Java 用双向循环链表实现 遍历

package day2;

/**
 * 构建双向循环链表，实现遍历功能
 */
public class DoubleLB {

    public static void main(String[] args) {
        DoubleLB doubleLB = new DoubleLB();
        doubleLB.creatCicle(100);
        doubleLB.doubbl(30);
    }
    //头结点
    Entry head;
    void creatCicle(int length){
        for(int i= 1; i<=length;i++){
            Entry newEntry = new Entry(i*2);
            //初始化头结点，把next和pre都指向自己
            if(i==1){
                 head = new Entry(null,null,1);
                 head.next = head;
                 head.pre = head;
            }else{
                /**
                 * 1 ：新增节点newEntry 的next指向 头结点 head
                 * 2： newEntry的pre 指向 head的pre。这里头结点的pre可以看做 最后一个节点（便于理解），也就是要插入新节点的位置 前一个节点
                 * 3： 插入新节点的位置 前一个节点 的next指向 newEntry
                 * 4：头结点的pre 指向newEntry。
                 */
                newEntry.next =head;
                newEntry.pre = head.pre;
                //head.pre.next = newEntry;//new.pre.next =newEntry
                newEntry.pre.next = newEntry;
                head.pre = newEntry;

            }
        }
    }

    /**
     * 这里查看链表上的节点的字段number 是否有等于 输入的number。用到了双向遍历
     * @param number
     */
    void doubbl(int number){
        Entry nextNode = head.next;
        Entry preNode = head.pre;

         while(nextNode != preNode){
             System.out.println("next"+nextNode.getNumber()+": pre"+preNode.getNumber());
                if(nextNode.getNumber() == number || preNode.getNumber() ==number){
                    System.out.println(" find next"+nextNode.getNumber()+": pre"+preNode.getNumber());
                    return;
                }
                nextNode=nextNode.next;
                preNode=preNode.pre;
         }
    }

    class Entry{
        Entry next;
        Entry pre;
        int number;

        public Entry getNext() {
            return next;
        }

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

        public Entry getPre() {
            return pre;
        }

        public void setPre(Entry pre) {
            this.pre = pre;
        }

        public int getNumber() {
            return number;
        }

        public void setNumber(int number) {
            this.number = number;
        }

        public Entry(int number) {
            this.number = number;
        }

        public Entry(Entry next, Entry pre, int number) {
            this.next = next;
            this.pre = pre;
            this.number = number;
        }
    }

}