### Question:
Hour extends RegularTimePeriod implements Serializable { @Override public long getSerialIndex() { return this.day.getSerialIndex() * 24L + this.hour; } Hour();  Hour(int hour, Day day);  Hour(int hour, int day, int month, int year);  Hour(Date time);  Hour(Date time, TimeZone zone, Locale locale); int getHour(); Day getDay(); int getYear(); int getMonth(); int getDayOfMonth(); @Override long getFirstMillisecond(); @Override long getLastMillisecond(); @Override void peg(Calendar calendar); @Override RegularTimePeriod previous(); @Override RegularTimePeriod next(); @Override long getSerialIndex(); @Override long getFirstMillisecond(Calendar calendar); @Override long getLastMillisecond(Calendar calendar); @Override boolean equals(Object obj); @Override String toString(); @Override int hashCode(); @Override int compareTo(TimePeriod o1); static Hour parseHour(String s); static final int FIRST_HOUR_IN_DAY; static final int LAST_HOUR_IN_DAY; }### Answer:
@Test public void testGetSerialIndex() { Hour h = new Hour(1, 1, 1, 2000); assertEquals(876625L, h.getSerialIndex()); h = new Hour(1, 1, 1, 1900); assertEquals(49L, h.getSerialIndex()); }