public static void palindrome(String str) {

            int len = str.length(); 

            int max = 1;

            for(int i = 1; i < len; i++){

                int low = i-1;      //偶数情况 

                int high = i; 

                while(low >= 0 && high < len && str.charAt(low) == str.charAt(high)){ 

                    low--; 

                    high++; 

                } 

                if(high-low-1 > max){ 

                    max = high-low-1;

                }

                low = i-1;      //奇数情况 

                high = i+1; 

                while(low >= 0 && high < len && str.charAt(low) == str.charAt(high)){ 

                    low--; 

                    high++; 

                } 

                if(high-low-1 > max){ 

                    max = high-low-1;

                } 

            } 

            System.out.println(max); 

    } 

    public static void main(String[] args) {

        String s = "1234321123565321"; 

        palindrome(s);

    }