DefaultFormatter implements Formatter { @Override public String getDayName(@NonNull LocalDate date) { return date.toString(dayFormatter); } DefaultFormatter();  DefaultFormatter(@NonNull String dayPattern, @NonNull String weekPattern, @NonNull String monthPattern); @Override String getDayName(@NonNull LocalDate date); @Override String getHeaderText(@CalendarType int type, @NonNull LocalDate from, @NonNull LocalDate to);  }
@Test public void testGetDayName() throws Exception { String dayName = formatter.getDayName(new LocalDate(2015, 4, 26)); assertEquals("Sun", dayName); }