A DESCRIPTION OF THE REQUEST :
When parse large text file using method a, performance is bad!
And the workaround code method b is not elegant.

private LocalDateTime a(String time) {
    return LocalDateTime.parse(time, ofPattern("yyyyMMddHHmmss"));
}

// workaround code
private LocalDateTime b(String time) {
    int year = Integer.valueOf(time.substring(0, 4));
    int month = Integer.valueOf(time.substring(4, 6));
    int day = Integer.valueOf(time.substring(6, 8));
    int hour = Integer.valueOf(time.substring(8, 10));
    int minute = Integer.valueOf(time.substring(10, 12));
    int sec = Integer.valueOf(time.substring(12));
    return LocalDateTime.of(year, month, day, hour, minute, sec);
}

JUSTIFICATION :
Performance is important !

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
improved performance
ACTUAL -
bad performance

CUSTOMER SUBMITTED WORKAROUND :
private LocalDateTime b(String time) {
    int year = Integer.valueOf(time.substring(0, 4));
    int month = Integer.valueOf(time.substring(4, 6));
    int day = Integer.valueOf(time.substring(6, 8));
    int hour = Integer.valueOf(time.substring(8, 10));
    int minute = Integer.valueOf(time.substring(10, 12));
    int sec = Integer.valueOf(time.substring(12));
    return LocalDateTime.of(year, month, day, hour, minute, sec);
}