@Override
    public int compareTo(DateTimeStamp dateTimeStamp) {
        return  comparator.compare(this,dateTimeStamp);
    }
@Test
    void compareWithNullDates() {
        DateTimeStamp stamp1 = new DateTimeStamp((String)null, 100);
        DateTimeStamp stamp2 = new DateTimeStamp((String)null, 200);
        DateTimeStamp stamp3 = new DateTimeStamp((String)null, 100);
        assertTrue(stamp1.compareTo(stamp2) < 0);
        assertTrue(stamp1.compareTo(stamp3) == 0);
        assertTrue(stamp2.compareTo(stamp3) > 0);
    }