java如何实现一个用户登陆程序，其中有三个类，主类、Check类、Operator类？

package cn.net.longin.demo.action;

import cn.net.longin.demo.entry.ResultJSON;
import cn.net.longin.demo.servcie.LoginService;

public class LoginMain {

public static void main(String[] args) {
    /**
     * 登录用户名
     */
   String username="admin";
    /**
     * 登录密码
     */
    String password="123456";
    //获取验证码
    String validate_code=LoginService.createVliadateCode(username);
    //登录
    ResultJSON result= login(username,validate_code);

}
private static ResultJSON login(String username,String code) {
    ResultJSON resultJson=new ResultJSON();
    if(LoginService.isExist(username)) {
        if(LoginService.validateCode(username, code)) {
            resultJson.setMessage("登录成功");
            resultJson.setStatus("success");
        }else {
            resultJson.setMessage("验证不通过");
            resultJson.setStatus("fail");
        }
    }else {
        resultJson.setMessage("用户不存在");
        resultJson.setStatus("fail");
    }
    return resultJson;
}

}
package cn.net.longin.demo.entry;

public class ResultJSON {
//返回状态
private String status;
//消息
private String message;
public String getStatus() {
return status;
}
public void setStatus(String status) {
this.status = status;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}

}
package cn.net.longin.demo.entry;

public class User {
private String username;
private String password;

public User(String username, String password) {
    super();
    this.username = username;
    this.password = password;
}
public String getUsername() {
    return username;
}
public void setUsername(String username) {
    this.username = username;
}
public String getPassword() {
    return password;
}
public void setPassword(String password) {
    this.password = password;
}

}
package cn.net.longin.demo.servcie;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.UUID;

import cn.net.longin.demo.entry.User;

public class LoginService {
private static Map user_validate_code=new HashMap();

private static List<User> user_info=new ArrayList<User>();
static {
    User user=new User("admin","123456");
    user_info.add(user);
}
/**
 * 创建验证码
 * @username 用户名
 * @return
 */
 public static String createVliadateCode(String username) {
     String code=UUID.randomUUID().toString();
     if(user_validate_code.containsKey(username)) {
         user_validate_code.remove(username);
     }
     user_validate_code.put(username, code);
     return  code;
 }
 /**
  * 判断是否存在
  * @param username
  * @return
  */
 public static boolean isExist(String username) {
     boolean flag=false;
     for(User user :user_info) {
         if(user.getUsername().equals(username)) {
             flag=true;
             break;
         }
     }
     return flag;
 }
 /**
  * 验证
  * @param username
  * @param code
  * @return
  */
 public static boolean validateCode(String username,String code) {
     boolean flag=false;
     if(user_validate_code.containsKey(username)) {
         if(user_validate_code.get(username).toString().equals(code)) {
             flag=true;
         }
     }
     return flag;
 }

}
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