用node。

javaListNode链表就是用Java自定义实现的链表结构。

链表是一种物理存储单元上非连续、非顺序的存储结构，数据元素的逻辑顺序是通过链表中的指针链接次序实现的。链表由一系列结点组成，结点可以在运行时动态生成。

双向链表：就是有双向指针，即双向的链域。\x0d\x0a链结点的结构：\x0d\x0a┌────┬────┬────────┐\x0d\x0a│ data │ next │ previous │\x0d\x0a└────┴────┴────────┘\x0d\x0a双向链表不必是双端链表(持有对最后一个链结点的引用)，双端链表插入时是双向的。\x0d\x0a有两条链：一条从头到尾，一条从尾到头，删除遍历时也是双向的。\x0d\x0a/**\x0d\x0a * 双向链表\x0d\x0a */\x0d\x0apublic class DoublyLinkedList {\x0d\x0aprivate Link head //首结点\x0d\x0aprivate Link rear //尾部指针\x0d\x0apublic DoublyLinkedList() { }\x0d\x0apublic T peekHead() {\x0d\x0aif (head != null) {\x0d\x0areturn head.data\x0d\x0a}\x0d\x0areturn null\x0d\x0a}\x0d\x0apublic boolean isEmpty() {\x0d\x0areturn head == null\x0d\x0a}\x0d\x0apublic void insertFirst(T data) {// 插入 到 链头\x0d\x0aLink newLink = new Link(data)\x0d\x0aif (isEmpty()) {//为空时，第1次插入的新结点为尾结点\x0d\x0arear = newLink\x0d\x0a} else {\x0d\x0ahead.previous = newLink//旧头结点的上结点等于新结点\x0d\x0a}\x0d\x0anewLink.next = head//新结点的下结点旧头结点\x0d\x0ahead = newLink//赋值后，头结点的下结点是旧头结点，上结点null\x0d\x0a}\x0d\x0apublic void insertLast(T data) {//在链尾 插入\x0d\x0aLink newLink = new Link(data)\x0d\x0aif (isEmpty()) {\x0d\x0ahead = newLink\x0d\x0a} else {\x0d\x0arear.next = newLink\x0d\x0a}\x0d\x0anewLink.previous = rear\x0d\x0arear = newLink//赋值后，尾结点的上结点是旧尾结点，下结点null\x0d\x0a}\x0d\x0apublic T deleteHead() {//删除 链头\x0d\x0aif (isEmpty()) return null\x0d\x0aLink temp = head\x0d\x0ahead = head.next//变更首结点，为下一结点\x0d\x0aif (head != null) {\x0d\x0ahead.previous = null\x0d\x0a} else {\x0d\x0arear = null\x0d\x0a}\x0d\x0areturn temp.data\x0d\x0a}\x0d\x0apublic T deleteRear() {//删除 链尾\x0d\x0aif (isEmpty()) return null\x0d\x0aLink temp = rear\x0d\x0arear = rear.previous//变更尾结点，为上一结点\x0d\x0aif (rear != null) {\x0d\x0arear.next = null\x0d\x0a} else {\x0d\x0ahead = null\x0d\x0a}\x0d\x0areturn temp.data\x0d\x0a}\x0d\x0apublic T find(T t) {//从头到尾find\x0d\x0aif (isEmpty()) {\x0d\x0areturn null\x0d\x0a}\x0d\x0aLink find = head\x0d\x0awhile (find != null) {\x0d\x0aif (!find.data.equals(t)) {\x0d\x0afind = find.next\x0d\x0a} else {\x0d\x0abreak\x0d\x0a}\x0d\x0a}\x0d\x0aif (find == null) {\x0d\x0areturn null\x0d\x0a}\x0d\x0areturn find.data\x0d\x0a}\x0d\x0apublic T delete(T t) {\x0d\x0aif (isEmpty()) {\x0d\x0areturn null\x0d\x0a}\x0d\x0aLink current = head\x0d\x0awhile (!current.data.equals(t)) {\x0d\x0acurrent = current.next\x0d\x0aif (current == null) {\x0d\x0areturn null\x0d\x0a}\x0d\x0a}\x0d\x0aif (current == head) {\x0d\x0ahead = head.next\x0d\x0aif (head != null) {\x0d\x0ahead.previous = null\x0d\x0a}\x0d\x0a} else if (current == rear) {\x0d\x0arear = rear.previous\x0d\x0aif (rear != null) {\x0d\x0arear.next = null\x0d\x0a}\x0d\x0a} else {\x0d\x0a//中间的非两端的结点，要移除current\x0d\x0acurrent.next.previous = current.previous\x0d\x0acurrent.previous.next = current.next\x0d\x0a}\x0d\x0areturn current.data\x0d\x0a}\x0d\x0apublic boolean insertAfter(T key, T data) {//插入在key之后, key不存在return false\x0d\x0aif (isEmpty()) {\x0d\x0areturn false\x0d\x0a}\x0d\x0aLink current = head\x0d\x0awhile (!current.data.equals(key)) {\x0d\x0acurrent = current.next\x0d\x0aif (current == null) {\x0d\x0areturn false\x0d\x0a}\x0d\x0a}\x0d\x0aLink newLink = new Link(data)\x0d\x0aif (current == rear) {\x0d\x0arear = newLink\x0d\x0a} else {\x0d\x0anewLink.next = current.next\x0d\x0acurrent.next.previous = newLink\x0d\x0a}\x0d\x0acurrent.next = newLink\x0d\x0anewLink.previous = current\x0d\x0areturn true\x0d\x0a}\x0d\x0apublic void displayList4Head() {//从头开始遍历\x0d\x0aSystem.out.println("List (first-->last):")\x0d\x0aLink current = head\x0d\x0awhile (current != null) {\x0d\x0acurrent.displayLink()\x0d\x0acurrent = current.next\x0d\x0a}\x0d\x0a}\x0d\x0apublic void displayList4Rear() {//从尾开始遍历\x0d\x0aSystem.out.println("List (last-->first):")\x0d\x0aLink current = rear\x0d\x0awhile (current != null) {\x0d\x0acurrent.displayLink()\x0d\x0acurrent = current.previous\x0d\x0a}\x0d\x0a}\x0d\x0a\x0d\x0aclass Link {//链结点\x0d\x0aT data//数据域\x0d\x0aLink next//后继指针，结点 链域\x0d\x0aLink previous//前驱指针，结点 链域\x0d\x0aLink(T data) {\x0d\x0athis.data = data\x0d\x0a}\x0d\x0avoid displayLink() {\x0d\x0aSystem.out.println("the data is " + data.toString())\x0d\x0a}\x0d\x0a}\x0d\x0apublic static void main(String[] args) {\x0d\x0aDoublyLinkedList list = new DoublyLinkedList()\x0d\x0alist.insertLast(1)\x0d\x0alist.insertFirst(2)\x0d\x0alist.insertLast(3)\x0d\x0alist.insertFirst(4)\x0d\x0alist.insertLast(5)\x0d\x0alist.displayList4Head()\x0d\x0aInteger deleteHead = list.deleteHead()\x0d\x0aSystem.out.println("deleteHead:" + deleteHead)\x0d\x0alist.displayList4Head()\x0d\x0aInteger deleteRear = list.deleteRear()\x0d\x0aSystem.out.println("deleteRear:" + deleteRear)\x0d\x0alist.displayList4Rear()\x0d\x0aSystem.out.println("find:" + list.find(6))\x0d\x0aSystem.out.println("find:" + list.find(3))\x0d\x0aSystem.out.println("delete find:" + list.delete(6))\x0d\x0aSystem.out.println("delete find:" + list.delete(1))\x0d\x0alist.displayList4Head()\x0d\x0aSystem.out.println("----在指定key后插入----")\x0d\x0alist.insertAfter(2, 8)\x0d\x0alist.insertAfter(2, 9)\x0d\x0alist.insertAfter(9, 10)\x0d\x0alist.displayList4Head()\x0d\x0a}\x0d\x0a}

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