SimpleDateFormat vs DateTimeFormatter

Question

I have a use case where I have to compare 2 string dates such as

final SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
 System.out.println(dateFormat.parse("2019-07-07").compareTo(dateFormat.parse("2019-07-07 23:59:59"))>0);

The above statement using SimpleDateFormat works perfectly fine, now I try doing it using DateTimeFormatter

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
        System.out.println( LocalDate.parse("2019-07-07", formatter).compareTo(LocalDate.parse("2019-07-07 23:59:59", formatter))>=0);

This fails with exception:-

Exception in thread "main" java.time.format.DateTimeParseException: Text '2019-07-07 23:59:59' could not be parsed, unparsed text found at index 10
    at java.time.format.DateTimeFormatter.parseResolved0(DateTimeFormatter.java:1952)
    at java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1851)
    at java.time.LocalDate.parse(LocalDate.java:400)
    at com.amazon.payrollcalculationengineservice.builder.EmployeeJobDataBuilder.main(EmployeeJobDataBuilder.java:226)

How can I avoid this using DateTimeFormatter, the Strings which I pass as input can be in any format like yyyy-mm-dd or yyyy-mm-dd hh:mm:ss , I dont want to write explicitly checks for format , so can I do using DateTimeFormatter as I am able to do this using the SimpleDateFormat library.

Answer 1

You can use [] to specify an optional part of the pattern:

DateTimeFormatter.ofPattern("yyyy-MM-dd[ HH:mm:ss]");

Alternatively, use the overload of parse that takes a ParsePosition, which won't try to parse the entire string if not necessary.

var formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
var localDate = LocalDate.from(formatter.parse("2019-07-07 23:59:59", new ParsePosition(0)))