Regular Expressions: check e-mail address

//https://baike.baidu.com/item/%E6%AD%A3%E5%88%99%E8%A1%A8%E8%BE%BE%E5%BC%8F/1700215?fr=aladdin 


public  class Mylearn_2 {
         public  static  void main (String [] args) { 
            
            CheckMail (); 
            
      
     } 
        
        public  static  void CheckMail () 
        { 
            
            // requirements: checking mail address 
            String = mail "[email protected]" ; 
            
            String REG = "[a-zA-Z0-9 _] + @ [a-zA-Z0-9] + (\\ [the Z-a-zA] +.) +"; // more accurate match 
            reg = "\\ @ \\ + W + W (W \\ \\ +.) + ";    // relatively inaccurate matching 
            
            
            
            
            System.out.println (mail.matches (REG)); 
         }

}