[LintCode] Count and Say

public String countAndSay(int n) {
        // Write your code here
        String s = "1";
        for(int i = 1; i < n; i++) {
            StringBuffer sb = new StringBuffer();
            int count = 1;
            for(int j = 1; j < s.length(); j++) {
                if(s.charAt(j) == s.charAt(j-1))
                    count++;
                else{
                    sb.append(count);
                    sb.append(s.charAt(j-1));
                    count = 1;
                }
            }
            sb.append(count);
            sb.append(s.charAt(s.length()-1));
            s = sb.toString();
        }
        return s;
    }