爪哇国新游记之十一----用异常控制流程

import java.util.HashMap;
import java.util.Map;


public class LoginService{
    private Map<String,String> map;
    
    public LoginService(){
        map=new HashMap<String,String>();
        
        map.put("张三", "123");
        map.put("李四", "123");
        map.put("王五", "123");
        map.put("赵六", "1234");
        map.put("孙七", "1234");
    }
    
    
    public boolean login(String name,String password) throws NoUserException,ErrorPswdException{
        
        if(map.containsKey(name)){
            String pswd=map.get(name);
            
            if(pswd.equals(password)==false){
                throw new ErrorPswdException("用户名"+name+"的密码不是"+password);
            }
        }else{
            throw new NoUserException("DB里没有这个用户名");
        }
        
        return true;
    }
    
    public static void main(String[] args){
        LoginService service=new LoginService();
        String name="张三1";
        String pswd="1235";
        
        try{
            boolean passed=service.login(name,pswd);
            
            System.out.println("欢迎"+name+"登录系统.");
        }catch(NullPointerException e){
            System.out.println("数据库未就绪，请通知系统管理员.");
        }catch(NoUserException e){
            System.out.println("用户名"+name+"不存在,即将前往注册页面");
        }catch(ErrorPswdException e){
            System.out.println("用户的"+name+"密码"+pswd+"不正确,请明确后再输入");
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}

public class ErrorPswdException extends Exception{
    public ErrorPswdException(String msg){
        super(msg);
    }
}

public class NoUserException extends Exception{
    public NoUserException(String msg){
        super(msg);
    }
}