Weekend query

This example is a custom TemporalQuery that will determine if a date is a weekend date. A weekend date is to be considered Saturday or Sunday day of week. Implementing the TemporalQuery interface with the queryFrom(TemporalAccessor) method allows for a way to extract information from a temporal object. The queryFrom method compares the passed-in date against the DayOfWeek and returns TRUE if the day of the week is SATURDAY or SUNDAY else returning false.

Setup

public class WeekendQuery implements TemporalQuery<Boolean> {

    /* (non-Javadoc)
     * @see java.time.temporal.TemporalQuery#queryFrom(java.time.temporal.TemporalAccessor)
     */
    @Override
    public Boolean queryFrom(TemporalAccessor date) {

        int dayOfWeekNumber = date.get(ChronoField.DAY_OF_WEEK);
        DayOfWeek dayOfWeek = DayOfWeek.of(dayOfWeekNumber);

        if (dayOfWeek == DayOfWeek.SATURDAY || dayOfWeek == DayOfWeek.SUNDAY) {
            return Boolean.TRUE;
        } else {
            return Boolean.FALSE;
        }
    }
}

Weekend query

@Test
public void check_if_date_is_weekend () {

    LocalDate date = LocalDate.of(2014, 02, 02); // Sunday

    Boolean workDay = date.query(new WeekendQuery());

    assertTrue(workDay);
}

Use query with lambda

@Test
public void filter_dates_by_weekend () {

    List<LocalDate> randomDays = Lists.newArrayList(
            LocalDate.of(2014, Month.FEBRUARY, 16), // Sunday
            LocalDate.of(2014, Month.APRIL, 19), // Saturday
            LocalDate.of(2014, Month.MAY, 30), // Friday
            LocalDate.of(2014, Month.DECEMBER, 12), // Friday
            LocalDate.of(2014, Month.DECEMBER, 17) // Wednesday
            );

    // filter weekend days 
    List<LocalDate> weekendDays = randomDays
            .stream()
            .filter(p -> p.query(new WeekendQuery()))
            .collect(Collectors.toList());

    assertEquals(2, weekendDays.size());
}