Java 8 LocalDateTime dropping 00 seconds value when parsing date string value with 00 seconds like "2018-07-06 00:00:00"

Feature, not a bug

You are seeing the documented behavior of the particular DateTimeFormatter used by the LocalDateTime::toString method.

Excerpt, my emphasis:

The output will be one of the following ISO-8601 formats:

uuuu-MM-dd'T'HH:mm

uuuu-MM-dd'T'HH:mm:ss

uuuu-MM-dd'T'HH:mm:ss.SSS

uuuu-MM-dd'T'HH:mm:ss.SSSSSS

uuuu-MM-dd'T'HH:mm:ss.SSSSSSSSS

The format used will be the shortest that outputs the full value of the time where the omitted parts are implied to be zero.

If you want other behavior when generating a String to represent the value of you LocalDateTime, use a different DateTimeFormatter and pass it to LocalDateTime::format.

String output = myLocalDateTime.format( someOtherFormatter ) ;

The LocalDateTime has no “format” as it is not text. It is the job of the DateTimeFormatter to parse or generate String objects of a particular format.

You need to format your date with the proper formatter instead of using default one by calling toString().

final String lexicalDate = localDateTime.format(dateTimeFormatter);