Main.java

package com.itranswarp.learnjava;

public class Main {

	public static void main(String[] args) {
		
		try {
			String token = login("admin1", "password");
			System.out.println("Token: " + token);
		} catch (LoginFailedException | UserNotFoundException e) {
			// TODO: handle exception
			e.printStackTrace();
		}
		
	}

	static String login(String username, String password){
		if (username.equals("admin")) {
			if (password.equals("password")) {
				return "xxxxxx";
			} else {
				// 抛出LoginFailedException:
				throw new LoginFailedException("Bad username or password.");
			}
		} else {
			// 抛出UserNotFoundException:
			throw new UserNotFoundException("User not found.");
		}
	}
	
	
}

BaseException.java

package com.itranswarp.learnjava;

public class BaseException extends RuntimeException {

	public BaseException() {
		super();
	}

	public BaseException(String message, Throwable cause) {
		super(message, cause);
	}

	public BaseException(String message) {
		super(message);
	}

	public BaseException(Throwable cause) {
		super(cause);
	}

}

class LoginFailedException extends BaseException{
	public LoginFailedException(String error_mess) {
		super(error_mess);
	}
}

class UserNotFoundException extends BaseException{
	public UserNotFoundException (String error_message) {
		super(error_message);
	}
}