第一面第一个算法，最最愚蠢的方式写出啦了，

public class LongestNumString{

public static void main(String args[]){

String s = "dsd32fds4535435jk4354fd";

StringBuffer sb = new StringBuffer();

int max = 0;

int count;

String tmp="";

for(int i=0;i<s.length();i++){

count = 0;

while(Character.isDigit(s.charAt(i))){count++;sb.append(s.charAt(i));i++;};

if(count>max) {

max = count;

   tmp = sb.toString();

   sb.delete(0,sb.length());

   }

}

System.out.println(tmp);

}

}