自定义异常练习，代码演示

测试类

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

/**
 * 步骤实现:
 *  1.自定义编译时异常:定义一个类继承Exception
 *  2.把构造方法生成
 *
 */
public class Demo01 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (true){
            System.out.println("请输入用户名:");
            String name = sc.next();
            System.out.println("请输入密码:");
            String password = sc.next();
            try {
                register(name,password);
                System.out.println("注册成功");
            } catch (RegisterException e) {
//                e.printStackTrace();

                System.out.println("注册出错了:"+e.getMessage());
            }
        }
    }

    public static boolean register(String name,String password) throws RegisterException {
        Map<String,String> accounts = new HashMap<>();
        accounts.put("Jack","123456");
        accounts.put("Rose","123456");
        //1.判断名字是否存在
        if(accounts.containsKey(name)){
            throw new RegisterException("账号已被注册,请更换!");
        }
        //2.密码是否合法6位
        if(password==null || password.length()!=6){
            throw new RegisterException("密码不规范");
        }

        accounts.put(name,password);

        System.out.println("accounts = " + accounts);
        return true;
    }
}

异常类

class RegisterException extends Exception{
    public RegisterException() {
    }

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

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

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

    public RegisterException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
        super(message, cause, enableSuppression, writableStackTrace);
    }
}