static void Main(string[] args) {
CountdownWatch watch = new CountdownWatch();
Timer timer = new Timer();
Alarm alarm = new Alarm();
Console.WriteLine("First call");
watch.StartCount(5);
Thread.Sleep(6);
timer.Register(watch);
Console.WriteLine("\nSecond call");
watch.StartCount(5);
Thread.Sleep(6);
alarm.Register(watch);
Console.WriteLine("\nThird call");
watch.StartCount(5);
Thread.Sleep(6);
timer.UnRegister(watch);
Console.WriteLine("\nFourth call");
watch.StartCount(5);
Thread.Sleep(6);
alarm.UnRegister(watch);
Console.WriteLine("\nFifth call");
watch.StartCount(5);
Thread.Sleep(6);
timer.UnRegister(watch);
alarm.Register(watch);
Console.WriteLine("\nSixth call");
watch.StartCount(5);
Thread.Sleep(6);
alarm.UnRegister(watch);
Console.ReadLine();
}
public void Register(CountdownWatch watch) {
if(watch == null)
throw new ArgumentNullException(nameof(watch));
watch.FinishCountdown += TimerCall;
}
