将字符串解析为本地日期不使用所需的世纪 [英] Parsing string to local date doesn't use desired century

问题描述

我正在使用这个 DateTimeFormatter:

DateTimeFormatter.ofPattern("ddMMYY")

我想解析字符串 150790 并且出现此错误:

无法从 TemporalAccessor 获取 LocalDate:{DayOfMonth=15, MonthOfYear=7, WeekBasedYear[WeekFields[MONDAY,4]]=2090}，java.time.format.Parsed 类型的 ISO

显然，我想获得以下 TemporalAccessor:

{DayOfMonth=15, MonthOfYear=7, WeekBasedYear=1990}

你知道为什么我得到的是 2090 年而不是 1990 年吗?

感谢您的帮助

解决方案

由于这个问题实际上是关于新的 java.time-package 而不是 SimpleDateFormat 我将引用以下内容相关部分:

<块引用>

Year:字母的数量决定了下面的最小字段宽度使用哪种填充.如果字母数是两个，则减少使用两位数形式.对于打印，这会输出最右边的两个数字.对于解析，这将使用基值 2000 进行解析，结果是 2000 年到 2099 年(含)范围内的一年.

我们看到 Java-8 使用范围 2000-2099 的默认值，而不是像 SimpleDateFormat 范围 -80 年到 +20 年(相对于今天).>

如果要配置它，则必须使用 appendValueReduced().这是以一种不方便的方式设计的，但可能，请参阅此处:

String s = "150790";//基本范围为 2000-2099 的旧代码日期时间格式器 dtf1 =new DateTimeFormatterBuilder().appendPattern("ddMMyy").toFormatter();System.out.println(dtf1.parse(s));//2090-07-15//基本范围为 1935-2034 的改进代码日期时间格式器 dtf2 =new DateTimeFormatterBuilder().appendPattern("ddMM").appendValueReduced(ChronoField.YEAR, 2, 2, Year.now().getValue() - 80).toFormatter();System.out.println(dtf2.parse(s));//1990-07-15

顺便说一下，如果您真的想要基于周的年份，那么您必须使用 Y 而不是 y 或适当的字段 IsoFields.WEEK_BASED_YEAR.关于您没有任何其他与周相关的字段这一事实，我假设是正常的日历年，而不是基于周的.

I am using this DateTimeFormatter:

DateTimeFormatter.ofPattern("ddMMYY")

I want to parse the string 150790 and I got this error:

Unable to obtain LocalDate from TemporalAccessor: {DayOfMonth=15, MonthOfYear=7, WeekBasedYear[WeekFields[MONDAY,4]]=2090},ISO of type java.time.format.Parsed

Obviously, I want to get the following TemporalAccessor:

{DayOfMonth=15, MonthOfYear=7, WeekBasedYear=1990}

Do you know why I got the year 2090 instead of 1990?

Thanks for your help

解决方案

Since this question is really about new java.time-package and NOT SimpleDateFormat I will cite following relevant section:

Year: The count of letters determines the minimum field width below which padding is used. If the count of letters is two, then a reduced two digit form is used. For printing, this outputs the rightmost two digits. For parsing, this will parse using the base value of 2000, resulting in a year within the range 2000 to 2099 inclusive.

We see that Java-8 uses the range 2000-2099 per default, not like SimpleDateFormat the range -80 years until +20 years relative to today.

If you want to configure it then you have to use appendValueReduced(). This is designed in an inconvenient way, but possible, see here:

String s = "150790";

// old code with base range 2000-2099
DateTimeFormatter dtf1 = 
  new DateTimeFormatterBuilder().appendPattern("ddMMyy").toFormatter();
System.out.println(dtf1.parse(s)); // 2090-07-15

// improved code with base range 1935-2034
DateTimeFormatter dtf2 = 
  new DateTimeFormatterBuilder().appendPattern("ddMM")
  .appendValueReduced(
    ChronoField.YEAR, 2, 2, Year.now().getValue() - 80
  ).toFormatter();
System.out.println(dtf2.parse(s)); // 1990-07-15

By the way, if you really want week-based years then you have to use Y instead of y or the appropriate field IsoFields.WEEK_BASED_YEAR. Regarding the fact that you don't have any other week-related fields I would assume the normal calendar year, not the week-based one.

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