### Question:
DateUtil { public static Date getFirstDayInMonth(Date date){ Calendar calendar = Calendar.getInstance(); if(date != null){ calendar.setTime(date); } calendar.set(Calendar.DAY_OF_MONTH, 1); calendar.set(Calendar.HOUR_OF_DAY, 0); calendar.set(Calendar.MINUTE, 0); calendar.set(Calendar.SECOND, 0); return calendar.getTime(); }  static String getYearMonth(Date date); static String formateYearMonthDay(Date date); static Date parseYearMonthDay(String timeStr, Date defaultValue); static String formateDateTime(Date date); static Date parseDateTime(String timeStr, Date defaultValue); static final int getCurrentHour(); static final int getLastHour(); static final int getNextHour(); static Date getFirstDayOfCurMonth(); static Date getFirstDayInMonth(Date date); static Date getFirstDayInMonth(int month); static boolean isCurrentMonth(Date date);  }### Answer:
@Test public void testGetFirstDayInMonth() { assertEquals(new Date(1320076800282L), DateUtil.getFirstDayInMonth(new Date(1322197921282L))); }