Write a function to find the longest common common string amongst an array of strings.

这个算法我是求的公共子序列，而不是公共前缀。提交到公共前缀的online不会通过。

public class Solution {    public String longestCommonPrefix(String[] strs) {        // Note: The Solution object is instantiated only once and is reused by each test case.    if(strs==null||strs.length==0){    return "";    }    if(strs.length==1){    return strs[0];    }    String s=strs[0];    for (int i=1;i<strs.length;i++ ){    s=findTwo(s,strs[i]);        }        return s;    }        String findTwo(String s0,String s1){    if(s0==null||s1==null||s0==""||s1==""){    return "";    }    if(s0.charAt(0)==(s1.charAt(0))){    if (s0.length()==1||s1.length()==1){    return s0.substring(0,1);    }    return s0.charAt(0)+findTwo(s0.substring(1),s1.substring(1));    }    else {        if(s0.length()==1||s1.length()==1){    if(s0.length()==s1.length()){    return "";    }    else     return s0.length()>s1.length()? findTwo(s1,s0.substring(1)):findTwo(s0,s1.substring(1));    }    String ss0=findTwo(s0,s1.substring(1));    String ss1=findTwo(s0.substring(1),s1);        int temp0=(ss0=="")?0:ss0.length();    int temp1=(ss1=="")?0:ss1.length();        return temp0>temp1?ss0:ss1 ;    }    }    public  static void  main(String[] args){    Solution test=new Solution();    String[] strs={"afg","dafegee"};    System.out.println(test.longestCommonPrefix(strs));    }    }