java实现迭代遍历接口的队列（Queue）

<!-- lang: java -->
public class Queue<Item> implements Iterable<Item>{
private Node first;
private Node last;
private int N;
private class Node{
Item item;
Node next;
}
public boolean isEmpty(){ return first == null;}
public int size(){ return N;}
public void enqueue(Item item){
Node oldLast = last;
last = new Node();
last.item = item;
last.next = null;
if( isEmpty())
first = last;
else
oldLast.next = last;
N++;
}
public Item dequeue(){
Item item = first.item;
first = first.next;
if( isEmpty())
last = null;
N--;
return item;
}
public class AIterator<Item> implements Iterator<Item>{
private Node ifirst=first;
@Override
public boolean hasNext() {
return ifirst==null;
}
@Override
public Item next() {
Item item = ifirst.item;
Node first = ifirst.next;
return item;
}

@Override
public void remove() {
}
}
@Override
public Iterator<Item> iterator() {
return new AIterator();
}

}