package Test;

public class LinkedListQueue {

	public static void main(String[] args) {
		// TODO Auto-generated method stub

		Queue <Integer> queue=new Queue<Integer>();
		queue.add(1);
		queue.add(2);
		queue.add(3);
		queue.add(4);
		queue.add(5);
		System.out.println(queue.pop());
		System.out.println(queue.pop());
		System.out.println(queue.pop());
		System.out.println(queue.pop());
		System.out.println(queue.pop());
	}

}
class Node<E>{
	public Node(E data2) {
		this.data=(E) data2;
	}
		// TODO Auto-generated constructor stub
	public E data;
	public Node<E> next=null;
	
	
}
class Queue<E>{
	private Node<E> Head=null;
	private Node<E> tail=null;
	
	public boolean isEmpty(){
		boolean a=(Head==null&&tail==null);
		return a;
	}
	
	
	public void add(E data) {
		Node <E> newNode=new Node<E>(data);
		if(Head==null&&tail==null)
		{
			Head=tail=newNode;
			//佇列是空的
		}
		else {
			tail.next=newNode;
			tail=newNode;//新增
		}
	}
	public E pop()//先進先出
	{
		if(this.isEmpty())
		{
			return null;//這個是空的
		}
		E data=Head.data;
		Head=Head.next;
		return data;//返回出棧的元素
	}
	public int size() {
		Node<E>temp=Head;
		int n=0;
		while(temp!=null)
		{
			n++;
			temp=temp.next;
		}
		return n;
	}
}