这个小程序使用面向对象方式实现起来很简单，就是在它在双向链表中循环直到剩下一个节点

public class ThreeToOne {
    public static void main(String[] args){
        LinkNode linkNode=new LinkNode();
        for(int i=0;i<6;i++){
            Node node=new Node(i);
            linkNode.add(node);
        }
        int count=0;
        System.out.println(linkNode.getNode().getObj());
    }
}

class Node{
    private Node prev;
    private Node next;
    private Object obj;

    public Node(Object obj){
        this.obj=obj;
    }

    public Node getPrev() {
        return prev;
    }

    public void setPrev(Node prev) {
        this.prev = prev;
    }

    public Node getNext() {
        return next;
    }

    public void setNext(Node next) {
        this.next = next;
    }

    public Object getObj() {
        return obj;
    }

    public void setObj(Object obj) {
        this.obj = obj;
    }
}

class LinkNode {
    private Node first;
    private Node last;

    public Node getFirst() {
        return first;
    }

    public void setFirst(Node first) {
        this.first = first;
    }

    public Node getLast() {
        return last;
    }

    public void setLast(Node last) {
        this.last = last;
    }

    public void add(Node node){
        if(first==null){
            first=last=node;
        }
        else {
            Node oldLast=last;
            last.setNext(node);
            node.setPrev(last);
            last=node;
            last.setNext(first);
            first.setPrev(last);
        }
    }

    public void del(Node node){
        if(node==first){
            Node newFirst=first.getNext();
            newFirst.setPrev(last);
            last.setNext(newFirst);
            first=newFirst;
        } else if (node==last) {
            Node newLast=last.getPrev();
            newLast.setNext(first);
            first.setPrev(newLast);
            last=newLast;
        } else {
            Node curr=first;
            while (curr!=node){
                curr=curr.getNext();
                if(curr==node) {
                    Node prev=curr.getPrev();
                    Node next=curr.getNext();
                    prev.setNext(next);
                    next.setPrev(prev);
                    break;
                }
            }
        }
    }

    public Node getNode(){
        int count=0;
        Node node=first;
        while (node!=null){
            if(first==last){
                break;
            }
            count++;
            if(count==3){
                count=0;
                del(node);
                System.out.println("del-->"+node.getObj());
            }
            node=node.getNext();
        }
        return node;
    }
}