用户登录 自定义异常捕获

[java]代码库

FieldRequiredException.java
package Experience;

public class FieldRequiredException extends Exception{
	public FieldRequiredException(String who) {
		super(who+"不能为空！");
	}
}

WrongPasswordException.java
package Experience;

public class WrongPasswordException extends Exception{
	public WrongPasswordException() {
		super("密码错误！");
	}
}

UserNameNotFoundException.java
package Experience;

public class UserNameNotFoundException extends Exception{
	public UserNameNotFoundException() {
		super("用户名不存在！");
	}
}

LoginService.java
package Experience;

public class LoginService {
	
	public void login(String UserName,String password)
	throws FieldRequiredException,WrongPasswordException,
	UserNameNotFoundException{
		
		if (UserName==null||UserName.trim().length()<1) {
			throw new FieldRequiredException("用户名");
		}
		if (password==null||password.length()<1) {
			throw new FieldRequiredException("密码");
		}
		if (UserName.trim().equals("admin")) {
			if (password.equals("admin")) {
				return;
			}else {
				throw new WrongPasswordException();
			}
		}else {
			throw new UserNameNotFoundException();
		}
	}
	
}


LoginClient.java
package Experience;

import java.util.Scanner;

public class LoginClient {

	public static void main(String[] args) {
		
		try {
		
			Scanner scanner=new Scanner(System.in);
			System.out.println("请输入用户名：");
			String UserName=scanner.nextLine();
			System.out.println("请输入密码：");
			String password=scanner.nextLine();
			
			LoginService loginService=new LoginService();
			loginService.login(UserName, password);
			
		} catch (FieldRequiredException e) {
			
			System.err.println(e.getMessage());
			
		} catch (WrongPasswordException e) {
			
			System.err.println(e.getMessage());
			
		} catch (UserNameNotFoundException e) {
			
			System.err.println(e.getMessage());
		}
	}

}