FULL PRODUCT VERSION :
java version "1.8.0_51"
Java(TM) SE Runtime Environment (build 1.8.0_51-b16)
Java HotSpot(TM) 64-Bit Server VM (build 25.51-b03, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
14.5.0 Darwin Kernel Version 14.5.0: Wed Jul 29 02:26:53 PDT 2015; root:xnu-2782.40.9~1/RELEASE_X86_64 x86_64

A DESCRIPTION OF THE PROBLEM :
Can parse a LocalDateTime using the following pattern: "yyyyMMddHHmmssSSS"
However this pattern works "yyyyMMddHHmmss.SSS" 

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Try parsing a string in the "yyyyMMddHHmmssSSS" format using:
LocalDateTime.parse("20150910121314987", DateTimeFormatter.ofPattern("yyyyMMddHHmmssSSS"))

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
no exception thrown and date successfully parsed
ACTUAL -
DateTimeParseException is thrown
Exception in thread "main" java.time.format.DateTimeParseException: Text '20150921165941914' could not be parsed at index 0
	at java.time.format.DateTimeFormatter.parseResolved0(DateTimeFormatter.java:1947)
	at java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1849)
	at java.time.LocalDateTime.parse(LocalDateTime.java:492)
	at TestLocalDataTimeFormat.main(TestLocalDataTimeFormat.java:11)

ERROR MESSAGES/STACK TRACES THAT OCCUR :
Exception in thread "main" java.time.format.DateTimeParseException: Text '20150921165941914' could not be parsed at index 0
	at java.time.format.DateTimeFormatter.parseResolved0(DateTimeFormatter.java:1947)
	at java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1849)
	at java.time.LocalDateTime.parse(LocalDateTime.java:492)

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.time.format.DateTimeFormatter;
import java.time.LocalDateTime;

public class TestLocalDataTimeFormat {

  public static void main(String[] args) {
      LocalDateTime now = LocalDateTime.now();
      DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMddHHmmssSSS");
      String date = formatter.format(now);
      System.out.println("date to parse: "+now);
      LocalDateTime.parse(date, formatter); // throws an exception
  }

}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
use the following format (mind the '.'): "yyyyMMddHHmmss.SSS"

LocalDateTime.parse("20150910121314987", DateTimeFormatter.ofPattern("yyyyMMddHHmmss.SSS"))

or alternatively use jodatime library