Count and Say

public class Solution {    public String countAndSay(int n) {        if (n < 1) {            return "";        }        String res = "1";        for (int i = 0; i < n - 1; i++) {            StringBuilder sb = new StringBuilder();            int count = 1;            for (int j = 0; j < res.length(); j++) {                if (j + 1 < res.length() && res.charAt(j) == res.charAt(j + 1)) {                    count++;                } else {                    sb.append(count + "" + res.charAt(j));                    count = 1;                }            }            res = sb.toString();        }        return res;    }}