随机验证码

package com.Demo;

import java.util.Random;
//随机验证码
public class Test2 {
    public static void main(String[] args) {
        System.out.println(cali(5));

    }

    public static String cali(int n){
        Random r=new Random();
        String code="";
        for (int i = 1; i <=n ; i++) {
            int type=r.nextInt(3);
            switch (type){
                case 0:
                    code+=r.nextInt(10);
                    break;
                case 1:
                    char ch1= (char) (r.nextInt(26)+65);
                    code+=ch1;
                    break;
                case 2:
                    char ch2= (char) (r.nextInt(26)+97);
                    code+=ch2;
                    break;
            }
        }
        return code;
    }
}