链表式队列JAVA实现

链表式队列JAVA实现：

public class LinkedQueue<E> {

      

      static class Node<E>{

            E item;

            

            Node<E> next;

            

            Node(E e) { item = e; }

      }

      

      private Node<E> head;//头节点

      

      private Node<E> last;//尾节点

      

      private int size;

      

      public boolean isEmpty(){

//          return head == null;

            return size == 0;

      }

      

      //入队

      public void enqueue(Node<E> node){

            last = last.next = node;

            last.next = head;

            size++;

      }

      

      //出队

      public E dequeue(){

            Node<E> n = head;

            Node<E> first = head.next;

            head = first;

            E e = n.item;

            n.item = null;

            size--;

            return e;

      }

      

      //获取大小

      public int size(){

            /*Node<E> tmp = head;

            int len = 0;

            while(tmp != null){

                  tmp = tmp.next;

                  len++;

            }

            return len;*/

            return size;

      }

      

      //放元素进链表队列

      public void offer(E e){

            Node<E> node = new Node<E>(e);

            if(isEmpty()){

                  head = node;

                  last = node;

            }

            enqueue(node);

            

      }

      

      //取出元素出链表队列

      public E poll(){

            E e = dequeue();

            return e;

      }

      

      //获取链表队列头元素

      public E peek(){

            if(isEmpty()){

                  return null;

            }

            return head.item;

      }

      public static void main(String[] args) {

            LinkedQueue<String> queue = new LinkedQueue<>();

        queue.offer("a");

        queue.offer("b");

        queue.offer("c");

        queue.offer("d");

        System.out.println("head =" + queue.head.item);

        System.out.println("head.next =" + queue.head.next.item);

        System.out.println("last =" + queue.last.item);

        System.out.println("last.next =" + queue.last.next.item);

       

        System.out.println(queue.size());

        System.out.println(queue.poll());

        System.out.println(queue.size());

        System.out.println(queue.poll());

        System.out.println(queue.size());

        System.out.println(queue.peek());

        System.out.println(queue.size());

        queue.offer("e");

        System.out.println(queue.size());

       

        System.out.println("head =" + queue.head.item);

        System.out.println("head.next =" + queue.head.next.item);

        System.out.println("last =" + queue.last.item);

        System.out.println("last.next =" + queue.last.next.item);

    }

      

}

闲来无事学习一下Queue相关知识，麻烦各位看看，有上面地方可以改进的~