java 双向链表 无法更新结点

Question

双向链表的增删改实现

问题：运行update02 方法时 为什么说找不到更新的结点呢

```java
package Linkedlist;

public class DoubleLinkedListDemo {
    //test area:
    public static void main(String[] args) {
        System.out.println("DLL test:");
        //create nodes
        HeroNode02OfDLL no1 = new HeroNode02OfDLL(1, "q", "q");
        HeroNode02OfDLL no2 = new HeroNode02OfDLL(2, "xx", "aaq");
        HeroNode02OfDLL no3 = new HeroNode02OfDLL(3, "zzq", "qzz");
        //create DLL
        DoubleLinkedList DLLForTest = new DoubleLinkedList();
        DLLForTest.add02(no1);
        DLLForTest.add02(no2);
        DLLForTest.add02(no3);

        DLLForTest.list02();

        //update method
        HeroNode02OfDLL newHeroNode = new HeroNode02OfDLL(2, "xxx", "xxx");
        DLLForTest.update02(newHeroNode);
        System.out.println("update version:");
        DLLForTest.list02();
        //delete method
        DLLForTest.delete02(3);
        System.out.println("deleted version:");
        DLLForTest.list02();
    }
}

class DoubleLinkedList {//create a DLL
    private HeroNode02OfDLL head = new HeroNode02OfDLL(0, "", "");

    public HeroNode02OfDLL getHead() {
        return head;
    }


    //1.go through method
    public void list02() {
        if (head.next == null) {
            System.out.println("the DLL is empty!");
            return;
        }
        HeroNode02OfDLL temp = head.next;
        while (true) {
            if (temp == null) {
                break;
            }
            System.out.println(temp);
            temp = temp.next;
        }
    }

    public void add02(HeroNode02OfDLL heroNode) { //2.add at the last
        HeroNode02OfDLL temp = head;
        while (true) {
            if (temp.next == null) {
                break;
            }
            temp = temp.next;
        }
        temp.next = heroNode;
        heroNode.pre = temp;
    }

    //3.update
    public void update02(HeroNode02OfDLL newHeroNode) {
        if (head.next == null) {
            System.out.println("the DLL is empty!");
            return;
        }
        HeroNode02OfDLL temp = head.next;
        boolean flag = false;//flag: weather find the node
        while (true) {
            if (temp == null) {//finished
                break;
            }
            temp = temp.next;
        }
        if (flag) {
            temp.name = newHeroNode.name;
            temp.nickname = newHeroNode.nickname;
        } else {
            System.out.println("can't find the node :" + newHeroNode + "and can't update");
        }
    }

    public void delete02(int no) {//4.delete method
        if (head.next == null) {
            System.out.println("DLL is empty!");
            return;
        }
        HeroNode02OfDLL temp = head;
        boolean flag = false;
        while (true) {
            if (temp.next == null) {//走到最后的最后
                break;
            }
            if (temp.no == no) ;//找到待删除节点，双向链表可以自我删除
            flag = true;
            temp = temp.next;
        }
        if (flag) {
            temp.pre.next = temp.next;
            if (temp.next != null) {
                temp.next.pre = temp.pre;//如果是最后一个节点就不用执行这一句，否则出现空指针
            }
        } else {
            System.out.printf("the node %d should be delete doesn't exist\n", no);
        }
    }
}

    class HeroNode02OfDLL {
        public int no;
        public String name;
        public String nickname;
        public HeroNode02OfDLL next;//default is null
        public HeroNode02OfDLL pre;//default is null

        public HeroNode02OfDLL(int no, String name, String nickname) {
            this.no = no;
            this.name = name;
            this.nickname = nickname;
        }

        @Override
        public String toString() {
            return "HeroNode [no = " + no + ",name =" + name + ", nickname =" + nickname + "]";
        }
    }

```