双向队列

package MyJava2;

public class DuLinkQueue {
    class Node{
        private String data;
        private Node prve;
        private Node next;
        public Node(String data){
            this.data=data;
        }
    }
    private Node front;
    private Node rear;
    private int size=0;
    public DuLinkQueue(){
        front=null;
        rear=null;
    }
    public DuLinkQueue(String data){
        front=new Node(data);
        rear=front;
        size++;
    }
    public int len(){
        return size;
    }
    public void addAtHead(String data){//队首添加元素
        Node newNode=new Node(data);
        if(front==null){//若该链队列为空，则尾节点是新节点
            rear=newNode;
        }else {
            front.prve=newNode;
        }
        newNode.next=front;
        front=newNode;
        size++;
    }
    public void addAtTail(String data){//队尾添加元素
        Node newNode=new Node(data);
        if(front==null){//若该链队列为空，则头节点是新节点
            front=newNode;
        }else {
            rear.next=newNode;
        }
        newNode.prve=rear;
        rear=newNode;
        size++;
    }
    public String delAtHead(){//移除队首元素
        Node oldNode=front;
        front=oldNode.next;
        if(front!=null){//至少有两个节点
            front.prve=null;
        }else {
            rear=null;
        }size--;
        return oldNode.data;
    }
    public String delAtTail(){//移除队尾元素
        Node oldNode=rear;
        rear=oldNode.prve;
        if(rear!=null){
            rear.next=null;
        }else {
            front=null;
        }
        size--;
        return oldNode.data;
    }
    public boolean empty(){
        return size==0;
    }
    public void clear(){
        front=null;
        rear=null;
        size=0;
    }
    public String toString(){
        StringBuffer sb=new StringBuffer();
        Node current=front;
        for(;current!=null;current=current.next){
            sb.append(current.data+",");
        }return sb.toString();
    }

    public static void main(String[] args) {
        DuLinkQueue queue=new DuLinkQueue();
        queue.addAtHead("A");
        queue.addAtHead("1B");
        queue.addAtHead("1C");
        queue.addAtTail("B1");
        queue.addAtTail("C1");
        System.out.println(queue.toString());
        System.out.println(queue.delAtHead());
        System.out.println(queue.delAtTail());
        System.out.println(queue.toString());

    }

}