统计从1到N之间自然数中包含有多少个2？如1-20中，有2,12,20这三个自然数，有3个2

 public static void main(String[] args) {
        long start = System.currentTimeMillis();
        int sum1 = count(20);
        long end = System.currentTimeMillis();


        System.out.println("统计的数量：" + sum1);
        System.out.println("时间(毫秒)：" + (end - start));
    }

    public static int count(int n) {
        List<String> list = new ArrayList<>();
        if (n <= 0) {
            return 0;
        }
        int count = 0;
        for (int j = 2; j <= n; j++) {
            String str = j + "";
            for (int k = 0; k < str.length(); k++) {
                if ((str.charAt(k) + "").equals("2")) {
                    count++;
                    list.add(str);
                }
            }
        }26         return count;
    }