随机生成4位验证码，输入验证码与生成的比较，最多输入5次

package com.hanqi.lianxi;

import java.util.Random;
import java.util.Scanner;

public class yanzhengma
{

 public static void main(String[] args)
 {
         String str ="0123456789abcdefghigklmnopqrstuvwxyzABCDEFGHIGKLMNOPQRSTUVWXYZ";
         char[] array = new char[4];
         Random suiji = new Random();
         System.out.print("验证码为：");
         for(int i =0; i<4; i++)
         {          
          array[i]=str.charAt(suiji.nextInt(61));         
         }
         System.out.println(array);
         Scanner sr = new Scanner(System.in);
         System.out.println("请输入验证码：");     
    String aaa=new String(array);//把数组类型转换成字符串类型
    for(int j=0;j<5;j++)
    {
            if(sr.nextLine().equals(aaa))
            {
             System.out.println("输入正确");
             break;
            }
            else
            {
             if(j<=3)
                 {
              System.out.println("输入错误，请重新输入");
              System.out.print("验证码为：");
                    for(int i =0; i<4; i++)
                    {          
                     array[i]=str.charAt(suiji.nextInt(61));         
                    }
                    System.out.println(array);
                     aaa=new String(array);
              }
             else
             {System.out.println("输入错误，对不起，您已经没有了输入机会");}
            }
    }
 }

}