用户注册----自添加异常显示

public class UerService {

    public static void register (String username, String password) throws IllegalNameException {

        if(username == null || username.length() < 4 ||username.length() >11 ){
            //System.out.println("用户名不合法,长度必需在[4~11]之间");
            //return;
            throw new IllegalNameException("用户名不合法，长度必须在[4~11]之间");
        }
        //执行到此处，说明没有产生异常
        System.out.println("注册成功，欢迎["+username+"]");
    }
}


//创建一个自定义异常类IllegalNameException
public class IllegalNameException extends Exception{
    public IllegalNameException(){
    }

    public IllegalNameException(String s){
        super(s);
    }
}



public class Test {
    public static void main(String[] args) {
        UerService uerService = new UerService();
        try {
            uerService.register("hhh","321");
        } catch (IllegalNameException e) {
            e.printStackTrace();
            System.out.println(e.getMessage());
        }
    }
}