队列实现 java版本

public class Queue<T> implements Iterable<T>{
private class Node{//定义节点类
T item;
Node nextNode;
}
private Node firstNode;
private Node lastNode;
private int N;

public boolean isEmpty(){
return firstNode == null;
}

public int size(){
return N;
}

public void enQueue(T item){// 队尾插入新节点
Node oldNode = lastNode;
lastNode = new Node();
if (isEmpty()) {
firstNode = lastNode;
}
else{
oldNode.nextNode = lastNode;
}
N++;
}

public T deQueue(){// 队首插入新节点
T item = firstNode.item;
firstNode = firstNode.nextNode;
if(isEmpty())
lastNode = null;
N--;
return item;
}
// 以下实现Iterator 接口 ，方便迭代输出 ， 可选实现
public Iterator iterator(){
return new queueIterator();
}

private class queueIterator implements Iterator<T>{
Node iteratorNode = firstNode;
@Override
public boolean hasNext() {
return iteratorNode != null;
}

@Override
public T next() {
T item = (T) iteratorNode.item;
iteratorNode = iteratorNode.nextNode;
return item;
}

}

}