java DateTimeFormatter严格与宽松的意外行为

Question

我有一些text，只有在解析样式为Strict时才被DateTimeFormatter解析，而不是在Lenient时

这似乎与我的预期相反

例如：

String pattern = "ddMMyyHH:mm:ss";
String text = "02011104:21:32";

System.out.println(MessageFormat.format("Strict - {0}", new DateTimeFormatterBuilder().parseStrict().appendPattern(pattern).toFormatter().parse(text)));
System.out.println(MessageFormat.format("Lenient - {0}", new DateTimeFormatterBuilder().parseLenient().appendPattern(pattern).toFormatter().parse(text)));

输出：

Strict - {},ISO resolved to 2011-01-02T04:21:32
Exception in thread "main" java.time.format.DateTimeParseException: Text '02011104:21:32' could not be parsed at index 8

Answer 1

将此作为bug发布后-https://bugs.java.com/bugdatabase/view_bug.do?bug_id=JDK-8228353

我得到的答复如下：

According to DateTimeFormatterBuilder's spec, appendPattern("yy") translates to appendValueReduced(ChronoField.YEAR_OF_ERA, 2, 2000), where "2" applies both for with and maxWidth. In the method description, it reads:

For strict parsing, the number of characters allowed by width to maxWidth are parsed. For lenient parsing, the number of characters must be at least 1 and less than 10.

因此，在这种情况下，在严格模式下，只有“11”被读取为“yy”，然后用基值2000生成年份“2011”。但在宽松模式下，“yy”试图贪婪地读取“：”之前的内容，并生成年份“1104”，然后解析器抛出异常，试图用“HH”模式解析“：”