一、单链表的实现

                无头单向非循环链表

定义异常用于判断所给位置是否合法

public class IndexNotLegal extends RuntimeException{public IndexNotLegal(){}public IndexNotLegal(String smg){super(smg);}
}

class ListNode中包含当前节点的值和下一个节点指向 

实现链表的头插，尾插，任意位置插入，查找，删除一个节点，打印，计数，清空 

import java.util.List;public class MySingleList {//节点class ListNode{public int val;public ListNode next;public ListNode(int val){this.val = val;next = null;}}public ListNode head;//代表链表的头结点//打印public void display(){ListNode cur = head;while(cur!=null){System.out.print(cur.val+"->");cur = cur.next;}System.out.println();}//节点个数public int size(){int count = 0;ListNode cur = head;while(cur!=null){count++;cur = cur.next;}return count;}//头插public void addFirst(int data){ListNode node = new ListNode(data);node.next = head;head = node;}//尾插法public void addLast(int data){ListNode node = new ListNode(data);if(head==null){head = node;return;}ListNode tail = head;while(tail.next != null){tail=tail.next;}tail.next = node;}//任意位置插入,第一个数据节点为0号下标public void addIndex(int index,int data){//判断合不合法try {checkIndex(index);}catch(IndexNotLegal e){e.printStackTrace();}if(index==0){addFirst(data);return;}if(index == size()){addLast(data);return;}ListNode cur = findIndexSubOne(index);ListNode node = new ListNode(data);node.next = cur.next;cur.next = node;}private void checkIndex(int index) throws IndexNotLegal{if(index<0||index>size()){throw new IndexNotLegal("index不合法");}}public ListNode findIndexSubOne(int index){ListNode cur = head;int count =0;while(count!=index-1){cur = cur.next;count++;}return cur;}//查找是否包含关键字key是否在单链表当中public boolean contains(int key){ListNode cur = head;while(cur!=null){if(cur.val==key){return true;}cur = cur.next;}return false;}//删除出现关键字为key的节点public void remove(int key){if(head==null){return;}ListNode del = head;ListNode pre = head;while(del!=null){if(del.val==key){pre.next = del.next;del = del.next;}else{pre = del;del = del.next;}}if(head.val==key){head = head.next;return;}//最后判断头结点}public void clear(){ListNode cur = head;while(cur!=null){ListNode curN = cur.next;cur.next = null;cur = curN;}head = null;}
}

二、LinkedList

1、介绍

LinkedList的底层是双向链表结构，由于链表没有将元素存储在连续的空间中，元素存储在单独的节点中，然后通过引用将节点连接起来了，因此在任意位置插入或者删除元素时，不需要搬移元素，效率比较高。

        LinkedList实现了List接口

        LinkedList的底层使用了双向链表

        LinkedList没有实现RandomAccess接口，因此LinkedList不支持随机访问

        LinkedList的任意位置插入和删除元素时效率比较高，时间复杂度为O(1)

        LinkedList比较适合任意位置插入的场景

2、方法介绍

        add

直接增加

插入到指定位置

 addAll：尾插c 中的所有元素

         remove

删除 index 位置元素

删除遇到的第一个 o

 get：获取下标 index 位置元素

set：将下标 index 位置元素设置为 element

clear：清空

contains：判断 o 是否在线性表中

indexOf：返回第一个 o 所在下标

lastIndexOf：返回最后一个 o 的下标

subList：截取部分 list

三、LinkedList遍历方法

public static void main1(String[] args) {LinkedList<Integer> list = new LinkedList<>();list.add(1);list.add(2);list.add(1,3);System.out.println(list);//直接打印System.out.println("==============");//foreach遍历for(Integer x: list){System.out.print(x+" ");}System.out.println();System.out.println("============");//for遍历int size = list.size();for (int i = 0; i < size; i++) {System.out.print(list.get(i)+" ");}System.out.println();System.out.println("============");//使用迭代器遍历-正向遍历Iterator<Integer> it = list.iterator();while(it.hasNext()){System.out.print(it.next()+" ");}System.out.println();System.out.println("============");Iterator<Integer> it2 = list.listIterator();while(it2.hasNext()){System.out.print(it2.next()+" ");}System.out.println();System.out.println("============");//使用迭代器遍历-反向遍历ListIterator<Integer> it3 = list.listIterator(list.size());while(it3.hasPrevious()){System.out.print(it3.previous()+" ");}System.out.println();System.out.println("============");}

 

 四、实现MyLikedList

        无头双向链表

定义异常用于判断所给位置是否合法

public class IndexNotIllegal extends RuntimeException{public IndexNotIllegal(){}public IndexNotIllegal(String smg){super(smg);}
}

方法实现 

public class MyLinkedList {static class ListNode{public int val;public ListNode prev;public ListNode next;public ListNode(int val){this.val = val;}}public ListNode head;//头结点public ListNode last;//尾节点public int size(){int size = 0;ListNode cur = head;while(cur!=null){size++;cur = cur.next;}return size;}public void display(){ListNode cur = head;while(cur!=null){System.out.print(cur.val+" ");cur = cur.next;}System.out.println();}public boolean contains(int key){ListNode cur = head;while(cur!=null){if(cur.val==key){return true;}cur = cur.next;}return false;}//头插法public void addFirst(int data){ListNode Node = new ListNode(data);if(head==null){head = last = Node;}else{Node.next = head;head.prev = Node;head = Node;}}//尾插法public void addLast(int data){ListNode Node = new ListNode(data);if(head==null){head = last = Node;}else{last.next = Node;Node.prev = last;last = Node;}}//任意位置插入,第一个数据节点为0号下标public void addIndex(int index,int data){try{checkIndex(index);}catch(RuntimeException e){e.printStackTrace();}if(index == 0){addFirst(data);return;}if(index == size()){addLast(data);return;}ListNode cur = findIndex(index);ListNode node = new ListNode(data);node.prev = cur.prev;node.next = cur;cur.prev.next = node;cur.prev = node;}private ListNode findIndex(int index){ListNode cur = head;while(index!=0){cur = cur.next;index--;}return cur;}public void checkIndex(int index)throws IndexNotIllegal{if(index<0||index>size()){throw new IndexNotIllegal("数组下标不合法");}}//删除第一次出现关键字为key的节点public void remove(int key){ListNode cur = head;while(cur!=null){if(cur.val==key) {if (cur == head) {//处理头节点head = head.next;if(head != null){head.prev = null;}else{last = null;}} else {if (cur.next == null) {//处理尾节点cur.prev.next = cur.next;last = last.prev;} else {cur.prev.next = cur.next;cur.next.prev = cur.prev;}}return;//删完一个就跳出}cur = cur.next;}}//删除所有值为key的节点public void removeAllKey(int key){ListNode cur = head;while(cur!=null){if(cur.val==key) {if (cur == head) {//处理头节点head = head.next;if(head != null){head.prev = null;}else{last = null;}} else {if (cur.next == null) {//处理尾节点cur.prev.next = cur.next;last = last.prev;} else {cur.prev.next = cur.next;cur.next.prev = cur.prev;}}}cur = cur.next;}}//得到单链表的长度public void clear(){ListNode cur = head;while(cur!=null){ListNode curN = cur.next;cur.next = null;cur.prev = null;cur = curN;}head = last = null;}}