### Question:
Day implements Comparable { @Override public int hashCode() { return dayStr.hashCode(); } Day(String dayStr);  Day(String dayStr, List<Integer> hours); String getDayStr(); List<Integer> getHours(); static List<Day> buildSortedDays(List<Range> ranges); static Set<String> getDayString(Set<Day> days); static Set<String> getDayStringTreated(Set<Day> days, String toBeRemoved); @Override int hashCode(); @Override boolean equals(Object dayObject); static String treatDayStr(String dayStr); @Override int compareTo(Object o);  }### Answer:
@Test public void testHashCode() { String dayStr = "20180105"; Day day = new Day(dayStr); assertNotNull(day.hashCode()); }