验证码案例

package com.Test3;
import java.util.Random;
public class Test { 
    public static void main(String[] args) { 
        String dates="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        Random r=new Random();
        String code="";
        //产生一个五位的验证码
        for (int i = 0; i <5 ; i++) { 
            //随机产生一个索引
            int index = r.nextInt(dates.length());
            //根据索引获取字符
            char c = dates.charAt(index);
            //字符拼接
            code+=c;
        }
        System.out.println(code);
    }
}