### Question:
TimeDuration { public static String toSecondString(Duration duration){ return duration.getSeconds() + "." + format.format(duration.getNano()); } private  TimeDuration(); static Duration createDuration(long sec, int nanoSec); static Duration ofHours(double hour); static Duration ofMinutes(double min); static Duration ofSeconds(double sec); static Duration ofHertz(double hz); static int dividedBy(Duration dividendDuration, Duration divisorDuration); static double toSecondsDouble(Duration duration); static String toSecondString(Duration duration);  }### Answer:
@Test public void toString1() { Duration duration = Duration.ofMillis(10); assertThat(TimeDuration.toSecondString(duration), equalTo("0.010000000")); }