JAVA工具类 ==＞ 自定义随机获取N个字母或数字(0~9 a~z A~Z)

JAVA工具类 ==> 自定义随机获取N个字母或数字(0~9 a~z A~Z)

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1.采用"暴力法"

public static void main(String[] args){
        String str = "qwertyuiopasdfghjklzxcvbnm0123456789ZXCVBNMASDFGHJKLPOIUYTREWQ";
        Scanner sc = new Scanner(System.in);
        System.out.println("你想取几位随机数 : ");
        int a = sc.nextInt();
        String s = "";
        char[] arr = new char[a];
        Random random = new Random();
        for (int i = 0; i < a; i++) {
            int b = random.nextInt(str.length());
            arr[i] = str.charAt(b);
        }
        for (int i = 0; i < arr.length; i++) {
            s += arr[i];
        }
        System.out.println(s);

  }

2.数字字母分类讨论,char数组 ASCII码法

 public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        System.out.println("随机几位数的验证码 : ");