java 随机生成验证码 思路

通过ASCII表生成大小写验证码

 public static void main(String[] args) {

        System.out.println( createCode(6));
    }
    public static String createCode(int n){ //int n 表示随机生成几位
        Random r = new Random();
        String code = "";
        for (int i = 0; i < n; i++) {
            int type = r.nextInt(3);
            switch (type){
                case 0:  //大写字母 ASCII码
                  char ch = (char)(r.nextInt(25)+65);
                    code += ch;
                    break;
                case 1: //小写字母 ASCII码
                    char ch1 = (char)(r.nextInt(25)+97);
                    code += ch1;
                    break;
                case 2: //数字
                    code += r.nextInt(10);
                    break;
            }
        }
        return code ;
    }
}