做法與找出兩個字串的最長公共子串相似。先得到字串的反轉，再利用求最長公共子串的方法來求最長對稱子串。

	public static void fun1(String str1) {
		if(str1==null ||str1.length()==0) {
			return;
		}
		String str2 = verse(str1);
		fun2(str1, str2);
	}
	
	public static String verse(String str) {
		String string = "";
		if(str==null ||str.length()==0) {
			return string;
		}
		for(int i=str.length()-1; i>=0; i--) {
			string += str.charAt(i);
		}
		return string;
	}
	
	public static void fun2(String str1, String str2){
	    if(str1 == null || str2 == null || str1.length() == 0 || str2.length() == 0){
	      return;
	    }
	    int len1 = str1.length();
	    int len2 = str2.length();
	    String longest = "";
	    int length = 0;
	    for(int i=0; i<len1; i++){
	        int index1 = i;
	        for(int j=0; j<len2; j++){
	            String temp = "";
	            
	            if(str1.charAt(index1) == str2.charAt(j)){
	                temp += str1.charAt(index1);
	                int index2 = index1+1;
	                for(int k=j+1; k<len2; k++){
	                    if(index2<len1 && str1.charAt(index2) == str2.charAt(k)){
	                        temp += str1.charAt(index2);
	                        index2++;
	                    }else{
	                        break;
	                    }
	                }
	                if(temp.length() > length){
	                    length = temp.length();
	                    longest = temp;
	                }
	                
	            }
	        }
	    }
	    System.out.println(length);
	    System.out.println(longest);
	}
 

輸入："aabbbbcc"

輸出：4 bbbb