package zy813ture;

public class MyLinkedQueue1 {

private Node head;

private Node last = head = new Node();//初始化可以设定默认值，形式固定

// private int size;

private class Node {

private Object data;

private Node next;

}

public MyLinkedQueue1() {

// last = head = new Node();

// last=head;

}

public boolean offer(Object element) {// 将指定的元素插入此队列

if (element == null) {

throw new NullPointerException();

}

// 1

Node node = new Node();

node.data = element;

// 2

last.next = node;

// 3

last = node;

// size++;

return true;

}

public Object peek() {// 获取不移除此队列的头，如果此队列为空，则返回 null。

if (head.next == null) {

return null;

}

return head.next.data;

}

public Object poll() {// 获取并移除此队列的头，如果此队列为空，则返回 null。

if (head.next == null) {

return null;

}

//1

Node node = head;

//2

head= head.next;

//3

//node= null;

node =null;

return head.data;

}

public static void main(String []args){

MyLinkedQueue1 me= new MyLinkedQueue1();

me.offer("ab1");

me.offer("ab2");

me.offer("ab3");

me.offer("ab4");

me.offer("ab5");

//System.out.println(me.peek());

System.out.println(me.poll());//ab1 null

System.out.println(me.poll());//

//System.out.println(me.peek());

//System.out.println(me.peek());

}

}