Thousand Separator

给一个数字n, 返回加千位点号的n的字符串.

class Solution {
    public String thousandSeparator(int n) {
        StringBuilder sb = new StringBuilder();
        StringBuilder t = new StringBuilder(n+"");
        String s = t.reverse().toString();
        for(int i = 0 ; i < s.length(); i++) {
            if(i != 0 && i % 3 == 0)
                sb.append(".");
            sb.append(s.charAt(i));
        }
        return sb.reverse().toString();
    }
}