateTime dt2 = dt.minusYears(Years).minusMonths(Months).minusWeeks(Weeks).minusDays(Days).minusHours(Hours).minusMinutes(Minutes).minusSeconds(Seconds);retu String.valueOf(dt2);}//判断当前时间是属于上午还是下午public static String moing_or_afteoon() {LocalDateTime now = LocalDateTime.now();switch (now.get(ChronoField.AMPM_OF_DAY)) {case 0:retu "上午";case 1:retu "下午";}retu "";}////返回当前时间的其中一项：如年、月、日、时public static int nowTime_onlyOne(String timeUnit) {switch (timeUnit) {case "年":retu LocalDateTime.now().getYear();case "月":retu LocalDateTime.now().getMonthValue();case "日":retu LocalDateTime.now().getDayOfMonth();case "时":retu LocalDateTime.now().getHour();//24小时制case "分":retu LocalDateTime.now().getMinute();case "秒":retu LocalDateTime.now().getSecond();case "毫秒":retu LocalDateTime.now().getNano() / 1000_000;//毫秒，只返回前3位}retu 0;}