双链表的简介：
每个节点有数据data域（保存数据），next域（指向下一个节点），pre域（指向上一个节点）双链表因为有next，pre，所以可以自我删除单链表与双链表的比较：
单向链表，查找的方向只能是一个方向，而双向链表可以向前或者向后查找单向链表不能自我删除，需要靠辅助节点 ，而双向链表，则可以自我删除，所以前面我们单链表删除用Java代码实现双链表的增删改查：代码如下
代码实现： package com.sai.linkedList; /** * @Author sai * @Description 双向链表的增删改查 * @Time 2020-07-03 11:16 */ public class DoubleLinkedList_CRUD { public HeadNode_Double head = new HeadNode_Double(0,"",""); //头节点 public HeadNode_Double getHead() { //获取头节点 return head; } /** * 添加_有序 * @param headNode_double */ public void add2(HeadNode_Double headNode_double){ HeadNode_Double temp = head; //创建辅助指针 Boolean falg1 = false; //表示是否编号已经存在 Boolean falg2 = false; //表示是否到达尾部 while (true){ if(temp.next != null && temp.next.no == headNode_double.no){ //有相同的编号了 falg1 = true; break; } if(temp.next == null){ //到达尾部 falg2 = true; break; } if(temp.next.no > headNode_double.no){ //遍历找到编号比这个大的位置 (找到要插入的位置) break; } temp = temp.next; //指针后移 } if(falg1){ System.out.println("已经有相同编号的对象了，无法添加了！"); } else if (falg2){ //在尾部插入 headNode_double.pre = temp; temp.next = headNode_double; } else{ //在头部或者中间插入 headNode_double.next = temp.next; temp.next.pre = headNode_double; temp.next = headNode_double; headNode_double.pre = temp; } } /** * 添加_无序 * @param headNode_double */ public void add(HeadNode_Double headNode_double){ HeadNode_Double temp = head; //创建辅助指针 while (true){ if(temp.next == null){ //遍历找到尾部 break; } temp = temp.next; //指针后移 } temp.next = headNode_double; //构建连接下一个的指针 headNode_double.pre = temp; //构建连接上一个的指针 } /** * 查询 * @param head */ public void find(HeadNode_Double head){ if(head.next == null){ //判断链表是否为空 System.out.println("该链表为空！"); return; } HeadNode_Double temp = head.next; while (temp != null){ System.out.println(temp); temp = temp.next; } } /** * 修改 * @param newHead 链表头 * @param no 要修改的节点的编号 */ public void update(HeadNode_Double newHead,int no){ if(head.next == null){ //判断是否为空 System.out.println("此链表为空！"); return; } HeadNode_Double temp = head; //获取辅助指针 Boolean falg = false; //标识是否找到要修改的节点 while (true){ if(temp.next == null){ //到达尾部，跳出循环 break; } if(temp.next.no == no){ //找到要修改的节点 falg = true; break; } temp = temp.next; } if(falg){ temp.next.name = newHead.name; temp.next.nackName = newHead.nackName; System.out.println("修改成功！"); } else { System.out.println("未找到要修改的节点！"); } } /** * 删除 * @param head 要删除的节点的头部 * @param no 要删除的节点的编号 */ public void delete(HeadNode_Double head,int no){ if(head.next == null){ //判断是否为空 System.out.println("该链表为空！"); return; } HeadNode_Double temp = head.next; //获取辅助指针 Boolean falg = false; //标识是否找到要删除的节点 while (true){ if(temp == null){ //到达尾部，跳出循环 break; } if(temp.no == no){ //找到要删除的节点 falg = true; break; } temp = temp.next; //指针后移 } if(falg){ if(temp.next != null){ //判断是否是最后一个节点 temp.pre.next = temp.next; temp.next.pre = temp.pre; } temp.pre.next = null; System.out.println("删除成功！"); } else { System.out.println("没有找到要删除的节点！"); } } /** * 设置一个实体类 */ static class HeadNode_Double { private int no; //编号 private String name; //姓名 private String nackName; //诨名 private HeadNode_Double next; //指针 指向下一个节点（next域） private HeadNode_Double pre; //指针 指向上一个节点（pre域） //构造方法 public HeadNode_Double(int no, String name, String nackName) { this.no = no; this.name = name; this.nackName = nackName; } @Override public String toString() { return "HeadNode{" + "no=" + no + ", name='" + name + '\'' + ", nackName='" + nackName + '\'' + '}'; } } } 测试类： package com.sai.linkedList; /** * @Author sai * @Description 双向链表的增删改查的测试类 * @Time 2020-07-03 13:58 */ public class DoubleLinkedList_CRUD_TEst { public static void main(String[] args) { //实例化几个对象 DoubleLinkedList_CRUD.HeadNode_Double headNode_double1 = new DoubleLinkedList_CRUD.HeadNode_Double(1,"宋江","及时雨"); DoubleLinkedList_CRUD.HeadNode_Double headNode_double2 = new DoubleLinkedList_CRUD.HeadNode_Double(2,"卢俊义","玉麒麟"); DoubleLinkedList_CRUD.HeadNode_Double headNode_double3 = new DoubleLinkedList_CRUD.HeadNode_Double(3,"吴用","智多星"); DoubleLinkedList_CRUD.HeadNode_Double headNode_double4 = new DoubleLinkedList_CRUD.HeadNode_Double(4,"公孙胜","入云龙"); DoubleLinkedList_CRUD doubleLinkedList_crud = new DoubleLinkedList_CRUD(); //添加_无序 /*doubleLinkedList_crud.add(headNode_double1); doubleLinkedList_crud.add(headNode_double2); doubleLinkedList_crud.add(headNode_double3); doubleLinkedList_crud.add(headNode_double4);*/ //添加_有序 doubleLinkedList_crud.add2(headNode_double1); doubleLinkedList_crud.add2(headNode_double4); doubleLinkedList_crud.add2(headNode_double3); doubleLinkedList_crud.add2(headNode_double2); //查询 //doubleLinkedList_crud.find(doubleLinkedList_crud.getHead()); //System.out.println(); //修改 //DoubleLinkedList_CRUD.HeadNode_Double headNode_double = new DoubleLinkedList_CRUD.HeadNode_Double(3,"小吴","星星"); //doubleLinkedList_crud.update(headNode_double,3); //查询 //doubleLinkedList_crud.find(doubleLinkedList_crud.getHead()); //System.out.println(); //删除 //doubleLinkedList_crud.delete(doubleLinkedList_crud.getHead(),4); //查询 doubleLinkedList_crud.find(doubleLinkedList_crud.getHead()); } }