public Animal Dequeue() { if (first == null) return null; Animal returned = first; first = first.next; if (first == null) last = null; return returned; }
public void Enqueue(Animal a) { if (last == null) { last = a; first = a; return; } last.next = a; last = last.next; }
public AnimalQueue() { first = null; last = null; }
public Animal() { timeArrived = DateTime.Now; next = null; }