随机验证码（案例）

//验证码
package com;

import java.util.Random;

public class World {

    public static void main(String[] args) {
        System.out.println(ma(5));
    }
    public static String ma(int n){
        Random random=new Random();
        String p="";
        for (int i = 0; i < n; i++) {

            int t = random.nextInt(3);//随机生成0-2

            switch (t){
                case 0:
                    char ch=(char)random.nextInt(65,90);//大写字母
                    p+=ch;
                    break;
                case 1:
                    char c=(char)random.nextInt(97,122);//小写字母
                    p+=c;
                    break;
                case 2:
                    p+=random.nextInt(10);//数字
                    break;
            }

        }
            return p;
            }
         }