java单链表实现

package com.marthevin.linkedlist;

public class LinkedListTest {

public static void main(String[] args)
{
LinkList linklist = new LinkList();
linklist.addFirstNode(21);
System.out.println(linklist.findPosByData(2));
linklist.displayAllNodes();
}
}

class Node{
protected Node link;
protected int data;

public Node(int data)
{
this.data = data;
}
}

class LinkList{
public Node first,last;//标识首末节点
public int  pos = 1; //位置
protected int count; //节点个数
public LinkList()
{
first = null;
last = null;
count = 0;
}

//在链表开头加入节点 OK
public void addFirstNode(int data)
{
Node newnode = new Node(data);
newnode.link = null;
//刚开始空节点
if(first==null)
{
first = newnode;
last = newnode;
count ++;
}else  //多于一个节点
{
newnode.link = first;
first = newnode;
count++;
}
}
//删除首节点 OK
public boolean deleteFirstNode()
{

boolean flag = false;
if(count==0){//空链表
System.out.println("空链表 删除失败");
return flag;
}else if(count==1){ //只有一个节点

first = null;
last = null;
count--;
flag = true;

}else{  //count>=2
first = first.link;
count--;
flag = true;
}
return flag;
}

//在最后加入节点 OK
public boolean addLastNode(int data)
{
boolean flag = false;
Node newnode = new Node(data);
newnode.link = null;
if(count==0) //空链表
{
first = newnode;
last = newnode;
count++;
flag = true;
}else
{
last.link = newnode;
count++;
flag=true;
}
return flag;
}

//删除最后一个节点  OK
public boolean deleteLastNode()
{
boolean flag = false;
Node current=null,prior=null;
if(count==0)//空节点
{
System.out.println("空链表，删除失败！");
return flag;
}else if(count==1) //只有一个节点
{
first = null;
last = null;
count--;
flag = true;
}else{  //大于等于两个节点
current = first;
prior = first;
while(current.link!=null)
{
prior = current;
current = current.link;
}
last = prior;
prior.link = null;
count--;
flag = true;
}
return flag;
}

//在任意位置之后插入节点,index 从1开始 OK
public boolean add(int index,int data)
{
Node newnode = new Node(data);
newnode.link = null;
boolean flag = false;
if(index>count||index<1)
{
System.out.println("index err");
return flag;
}
if(first==null)//count = 0 index = 0
{
first = newnode;
last = newnode;
count++;
flag = true;
}else if(index==count) //插到末节点之后
{
last.link = newnode;
last = newnode;
count++;
flag = true;
}else{  //index 在头结点 和最后节点之间
Node current = first;
while(pos<index)
{
current = current.link;
pos++;
}
newnode.link = current.link;
current.link = newnode;
count++;
this.pos = 1; //将位置重新置为1
flag = true;
}

return flag;
}

//删除任意位置的节点 OK
public boolean deleteNodeByPos(int pos)
{
boolean flag = false;
Node current=null,prior=null;
if(pos<1||pos>count)
{
System.out.println("pos error!");
return flag;
}
if(count==1) //只有一个节点。且pos只能为1
{
first = null;
last = null;
count--;
flag = true;
}else if(count==pos) //删除尾节点
{
current = first;
prior = first;
while(current.link!=null)
{
prior = current;
current = current.link;
}
last = prior;
prior.link = null;
count--;
flag = true;
}else{ //大于1
current = first;
prior = first;
if(pos==1) //删除首节点
{
first = first.link;
count--;
this.pos = 1;
flag = true;
}else{
while(this.pos<pos)
{
prior = current;
current = current.link;
this.pos++;
}
prior.link = current.link;
count--;
this.pos = 1;
flag = true;
}
}
return flag;
}

//根据节点的data删除节点  OK
public boolean deleteNodeByData(int data)
{
boolean flag = false;
Node current = null,prior = null;
if(count==0)//空链表
{
System.out.println("空链表，删除失败！");
return flag;
}else {
current = first; prior = first;
while(current.data!=data&¤t.link!=null)
{
this.pos++;
prior = current;
current = current.link;
}
if(current.data==data&¤t.link!=null&&this.pos!=1)//大于一个节点 且找到 非首末节点
{
prior.link = current.link;
count--;
flag = true;
}else if(current.data==data&¤t.link==null&&count==1)//只有一个节点，且找到 删除第一个节点
{
first = null;
last = null;
count--;
flag = true;
}
else if(current.data==data&&this.pos==1&¤t.link!=null)//找到 为第一个节点
{
first = first.link;
count--;
flag = true;
}
else if(current.data==data&¤t.link==null)//找到 为最后一个节点
{
last = prior;
prior.link = null;
count--;
flag = true;
}else{ //未找到
System.out.println("未找到给节点！");
return flag;
}
}
this.pos = 1;
return flag;
}

//根据位置找节点
public int findDataByPos(int pos)
{
Node current = first;
if(pos<1||pos>count)
{
System.out.println("pos error!");
return 0;
}
while(this.pos<pos)
{
current = current.link;
this.pos++;
}
this.pos = 1;
return current.data;
}

//根据数据找位置 返回第一个 OK
public int findPosByData(int data)
{
Node current = first;
int dataPos = 0;
if(first==null)
{
System.out.println("空链表，无法查找！");
return 0;
}
while(current.data!=data&¤t.link!=null)
{
current = current.link;
this.pos++;
}
if(current.data==data) //找到数据 返回pos
{
dataPos = this.pos;
this.pos = 1;
return dataPos;
}else{  //未找到数据
System.out.println("链表中不存在该数据！");
this.pos = 1;
return 0;
}

}

//打印所有节点 OK
public void displayAllNodes()
{

if(first==null)
{
System.out.println("空链表！");
}else{
Node current = first;
while(current!=null)
{
System.out.println(current.data);
current = current.link;
}
}

}

}