_05_longestPalindrom.java

public class _05_longestPalindrom {

    static String longgestPalindrom(String s){
        if (s == null || s.length() < 1) {
            return "";
        }
        int start = 0, end = 0;
        for(int i = 0; i<s.length(); i++){
            int len1 = expandFromCenter(s, i, i);
            int len2 = expandFromCenter(s, i, i+1);
            int len = Math.max(len1, len2);
            if (len > (end - start)) {
                start = i - (len -1) /2;
                end = i + len / 2;
            }
        }
        
        return s.substring(start,end+1);
    }

    private static int expandFromCenter(String s, int left,int right){
        while (left >= 0 && right < s.length() && s.charAt(left) == s.charAt(right)) {
           left--;
           right++; 
        }
        return right - left - 1;
    }

    public static void main(String[] args) {
        String name = "abjahajbs";
        String val = longgestPalindrom(name);
        System.out.println(val);
    }
}