LocalDateTime.parse(yyyMMddHHmmssSSS, DateTimeFormatter.ofPattern("yyyyMMddHHmmssSSS") error

Question

Why doesn't it work? ... 1) is works, but 2) occurs DateTimeParseException.

# 1

DateTimeFormatter formatter1 = DateTimeFormatter.ofPattern("yyyyMMddHHmmss.SSS");
LocalDateTime dt1 = LocalDateTime.parse("20211211134321.221", formatter1);

# 2

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMddHHmmssSSS");
LocalDateTime dt = LocalDateTime.parse("20211211134321221", formatter);

Answer 1

Bug, fixed in Java 9+

Per the comments, it seems that such code runs successfully in some earlier versions of Java 8 but fails in other later versions of Java 8.

Apparently due to a bug, JDK-8031085, fixed in Java 9+.

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Here is my reformatted version of your code.

DateTimeFormatter fx = DateTimeFormatter.ofPattern( "yyyyMMddHHmmss.SSS" ); 
LocalDateTime x = LocalDateTime.parse( "20211211134321.221" , fx );
System.out.println( "x = " + x ) ;

DateTimeFormatter fy = DateTimeFormatter.ofPattern( "yyyyMMddHHmmssSSS" ); 
LocalDateTime y = LocalDateTime.parse( "20211211134321221" , fy );
System.out.println( "y = " + y ) ;

When run in Java 12, as seen on IdeOne.com.

x = 2021-12-11T13:43:21.221
y = 2021-12-11T13:43:21.221