3.循环链表

双向链表的增删改查功能

package com.zhiyang.linkedlist;

public class DoubleLinkedListDemo {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        HeroNode2 hero1 = new HeroNode2(1, "song", "及时雨");
        HeroNode2 hero2 = new HeroNode2(2, "卢俊义", "玉麒麟");
        HeroNode2 hero3 = new HeroNode2(3, "吴用", "智多星");
        HeroNode2 hero4 = new HeroNode2(4, "林冲", "豹子头");

        DoubleLinkedList doubleLinkedList = new DoubleLinkedList();
//      doubleLinkedList.addNode(hero1);
//      doubleLinkedList.addNode(hero2);
//      doubleLinkedList.addNode(hero3);
//      doubleLinkedList.addNode(hero4);

        doubleLinkedList.addByOrder(hero1);
        doubleLinkedList.addByOrder(hero4);
        doubleLinkedList.addByOrder(hero3);
        doubleLinkedList.addByOrder(hero2);
        doubleLinkedList.showList();

//      HeroNode2 newnode=new HeroNode2(4, "公孙胜", "入云龙");
//      doubleLinkedList.update(newnode);
//      doubleLinkedList.showList();
    }

}

class DoubleLinkedList {

    private HeroNode2 head = new HeroNode2(0, "", "");

    public HeroNode2 getHead() {
        return head;
    }

    // 链表遍历
    public void showList() {
        // 判断链表是否为空
        if (head.next == null) {
            return;
        }

        HeroNode2 tempHeroNode = head.next;
        while (true) {
            // 判断是否已经到达最后一个节点
            if (tempHeroNode == null) {
                break;
            }
            // 打印
            System.out.println(tempHeroNode);
            //
            tempHeroNode = tempHeroNode.next;

        }

    }

    public void addNode(HeroNode2 heronode) {
        HeroNode2 tempHeroNode = head;
        while (true) {
            // 获取最后的节点
            if (tempHeroNode.next == null) {
                break;
            }
            tempHeroNode = tempHeroNode.next;

        }
        // 将最后节点的next
        tempHeroNode.next = heronode;
        heronode.pre = tempHeroNode;

    }

    //
    // 根据编号添加节点
    public void addByOrder(HeroNode2 heronode) {
        HeroNode2 tmpHeroNode = head;
        boolean flag = false;
        while (true) {
            // 如果是最后一个节点，证明需要插入到最后，直接退出
            if (tmpHeroNode.next == null) {
                break;
            }
            // 找到插入位置
            if (tmpHeroNode.next.no > heronode.no) {
                break;
            } else if (tmpHeroNode.next.no == heronode.no) {
                flag = true;
                break;
            }
            tmpHeroNode = tmpHeroNode.next;

        }
        // 判断是否能够插入
        if (flag) {
            System.out.println("待插入节点已存在");

        } else {
            heronode.next = tmpHeroNode.next;
            tmpHeroNode.next = heronode;
            heronode.pre = tmpHeroNode;
        }

    }

    // 节点内容修改
    // 修改节点信息，编号不能变
    // 根据节点编号修改
    public void update(HeroNode2 newheroNode) {
        // 判断链表是否为空
        if (head.next == null) {
            System.out.println("链表为空");
            return;
        }
        HeroNode2 tmpHeroNode = head.next;
        boolean flag = false;
        while (true) {
            if (tmpHeroNode == null) {
                break;
            }
            if (tmpHeroNode.no == newheroNode.no) {
                flag = true;
                break;
            }
            tmpHeroNode = tmpHeroNode.next;
        }

        if (flag) {
            tmpHeroNode.name = newheroNode.name;
            tmpHeroNode.nickname = newheroNode.nickname;

        } else {
            System.out.printf("编号为%d的节点不存在\n", newheroNode.no);
        }

    }

    // 从双向链表中删除一个节点
    public void deletenode(int no) {
        if (head.next == null) {
            System.out.println("链表为空");
            return;
        }
        // 找到需要删除节点的前一个节点。
        HeroNode2 tmpHeroNode = head.next;
        boolean flag = false;
        while (true) {
            if (tmpHeroNode == null) {
                break;
            }

            if (tmpHeroNode.no == no) {
                flag = true;
                break;
            }
            tmpHeroNode = tmpHeroNode.next;

        }

        if (flag) {
            tmpHeroNode.pre.next = tmpHeroNode.next;
            // 如果是最后一个节点就不能执行下面这句，否则会执行空指针异常
            if (tmpHeroNode.next != null) {
                tmpHeroNode.next.pre = tmpHeroNode.pre;
            }

        } else {
            System.out.printf("编号为%d的节点不存在，无法删除\n", no);
        }

    }

}

class HeroNode2 {
    public int no;
    public String name;
    public String nickname;
    public HeroNode2 next;
    public HeroNode2 pre;

    public HeroNode2(int no, String name, String nickname) {
        super();
        this.no = no;
        this.name = name;
        this.nickname = nickname;
    }

    @Override
    public String toString() {
        return "HeroNode2 [no=" + no + ", name=" + name + ", nickname=" + nickname + "]";
    }

}