[SOLVED] Is this additional check for parsing a string to LocalDate object necessary?

Is this additional check for parsing a string to LocalDate object necessary?

I was writing some tests for some legacy code that validates a user's date of birth. I encounter the following method in the class. My doubt is that whether the if statement in the try block is necessary. From my understanding, if the parse function returns a LocalDate object successfully, then date.toString() should always equal to the input dobstr, and there's no need to do an additional check. Am I missing anything? I could not think of any case that we need this extra check. Please help. Thanks!

private LocalDate format(String dobStr) throws Exception {
        LocalDate date = null;
        try {
            date = LocalDate.parse(dobStr, DateTimeFormatter.ISO_DATE);
            if (!dobStr.equals(date.toString())) {
                 throw new DateTimeParseException("some message");
            }
        }
        catch (DateTimeParseException ex) {
            throw ex;
        }
        return date;
}

this is what I found in the source code for DateTimeFormatter.ISO_DATE

public static final DateTimeFormatter ISO_DATE;
static {
    ISO_DATE = new DateTimeFormatterBuilder()
            .parseCaseInsensitive()
            .append(ISO_LOCAL_DATE)
            .optionalStart()
            .appendOffsetId()
            .toFormatter(ResolverStyle.STRICT, IsoChronology.INSTANCE);
}

Solution

The only reason that I could see for doing a toString() check would be to avoid lenient issue: the parser may be lenient and try to interpret wrong values (for example: 2020-12-32 could be interpreted as 2021-01-01).

DateFormat allows the parser to be lenient
The same behaviour is offered by DateTimeFormatter and the default value is ResolverStyle.SMART.

If you want to remove it, you should check if DateTimeFormatter.ISO_DATE is ResolverStyle.STRICT by default or not. Assuming it is not STRICT by default, your code could be:

private LocalDate format(String dobStr) throws Exception {
  return LocalDate.parse(dobStr, DateTimeFormatter.ISO_DATE.withResolverStyle(ResolverStyle.STRICT));
}