public static int getSubCount_2(String str, String key) {
        int count = 0;
        int index = 0;
        while ((index = str.indexOf(key, index)) != -1) {
            index = index + key.length();

            count++;
        }
        return count;
    }

    public static void main(String[] args) {
        String str
 
 = "kkabkkcdkkefkks";
        //控制檯輸出4
        System.out.println(getSubCount_2(str, "kk"));
    }