Java 模拟用户注册 自定义异常处理

import java.util.Scanner;
public class Test {
    
    
    public static void main(String[] args) {
    
    
        System.out.println("请输入用户名");
        Scanner scanner = new Scanner(System.in);
        String userName= scanner.next();
        System.out.println("请输入密码");
        String password=scanner.next();
        UserService userService = new UserService();
        try {
    
    
            userService.userRegister(null,password);
        } catch (RegisterException e) {
    
    
            System.out.printf(e.getMessage());//这里一定别忘了输出
        }
    }
}

public class RegisterException extends Exception{
    
    
    public RegisterException() {
    
    
    }

    public RegisterException(String message) {
    
    
        super(message);
    }
}//自己写异常就三步
//继承异常类
//写无参构造函数
//写有参构造函数
//完毕，就这么简单。

public class UserService {
    
    
    public void userRegister(String userName,String password) throws RegisterException {
    
    
        if(null==userName||userName.length()<6){
    
    
//            RegisterException registerException= new RegisterException("用户名过短");
//            throw registerException;
            throw  new RegisterException("用户名过短");
        }
        if(userName.length()>14){
    
    
            RegisterException registerException = new RegisterException("用户名过长");
            throw registerException;
        }
        System.out.println("输出注册成功，欢迎"+userName+"的到来");
    }
}