循环链表

package Myjava;

public class CircularLinkedList {
    private class Node{
        String data;
        Node next;
        public Node(){}
        public Node(String data,Node next){
            this.data=data;
            this.next=next;
        }
    }
    private Node header;
    private int size;

    public CircularLinkedList(){
        header=null;
    }
    public CircularLinkedList(String data){
        header=new Node(data,null);
        header.next=header;
        size++;
    }

    public void addAtTail(String data){//尾插
        Node node=new Node(data,null);
        if(header.next==header){
            header.next=node;
            node.next=header;
        }else{
            Node current=header;
            while(current.next!=header){
                current=current.next;
            }
            current.next=node;
            node.next=header;
        }
        size++;
    }

    public String getData(int index){
        return getNodeByIndex(index).data;
    }

    private Node getNodeByIndex(int index) {
        if(index<0||index>size-1){
            throw new IndexOutOfBoundsException("OutOfIndex");
        }
        Node current=header;
        for(int i=0;i<size&&current!=null;i++,current=current.next){
            if(index==i){
                return current;
            }
        }
        return null;
    }

    public String delNodeByIndex(int index){//删除指定索引处的节点
        if(index<0||index>size-1){
            throw new IndexOutOfBoundsException("OutOfIndex");
        }
        Node delNode=null;
        if(index==0){
            delNode=header;
            header=header.next;
        }else {
            Node prve=getNodeByIndex(index-1);
            delNode=prve.next;
            prve.next=delNode.next;
            delNode.next=null;
        }size--;
        return delNode.data;
    }

    public String toString(){
        StringBuffer sb=new StringBuffer(header.data);
        Node current=header;
        while(current.next!=header){
            sb.append(","+current.next.data.toString());
            current=current.next;
        }
        return sb.toString();

    }

    public static void main(String[] args) {
        CircularLinkedList c=new CircularLinkedList("0");
        c.addAtTail("A");
        c.addAtTail("B");
        c.addAtTail("C");
        System.out.println(c.getData(3));
        System.out.println(c.toString());
        System.out.println(c.size);
        System.out.println(c.delNodeByIndex(1));
        System.out.println(c.toString());
        System.out.println(c.size);
    }
}