date to string using optional in java code example

Example: java parse date with optional timezone

public class DateFormatTest {

    private final DateTimeFormatter formatter = DateTimeFormatter.ofPattern(
            "yyyy-MM-dd[[ ]['T']HH:mm[:ss][XXX]]");

    private TemporalAccessor parse(String v) {
        return formatter.parseBest(v,
                                   ZonedDateTime::from,
                                   LocalDateTime::from,
                                   LocalDate::from);
    }

    @Test public void testDateTime1() {
        assertEquals(LocalDateTime.of(2014, 9, 23, 14, 20, 59),
                     parse("2014-09-23T14:20:59"));
    }

    @Test public void testDateTime2() {
        assertEquals(LocalDateTime.of(2014, 9, 23, 14, 20),
                     parse("2014-09-23 14:20"));
    }

    @Test public void testDateOnly() {
        assertEquals(LocalDate.of(2014, 9, 23), parse("2014-09-23"));
    }

    @Test public void testZonedDateTime() {
        assertEquals(ZonedDateTime.of(2014, 9, 23, 14, 20, 59, 0,
                                      ZoneOffset.ofHoursMinutes(10, 30)),
                     parse("2014-09-23T14:20:59+10:30"));
    }

}