使用JAVA实现寻找一个字符串中最长的对称字符串:

如输入字符"121a123321",返回"123321". 　　实现代码:

 1 import org.junit.Test;
 2 
 3 public class MirroString {
 4     public  String getMaxMirroString(String s){//找出字符串中最长的对称字符串的方法
 5 
 6         if (s!=null||s.length() != 0) {
 7             int length = s.length();
 8             
 9             for (int strLength = length; strLength>1; strLength--){//控制检验对称字符串的长度
10                 int rightIndex = strLength-1;//作为右索引
11                 
12                 for(int leftIndex = 0; leftIndex <= s.length() - strLength; leftIndex++,rightIndex++){//左右索引右移
13                     int couple = s.substring(leftIndex,rightIndex+1).length()/2;//字符串整除2的值
14                     int count = 0;//数字符串中对称字符的对数
15                     
16                     for(int l = leftIndex,r = rightIndex; l<r; l++,r--) {//从外向内检索字符串左右字符
17                             if (s.charAt(l) == s.charAt(r)) {
18                                 count++;//字符串中对称的字符对数
19                             }
20                         }
21                     
22                     if (count == couple){//判断字符串是否完全对称
23                         return s.substring(leftIndex,rightIndex+1);
24                     }
25                 }
26             }
27             return "无对称字符";
28         }else return "字符串为空";
29     }
30 
31     @Test
32     public void Test(){//验证
33         MirroString mS = new MirroString();
34         System.out.println( mS.getMaxMirroString("abadefgfe"));
35         System.out.println(mS.getMaxMirroString("11221454"));
36         System.out.println(mS.getMaxMirroString("21221"));
37     }
38 
39 }

某次笔试题中迟迟无法做出,现在终于稀里糊涂做出来.希望有大神给出好的解法.