java--验证码（娱乐）

import java.util.Objects;
import java.util.Random;
import java.util.Scanner;
public class yanzhenma {
    public static void main(String[] args) {
        while(true){
            String mima=ma();
            System.out.println(mima);
            Scanner sc=new Scanner(System.in);
            String n=sc.nextLine();
            if(!Objects.equals(n,mima)){System.out.println("验证码错误");
            }
            else{
                System.out.println(n);
                System.out.println("验证码正确");
                break;
            }
        }
    }
//生成四位数验证码
    public static String ma(){
        char[]chs=new char[62];
        for(int i=0;i<chs.length;i++){
            if(i<26) chs[i] = (char) (i + 'a');
            else if(i<52) chs[i] = (char) (i + 'A'-26);
            else  chs[i] = (char) (i + '0'-52);
        }
        String result="";
        Random rand=new Random();
        for(int i=0;i<4;i++){
            int a=rand.nextInt(62);
            result+=chs[a];
        }
        return result;
    }
}