如何使用SimpleDateFormat解析多种格式的日期 [英] How to parse dates in multiple formats using SimpleDateFormat

问题描述

我正在尝试解析文档中出现的一些日期。看来用户已经输入了相似但不完全相同的格式。

这里是格式：
9/09
9/2009
09/2009
9/1/2009
9-1-2009

最好的方法是尝试解析所有这些？这些似乎是最常见的，但我猜是挂起我的是，如果我有一个M / yyyy的模式，永远在MM / yyyy之前抓到我必须设置我的try / catch块以最严格的限制性方式嵌套最少限制？似乎它肯定会采取大量的代码重复来获得这个权利。

解决方案

您需要为每个对象使用不同的 SimpleDateFormat 不同的模式也就是说，您不需要许多不同的，感谢这个：

编号：对于格式化，模式字母数是最小位数，较短的数字被零填充到这个数量。为了解析，模式字母的数量将被忽略，除非需要分隔两个相邻的字段。

所以，你需要这些格式：

• M / y（涵盖 9/09 ， 9/2009 和 09/2009 ）


• M / d / y（涵盖 9/1/2009 ）


• Mdy（涵盖 9-1-2009 ）未测试）：

    // ... 
   String [] formatStrings = {M / y，M / d / y Mdy}; 
   // ... 
   
  日期tryParse（String dateString）
   {
   for（String formatString：formatStrings）
   {
   try 
   {
  返回新的SimpleDateFormat（formatString）.parse（dateString）; 
  } 
   catch（ParseException e）{} 
  } 
   
  返回null; 
  } 
    

  
  

  I am trying to parse some dates that are coming out of a document. It would appear users have entered these dates in a similar but not exact format.

  here are the formats: 9/09 9/2009 09/2009 9/1/2009 9-1-2009

  What is the best way to go about trying to parse all of these? These seem to be the most common, but I guess what is hanging me up is that if i have a pattern of "M/yyyy" wont that always catch before "MM/yyyy" Do I have to set up my try/catch blocks nested in a least restrictive to most restrictive way? it seems like it sure is going to take a lot of code duplication to get this right.

  解决方案

  You'll need to use a different SimpleDateFormat object for each different pattern. That said, you don't need that many different ones, thanks to this:

  Number: For formatting, the number of pattern letters is the minimum number of digits, and shorter numbers are zero-padded to this amount. For parsing, the number of pattern letters is ignored unless it's needed to separate two adjacent fields.

  So, you'll need these formats:

  • "M/y" (that covers 9/09, 9/2009, and 09/2009)
  • "M/d/y" (that covers 9/1/2009)
  • "M-d-y" (that covers 9-1-2009)

  So, my advice would be to write a method that works something like this (untested):

  // ...
  String[] formatStrings = {"M/y", "M/d/y", "M-d-y"};
  // ...
  
  Date tryParse(String dateString)
  {
      for (String formatString : formatStrings)
      {
          try
          {
              return new SimpleDateFormat(formatString).parse(dateString);
          }
          catch (ParseException e) {}
      }
  
      return null;
  }
  

  这篇关于如何使用SimpleDateFormat解析多种格式的日期的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！