thinking java

public class CrossContainerIteration{
    public static void display(Iterator<Pet> it){
            while(it.hasNext()){
                    Pet tmp = it.next();
                    System.out.print("输出："+tmp.id());
                }
        }
    public static void main(String[] args){
            ArrayList<Pet> pets = Pets.arrayList(8);
            LinkedList<Pet> petsLL = new LinkedList<Pet>(pets);
            HashSet<Pet> petsHS = new HashSet<Pet>(pets);
            TreeSet<Pet> petsTS = new TreeSet<Pet>(pets);
            display(pets.iterator());
            display(petsLL.iterator());
            display(petsHS.iterator());
            display(petsTS.iterator());
        }
    }