java.time equivalent of Joda-Time `withTimeAtStartOfDay`? (get first moment of the day)

Question

In the Joda-Time library, the DateTime class offers a method withTimeAtStartOfDay to get the first moment of the day. You might think of that moment as \"midnight\". That first

Answer 1

TemporalAdjuster

Every LocalTime is also a TemporalAdjuster, so if can be passed to the with() method of most temporal types and will update the time fields to match.

That is:

@Test
public void date_time_at_start_of_day() throws Exception {
    assertThat(LocalDateTime.parse("2015-05-22T12:27:00")
                            .with(LocalTime.MIDNIGHT),
               equalTo(LocalDateTime.parse("2015-05-22T00:00:00")));
    assertThat(OffsetDateTime.parse("2015-05-22T12:27:00+01:00")
                             .with(LocalTime.MIDNIGHT),
               equalTo(OffsetDateTime.parse("2015-05-22T00:00:00+01:00")));
    assertThat(ZonedDateTime.parse("2015-05-22T12:27:00+01:00[Europe/London]")
                            .with(LocalTime.MIDNIGHT),
               equalTo(ZonedDateTime.parse("2015-05-22T00:00:00+01:00[Europe/London]")));
}