static void Main(string[] args)
{
Countdown countdown = new Countdown(10, "Hello, world!");
CountdownDisplay countdownDisplay = new CountdownDisplay();
countdownDisplay.Subscribe(countdown);
CountdownDisplay countdownDisplay2 = new CountdownDisplay();
countdownDisplay2.Subscribe(countdown);
countdown.Start();
}
public void Subscribe(Countdown countdown)
{
countdown.CountdownComplete += PrintCountdownComplete;
}