Java日期格式化如何避免YYYY引发的时间异常
作者:myprince003
在编程中,日期格式化是一个常见的任务,使用不同的格式化选项可能会导致一些意外的结果,下面我们就来学习一下Java如何避免YYYY引发的时间异常吧
在编程中,日期格式化是一个常见的任务。使用不同的格式化选项可能会导致一些意外的结果。最近遇到一个问题,就是使用YYYY格式化选项会导致时间异常。
public static void main(String[] args) throws ParseException { SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); SimpleDateFormat sdf2 = new SimpleDateFormat("YYYY-MM-dd HH:mm:ss"); String time = "2023-12-31 23:59:59"; System.out.printf("yyyy-MM-dd HH:mm:ss: %s\n",sdf.format(sdf.parse(time))); System.out.printf("YYYY-MM-dd HH:mm:ss: %s\n",sdf2.format(sdf2.parse(time))); System.out.println("======================================"); String time2 = "2023-11-31 23:59:59"; //11月没有31号 System.out.printf("yyyy-MM-dd HH:mm:ss: %s\n",sdf.format(sdf.parse(time2))); System.out.printf("YYYY-MM-dd HH:mm:ss: %s\n",sdf2.format(sdf2.parse(time2))); System.out.println("======================================"); String time3 = "2023-10-31 23:59:59"; System.out.printf("yyyy-MM-dd HH:mm:ss: %s\n",sdf.format(sdf.parse(time3))); System.out.printf("YYYY-MM-dd HH:mm:ss: %s\n",sdf2.format(sdf2.parse(time3))); }
输出结果
yyyy-MM-dd HH:mm:ss: 2023-12-31 23:59:59
YYYY-MM-dd HH:mm:ss: 2023-01-01 23:59:59
======================================
yyyy-MM-dd HH:mm:ss: 2023-12-01 23:59:59
YYYY-MM-dd HH:mm:ss: 2023-01-01 23:59:59
======================================
yyyy-MM-dd HH:mm:ss: 2023-10-31 23:59:59
YYYY-MM-dd HH:mm:ss: 2023-01-01 23:59:59
网上查阅说大写的YYYY表示一个基于周的年份,它是根据周计算的年份,而不是基于日历的年份。通常情况下,两者的结果是相同的,但在跨年的第一周或最后一周可能会有差异。但这里发现无论怎么调整时间,YYYY-MM-dd HH:mm:ss格式化后一直是2023-01-01 23:59:59,不仅仅是在跨年的时候出现问题,具体原因尚不清楚
如何避免
定义通用的格式类,所有使用日期格式的地方都引用这个类,这个类中就定义好yyyy-MM-dd格式即可,这样就不会出现有人手误给大家埋雷了。
public class LocalDateUtils { /** * 显示年月日时分秒,例如 2023-10-31 09:51:53. */ public static final String DATETIME_PATTERN = "yyyy-MM-dd HH:mm:ss"; /** * 仅显示年月日,例如 2023-10-31. */ public static final String DATE_PATTERN = "yyyy-MM-dd"; private static final String YEAR = "year"; private static final String MONTH = "month"; private static final String WEEK = "week"; private static final String DAY = "day"; /** * 将日期转换为字符串,格式为:yyyy-MM-dd HH:mm:ss */ public static String getLocalDateTimeStr(LocalDateTime localDateTime) { return format(localDateTime, DATETIME_PATTERN); } /** * 将日期转换为字符串,格式为:yyyy-MM-dd */ public static String getLocalDateStr(LocalDateTime localDateTime) { return format(localDateTime, DATE_PATTERN); } /** * 将字符串转换为日期,格式为:yyyy-MM-dd HH:mm:ss */ public static LocalDateTime parseLocalDateTime(String localDateTimeStr) { DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern(DATETIME_PATTERN); return LocalDateTime.parse(localDateTimeStr, dateTimeFormatter); } /** * 将字符串转换为日期,格式为:yyyy-MM-dd */ public static LocalDate parseLocalDate(String localDateStr) { DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern(DATE_PATTERN); return LocalDate.parse(localDateStr, dateTimeFormatter); } /** * 将字符串转日期成Long类型的时间戳 */ public static Long convertLocalDateTimeToLong(String time) { LocalDateTime parse = parse(time, DATETIME_PATTERN); return LocalDateTime.from(parse).atZone(ZoneId.systemDefault()).toInstant().toEpochMilli(); } /** * 将字符串转日期成Long类型的时间戳 */ public static Long convertLocalDateToLong(String time) { LocalDateTime parse = parse(time, DATE_PATTERN); return LocalDateTime.from(parse).atZone(ZoneId.systemDefault()).toInstant().toEpochMilli(); } public static LocalDateTime parse(String time, String pattern) { DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern(pattern); return LocalDateTime.parse(time, dateTimeFormatter); } /** * 将Long类型的时间戳转换成String 类型的时间格式 */ public static String getLocalDateTimeStr(Long time) { return format(LocalDateTime.ofInstant(Instant.ofEpochMilli(time), ZoneId.systemDefault()), DATETIME_PATTERN); } /** * 将Long类型的时间戳转换成String 类型的时间格式,时间格式为:yyyy-MM-dd */ public static String getLocalDateStr(Long time) { return format(LocalDateTime.ofInstant(Instant.ofEpochMilli(time), ZoneId.systemDefault()), DATE_PATTERN); } /** * 获取日期时间字符串 */ public static String format(TemporalAccessor temporal, String pattern) { DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern(pattern); return dateTimeFormatter.format(temporal); } /** * 取本月第一天 */ public static LocalDate firstDayOfThisMonth() { LocalDate today = LocalDate.now(); return today.with(TemporalAdjusters.firstDayOfMonth()); } /** * 取本月第N天 */ public static LocalDate dayOfThisMonth(int n) { LocalDate today = LocalDate.now(); return today.withDayOfMonth(n); } /** * 取本月最后一天 */ public static LocalDate lastDayOfThisMonth() { LocalDate today = LocalDate.now(); return today.with(TemporalAdjusters.lastDayOfMonth()); } /** * 获取指定日期时间加上指定数量日期时间单位之后的日期时间. */ public static LocalDateTime plus(LocalDateTime localDateTime, int num, ChronoUnit chronoUnit) { return localDateTime.plus(num, chronoUnit); } /** * 获取指定日期时间减去指定数量日期时间单位之后的日期时间. */ public static LocalDateTime minus(LocalDateTime localDateTime, int num, ChronoUnit chronoUnit) { return localDateTime.minus(num, chronoUnit); } /** * 根据ChronoUnit计算两个日期时间之间相隔日期时间 */ public static long getChronoUnitBetween(LocalDateTime start, LocalDateTime end, ChronoUnit chronoUnit) { return Math.abs(start.until(end, chronoUnit)); } /** * 根据ChronoUnit计算两个日期之间相隔年数或月数或天数 */ public static long getChronoUnitBetween(LocalDate start, LocalDate end, ChronoUnit chronoUnit) { return Math.abs(start.until(end, chronoUnit)); } /** * 切割日期。按照周期切割成小段日期段。例如: <br> * * @param startDate 开始日期(yyyy-MM-dd) * @param endDate 结束日期(yyyy-MM-dd) * @param period 周期(天,周,月,年) * @return 切割之后的日期集合 * <li>startDate="2023-10-27",endDate="2023-10-31",period="day"</li> * <li>结果为:[2023-10-27, 2023-10-28, 2023-10-29, 2023-10-03,2023-10-31]</li><br> * <li>startDate="2023-10-27",endDate="2023-10-31",period="week"</li> * <li>结果为:[2023-10-27,2023-10-31]</li><br> * <li>startDate="2023-10-27",endDate="2023-10-31",period="month"</li> * <li>结果为:[2023-10-27,2023-10-31]</li><br> * <li>startDate="2023-10-27",endDate="2023-10-31",period="year"</li> * <li>结果为:[2023-10-27,2023-10-31]</li><br> */ public static List<String> listDateStrs(String startDate, String endDate, String period) { List<String> result = new ArrayList<>(); DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern(DATE_PATTERN); LocalDate end = LocalDate.parse(endDate, dateTimeFormatter); LocalDate start = LocalDate.parse(startDate, dateTimeFormatter); LocalDate tmp = start; switch (period) { case DAY: while (start.isBefore(end) || start.isEqual(end)) { result.add(start.toString()); start = start.plusDays(1); } break; case WEEK: while (tmp.isBefore(end) || tmp.isEqual(end)) { if (tmp.plusDays(6).isAfter(end)) { result.add(tmp.toString() + "," + end); } else { result.add(tmp.toString() + "," + tmp.plusDays(6)); } tmp = tmp.plusDays(7); } break; case MONTH: while (tmp.isBefore(end) || tmp.isEqual(end)) { LocalDate lastDayOfMonth = tmp.with(TemporalAdjusters.lastDayOfMonth()); if (lastDayOfMonth.isAfter(end)) { result.add(tmp.toString() + "," + end); } else { result.add(tmp.toString() + "," + lastDayOfMonth); } tmp = lastDayOfMonth.plusDays(1); } break; case YEAR: while (tmp.isBefore(end) || tmp.isEqual(end)) { LocalDate lastDayOfYear = tmp.with(TemporalAdjusters.lastDayOfYear()); if (lastDayOfYear.isAfter(end)) { result.add(tmp.toString() + "," + end); } else { result.add(tmp.toString() + "," + lastDayOfYear); } tmp = lastDayOfYear.plusDays(1); } break; default: break; } return result; } }
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