### Question:
DateUtil { public static Date addDate(int field, int amount) { return addDate(null, field, amount); }  static Date addDate(int field, int amount); static Date addDate(Date date, int field, int amount); static String format(Date date, String pattern); static Date getDayBegin(Date date); static Date getDayBegin(); static Date getDayEnd(Date date); static Date getDayEnd(); static void setCalender(Calendar calendar, int hour, int minute, int second, int milliSecond); static boolean isBetween(Date beginTime, Date endTime);  }### Answer:
@Test public void testAddDate() { Assert.assertNull(DateUtil.addDate(0, 0)); Assert.assertEquals(new Date(1_778_410_800_000L), DateUtil.addDate( new Date(1_515_585_600_000L), 2, 100)); }