DateTimeFormatter exception parsing its own print result [duplicate]

Question

I don't understand something, I have this code :

DateTimeFormatter fmt = DateTimeFormatter.ofPattern("yyyyMMddHHmmssSSS");
System.out.println(LocalDateTime.parse(LocalDateTime.now().format(fmt), fmt));

This generate and exception :

Exception in thread "main" java.time.format.DateTimeParseException: Text '20200605102607066' could not be parsed at index 0
    at java.time.format.DateTimeFormatter.parseResolved0(DateTimeFormatter.java:1949)
    at java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1851)
    at java.time.LocalDateTime.parse(LocalDateTime.java:492)
    at Test.main(AccountPasswordHistoryTypeHandler.java:102)

But if I change the pattern to have a separator between date part and time part : "yyyyMMdd_HHmmssSSS" it works as expected.

Why is a formatter can't parse its own result ?

Fishback

It works fine with me, what java version you are using? – Vaal

check also the ideone demo – Vaal

I am using jdk 1.8u251 – Prurient

@Sweeper sorry, I didn't see this post. – Prurient

Answer 1

It is a bug in Java8 check this :

JDK-8031085 : DateTimeFormatter won't parse dates with custom format "yyyyMMddHHmmssSSS"

It was fixed in the new version.

Vaal

Thanks a lot, I will use the workaround. – Prurient

or make an upgrade to your JDK @Fishback there are many bugs fixed and many other features – Vaal

It is more than 2 years than I want to do so :( maybe at the end of the year I will succeed to make the higher ups understand. – Prurient