Title: defining a regular expression string, it determines whether the input is determined whether the e-mail address for the e-mail.

package cn.exercise;

import java.util.Scanner;

/**
 * @author WH
 * @project Java
 * @package cn.exercise
 * @date 2019/11/24 18:44
 */
public class Email {
    public static void main(String[] args) {
       
        Scanner e=new Scanner(System.in);

 String email="\\w*+[@]\\w+[.]\\w*";

String a = e.nextLine (); if (a.matches (email)) {System.out.println ( "mailbox");} else {System.out.println ( "not");}}}