关于LocalDateTime最常用方法和时间转换方式

public static LocalDateTime parseStringToDateTime(String time, String format) {
　　DateTimeFormatter df = DateTimeFormatter.ofPattern(format);
　　return LocalDateTime.parse(time, df);
}

public static String getDateTimeToString(LocalDateTime localDateTime, String format) {
　　DateTimeFormatter formatter = DateTimeFormatter.ofPattern(format);
　　return localDateTime.format(formatter);
}

String utc = getUTCMillisecondFromTimestamp(1539718265123);
System.out.println(utc);

输出：2018-10-16T19:31:05.123Z

String utc = getUTCMillisecondFromTimestamp(1539718265000);
System.out.println(utc);

输出：2018-10-16T19:31:05Z

/**
	 * 将UTC时间戳转为UTC字符串（精确到秒）
	 *
	 * @param timestamp
	 * @return
	 */
	public static String getUTCStrFromTimestamp(long timestamp) {
		DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss'Z'");
		// 北京时间：ZoneId.of("UTC+8")；系统默认时间：ZoneId.systemDefault() 
		LocalDateTime localDateTime = LocalDateTime.ofInstant(Instant.ofEpochMilli(timestamp), ZoneId.of("UTC"));
		String utc = localDateTime.format(formatter);
		return utc;
	}

String utc = getUTCStrFromTimestamp(1539718265123);
System.out.println(utc);

输出：2018-10-16T19:31:05Z

	/**
	 * 将时间戳转为UTC字符串(若毫秒为000则不显示毫秒，若毫秒位不为000则显示毫秒)
	 * 
	 * 返回格式：2018-10-16T19:31:05.123Z
	 * 
	 * @param timestamp
	 * @return
	 */
	public static String getUTCMillisecondFromTimestamp(long timestamp) {
		Instant instant = Instant.ofEpochMilli(timestamp);
		String utcString = instant.toString();
		return utcString;
	}

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss'Z'");

String startTime = LocalDateTime.now().withHour(0).withMinute(0).withSecond(0).withNano(0).format(formatter);

String endTime = LocalDateTime.now().withHour(23).withMinute(59).withSecond(59).withNano(999_999_999).format(formatter);

/**
	 * 返回目标月份的最后一天
	 *
	 * @param sourceDate  目标月份
	 * @param monthOffset 月份偏移量
	 * @return
	 */
	private LocalDate getLastDateOfMonth(LocalDate sourceDate, int monthOffset) {
		return sourceDate.plusMonths(monthOffset).with(TemporalAdjusters.lastDayOfMonth());
	}

LocalDate date = LocalDate.of(2021, 4, 20);
LocalDateTime startTime = LocalDateTime.of(date, LocalTime.MIN);
LocalDateTime endTime = LocalDateTime.of(date, LocalTime.MAX);

/**
	 * 获得一个(毫秒)时间戳的十分钟起始时间戳
	 * 
	 * 如：输入1534930875000(2018-08-22 17:41:15)的时间戳返回1534930800000(2018-08-22 17:40:00)的时间戳
	 * 
	 * @param timestrap
	 * 
	 * 
	 * @return
	 */
	public static long getTenMinuteStartTimestrap(long timestamp) {
		LocalDateTime localDateTime = getLocalDateTimeByTimestamp(timestamp);
		int minute = localDateTime.getMinute();
		// 分钟个位数置为0
		int minute_floor = minute / 10 * 10;
		LocalDateTime startLocalDateTime = localDateTime.withMinute(minute_floor).withSecond(0).withNano(0);
		long startTimestamp = getTimestampByLocalDateTime(startLocalDateTime);
		return startTimestamp;
	}

	/**
	 * Long毫秒时间戳转LocalDateTime
	 */
	public static LocalDateTime getLocalDateTimeByTimestamp(long timestamp) {
		Instant instant = Instant.ofEpochMilli(timestamp);
		LocalDateTime localDateTime = LocalDateTime.ofInstant(instant, ZoneOffset.UTC);
		return localDateTime;
	}

	/**
	 * 根据毫秒时间戳获取LocalDateTime
	 * @param localDateTime
	 * @return
	 */
	public static long getTimestampByLocalDateTime(LocalDateTime localDateTime) {
		long timestamp = localDateTime.atZone(ZoneId.of("UTC")).toInstant().toEpochMilli();
		return timestamp;
	}

/**
	 * 时间戳根据时区转为当地日期
	 * @param timestamp
	 * @param timezone
	 * @return
	 */
	public static Date getLocalDateByTimezone(long timestamp, int timezone) {
		Instant instant = Instant.ofEpochMilli(timestamp);
		LocalDateTime localDateTime = LocalDateTime.ofInstant(instant, ZoneOffset.UTC);
		// 当地时间
		LocalDateTime localDate = localDateTime.plusHours(timezone);
		DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss'Z'");
		String localDateTimeStr = df.format(localDate);
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'");
		Date date = null;
		try {
			date = sdf.parse(localDateTimeStr);
		} catch (ParseException e) {
			e.printStackTrace();
		}
		return date;
	}

Date date = Date.from(LocalDateTime.now().atZone(ZoneId.systemDefault()).toInstant());

Date todayDate = new Date();
LocalDateTime ldt = todayDate.toInstant()
        .atZone( ZoneId.systemDefault() )
        .toLocalDateTime();

long second = Instant.ofEpochMilli(1636338645000L).getEpochSecond();

long second = Instant.ofEpochSecond(1636338645L).toEpochMilli();