### Question:
WallClock implements Clock<WallClockTimestamp> { @Override public WallClockTimestamp getTime() { return new WallClockTimestamp(); }  @Override WallClockTimestamp getTime(); @Override String toString();  }### Answer:
@Test public void testWallClock() throws Exception { WallClock clock = new WallClock(); WallClockTimestamp time = clock.getTime(); assertNotNull(time); Thread.sleep(5); assertTrue(clock.getTime().unixTimestamp() > time.unixTimestamp()); }
@Test public void testWallClock() throws Exception { final WallClock clock = new WallClock(); final WallClockTimestamp time = clock.getTime(); assertNotNull(time); Thread.sleep(5); assertTrue(clock.getTime().unixTimestamp() > time.unixTimestamp()); }