[数据结构]-链表实现队列

[数据结构]-链表实现队列

如有问题，请指出呀。感谢。

 

 

package com.cn.jichu.day09;

public class LinkedQueue<E> {

    /**
     * 首节点
     */
    private Node head;
    /**
     * 尾节点
     */
    private Node tail;
    /**
     * 当前栈中元素个数
     */
    private int size;

    public LinkedQueue(){
        this.size = 0;
    }

    /**
     * 入列
     * @param e
     */
    public void enqueue(E e){
        Node node = new Node(e);
        if(head == null && tail == null){
            head = tail = node;
            size ++;
            return;
        }
        tail.next = node;
        tail = node;
        size ++;
    }

    /**
     * 出列
     * @return
     */
    public E dequeue(){
        if(head==null){
            throw  new IllegalArgumentException("当前队列无元素");
        }

        if(head.equals(tail)){
            System.out.println("head.equals(tail)");
            E e = head.data;
            head = tail = null;
            size --;
            return e;
        }

        E e = head.data;
        head = head.next;
        size --;
        return e;
    }

    /**
     * 获取队列中的元素个数
     * @return
     */
    public int getSize(){
        return size;
    }




    private class Node{
        private Node next;
        private E data;

        public Node(E data) {
            this.data = data;
        }
    }

    @Override
    public String toString(){
        StringBuilder ret = new StringBuilder();
        ret.append("queue  head[");
        Node node = head;
        while (node!=null){
            ret.append(node.data + "-->");
            node = node.next;
        }
        ret.append("null ] tail");
        return ret.toString();
    }

}