用非顺序映像实现队列

package myqueue;

import mylinkedlist.MyLinkedList;

import java.util.NoSuchElementException;

public class myQueue <E>{
    private Node head;
    private Node end;
    private int size;

    private static class Node<E>{
        public Node next;
        public Node prev;
        E val;
        public Node(E val){
            this.val = val;
        }
        public Node(Node prev,E val,Node next){
            this.val = val;
            this.next = next;
            this.prev = prev;
        }
    }

    public myQueue(){
        head = new Node(null);
        end = new Node(null);
        head.next = end;
        end.prev = head;

    }
    public void enque(E e){
        Node nodeToEnque = new Node(end.prev,e,end);
        end.prev.next = nodeToEnque;
        end.prev = nodeToEnque;
        size++;
    }
    public E deque(){
        //先判断是否队空
        if(isEmpty()){
            throw new NoSuchElementException();
        }
        Node nodeToRemove = head.next;
        head.next = head.next.next;
        nodeToRemove.next.prev = head;
        size--;
        return (E)nodeToRemove.val;

    }

    public boolean isEmpty() {
        return size==0;
    }
    public int size(){
        return size;
    }
    public E peek(){
        return (E)head.next.val;
    }
    public String toString(){
        StringBuilder sb = new StringBuilder("[");
        Node x =head.next;
        while(x!=end){
            sb.append(x.val).append(", ");
            x =x.next;
        }
        if(size !=0) sb.delete(sb.length()-2,sb.length());
        return sb.append("]").toString();
    }

}

package myqueue;

public class TestMyQueue {
    public static void main(String args[]){
        myQueue<Integer> que = new myQueue();
        System.out.println("队列空吗？"+que.isEmpty());
        que.enque(1);
        que.enque(2);
        que.enque(3);
        que.enque(4);
        System.out.println(que.toString()+"，长度位："+que.size());
        System.out.println("出队："+que.deque());
        System.out.println("队列空吗？"+que.isEmpty());


    }
}