给一个字符串切割为ip

import java.util.*;

public class Main {
    public static void main(String[] args) {
        String ipAdress = new String("19216801");
        char[] ip = ipAdress.toCharArray();
        dfs(ip,0,new String[4],0);
    }


    public static void dfs(char[] arr,int level,String[] str,int used){
        if(level>=4 || used==arr.length){
            if(level>=4 && used==arr.length) {
                System.out.println(Arrays.toString(str));
            }
            return;
        }
        for(int i=1;i<4;i++){                                                               //取i个数
            String temp = "";
            int len = used+i;
            if(len>arr.length){                                                         //防止越界
                len=arr.length;
            }
            for(int j=used;j<len;j++){                                                  //给存储结果赋值
               temp = temp+arr[j];
            }
            if(temp.length()>1 && temp.substring(0,1).equals("0")){                         //防止出现01这种现象
                continue;
            }
            str[level] = temp;
            if(Integer.valueOf(str[level])<=255&&Integer.valueOf(str[level])>=0){           //筛选
                dfs(arr,level+1,str,used+i);
            }
            str[level] = "";                                                              //复原
        }
    }
}