日期字段解析错误 [英] Parsing error for date field

问题描述

我想将 YYYY-MM-DD 格式的日期解析为 YYYYMMDD .如果使用以下功能，它将返回 YYYYMMDD 格式，但具有不同的DD.即: 2013-05-16 变为 20130515

I want to parse a date in YYYY-MM-DD format to YYYYMMDD. If I use the following function, it returns me a YYYYMMDD format but with a different DD. i.E: 2013-05-16 BECOMES 20130515

道歉的道歉:)我是Java的新手.

Apologies for sounding illiterate :) I am new to Java.

任何帮助将不胜感激.

String TestDate=yyyymmddParser.format(oLifEExtension.TestDate().getTime());
                    sb.append(TestDate)

推荐答案

不确定问题是针对 java.util.Date (日期加时间)还是 java.sql.Date (仅日期).在这两种情况下，都应该使用现代的java.time类，而不要使用麻烦的旧式日期时间类.

Not sure if the Question was meant for java.util.Date (a date plus time-of-day) or a java.sql.Date (a date-only). In both cases, you should be using the modern java.time classes rather than the troublesome legacy date-time classes.

其他一些 java.sql.Date 问题被链接为该问题的重复项.所以我在这里处理两个类(sql& util).

Some other java.sql.Date questions are linked as duplicates of this one. So I handle both classes (sql & util) here.

旧版 java.util.Date 类表示UTC时间轴上的时刻.这意味着一个带有日期的日期.诀窍是您的输入字符串仅用于日期值.您可以首先将字符串解析为仅日期的值，然后根据需要分配时间.

The legacy java.util.Date class represents a moment on the timeline in UTC. This means a date with a time-of-day. The trick is that your input string is for a date-only value. You can first parse your string as a date-only value, then assign a time-of-day if desired.

您的输入字符串符合YYYY-MM-DD的标准 ISO 8601 格式.解析/生成字符串时，java.time类默认为标准格式.因此，无需指定格式设置模式.

Your input string complies with the standard ISO 8601 format of YYYY-MM-DD. The java.time classes default to the standard formats when parsing/generating strings. So no need to specify a formatting pattern.

LocalDate ld = LocalDate.parse( "2013-05-16" ) ;

在一天中的某个时间，您可能需要一天的第一时刻.不要以为第一时间是 00:00:00 .在某些时区，诸如夏令时(DST)之类的异常可能会导致一天在不同的时间开始，例如 01:00:00 .为了解决这种异常情况，我们必须在确定一天的第一时刻时指定一个时区.

For a time-of-day, you probably want the first moment of the day. Do not assume the first moment is 00:00:00. In some time zones an anomaly such as Daylight Saving Time (DST) may cause a day to start at a different time such as 01:00:00. To account for such anomalies, we must specify a time zone in determining the first moment of the day.

以大陆/地区，例如 美国/蒙特利尔 ， 非洲/卡萨布兰卡 或 Pacific/Auckland .切勿使用3-4个字母的缩写，例如 EST 或 IST ，因为它们不是真正的时区，不是标准化的，甚至不是唯一的(！).

Specify a proper time zone name in the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).

ZoneId z = ZoneId.of( "America/Montreal" ) ;

在询问java.time以确定该天的第一时刻时应用该区域.我们产生一个 ZonedDateTime 对象作为结果.

Apply that zone in asking java.time to determine the first moment of the day. We produce a ZonedDateTime object as the result.

ZonedDateTime zdt = ld.atStartOfDay( z ) ;

如果您需要一天中的特定时间，请应用 LocalTime 对象.请记住，您的时间在该特定区域的特定日期可能无效.例如，您可能要指定DST转换期间发生的时间.在这种情况下， ZonedDateTime 类具有用于调整以适应的策略.请务必阅读文档，以了解该策略以及由此产生的行为.

If you desire a specific time of day, apply a LocalTime object. Keep in mind that your time-of-day may not be valid on that particular date for that particular zone. For example, you may be specifying a time-of-day occurring during a DST cutover. In such a case, the ZonedDateTime class has a policy for adjusting to accommodate. Be sure to read the documentation to understand that policy and the resulting behavior.

LocalTime lt = LocalTime.of( 12 , 0 ) ; 
ZonedDateTime zdt = ZonedDateTime.of( ld , lt , z ) ;  // Time-of-day may be adjusted as needed.

java.sql.Date

无需使用 java.sql.Date .该类由 LocalDate 替换. LocalDate class表示不带日期和时区的仅日期值.

java.sql.Date

No need to use java.sql.Date. That class is replaced by LocalDate. The LocalDate class represents a date-only value without time-of-day and without time zone.

符合JDBC 4.2的JDBC驱动程序可以通过调用以下方法直接处理java.time类型:

JDBC drivers that comply with JDBC 4.2 can deal directly with java.time types by calling:

• 要向用户展示 LocalDate ，请生成一个字符串，以显示在用户界面中.使用 DateTimeFormatter 自动进行本地化.要本地化，请指定:

  For presentation of the LocalDate to the user, generate a String for display in your user-interface. Use a DateTimeFormatter to automatically localize. To localize, specify:

  • FormatStyle 确定字符串应为多长或缩写.
  • Locale 确定(a)日名，月名等的翻译所用的人类语言，以及(b)决定缩写，大写，标点，分隔符等问题的文化规范.

  示例:

  Locale l = Locale.CANADA_FRENCH ; 
  DateTimeFormatter f = DateTimeFormatter.ofLocalizedDate( FormatStyle.MEDIUM ).withLocale( l );
  String output = zdt.format( f );
  

  您也可以朝另一个方向发展，

  You can go the other direction as well, parsing an input string to get a date.

  LocalDate ld = LocalDate.parse( input , f ) ;
  

  捕获用户输入错误或意外时引发的异常.

  Trap for the exception thrown if the user’s input is faulty or unexpected.

  try{ 
      LocalDate ld = LocalDate.parse( input , f ) ;
      myPrepStmt.setObject( … , ld ) ;
  } catch ( DateTimeParseException e ) {
      … // Handle the error condition of faulty/unexpected input by user.
  }
  

  ---

  关于java.time

  java.time 框架已内置在Java 8及更高版本中.这些类取代了麻烦的旧版日期时间类，例如 Calendar ，& SimpleDateFormat

  ---

  About java.time

  The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

  Joda-Time 项目，现在位于

  The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

  要了解更多信息，请参见 Oracle教程.并在Stack Overflow中搜索许多示例和说明.规范为 JSR 310 .

  To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

  在哪里获取java.time类?

  Where to obtain the java.time classes?

  • Java SE 8 ， Java SE 9 和更高版本
    • 内置.
    • 具有捆绑的实现的标准Java API的一部分.
    • Java 9添加了一些次要功能和修复.
    • 许多java.time功能都向后移植到Java 6&中.7在> ThreeTen-Backport 中./li>
    • > ThreeTenABP 项目适应了<专门用于Android的em> ThreeTen-Backport (上面提到).
    • 请参阅 如何使用ThreeTenABP… .
    • The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
    • See How to use ThreeTenABP….

    > ThreeTen-Extra 项目扩展了java.time与其他班级.该项目为将来可能在java.time中添加内容提供了一个试验场.您可能会在这里找到一些有用的类，例如 间隔 ， 年周" ， YearQuarter 和更多

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