Java语言中的对象引用实际上是一个指针（这里的指针均为概念上的意义，而非语言提供的数据类型），所以我们可以编写这样的类来实现链表中的结点。
private static class Entry<E> {
E element // 当前存储元素
Entry<E> next // 下一个元素节点
Entry<E> previous // 上一个元素节点
Entry(E element, Entry<E> next, Entry<E> previous) {
this.element = element
this.next = next
this.previous = previous
}
}
将数据域定义成Object类是因为Object类是广义超类，任何类对象都可以给其赋值，增加了代码的通用性。为了使链表可以被访问还需要定义一个表头，表头必须包含指向第一个结点的指针和指向当前结点的指针。为了便于在链表尾部增加结点，还可以增加一指向链表尾部的指针，另外还可以用一个域来表示链表的大小，当调用者想得到链表的大小时，不必遍历整个链表。
链表的数据结构我们可以用类List来实现链表结构，用变量Head、Tail、Length、Pointer来实现表头。
存储当前结点的指针时有一定的技巧，Pointer并非存储指向当前结点的指针，而是存储指向它的前趋结点的指针,当其值为null时表示当前结点是第一个结点，因为当删除当前结点后仍需保证剩下的结点构成链表，如果Pointer指向当前结点，则会给操作带来很大困难。如何得到当前结点呢？我们定义了一个方法cursor(),返回值是指向当前结点的指针。类List还定义了一些方法来实现对链表的基本操作，通过运用这些基本操作我们可以对链表进行各种操作。
例如reset()方法使第一个结点成为当前结点。insert(Object d)方法在当前结点前插入一个结点，并使其成为当前结点。remove()方法删除当前结点同时返回其内容，并使其后继结点成为当前结点，如果删除的是最后一个结点，则第一个结点变为当前结点。
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}java中创建链表的例子：package zx
class Link{
private Node root
class Node{
private String name
private Node Next
public Node(String name){
this.name = name
}
public String getName(){
return this.name
}
public void addNode(Node newNode){
if(this.Next==null){
this.Next = newNode
}else{
this.Next.addNode(newNode)
}
}
public void printNode(){
System.out.print(this.name + "-->")
if(this.Next!=null){
this.Next.printNode()
}
}
}
public void add(String name){
Node newNode = new Node(name)
if(this.root==null){
this.root = newNode
}else{
this.root.addNode(newNode)
}
}
public void print(){
if(this.root!=null){
this.root.printNode()
}
}
}
public class LinkDemo {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Link link = new Link()
link.add("根节点")
link.add("第一节点")
link.add("第二节点")
link.add("第三节点")
link.add("第四节点")
link.print()
System.out.println("null")
}
}
