How to validate email address with regular expression

How to validate email address with regular expression

Email Regular Expression Pattern

^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*
      @[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$;

Description

^   #start of the line
  [_A-Za-z0-9-\\+]+ #  must start with string in the bracket [ ], must contains one or more (+)
  (   #   start of group #1
    \\.[_A-Za-z0-9-]+ #     follow by a dot "." and string in the bracket [ ], must contains one or more (+)
  )*   #   end of group #1, this group is optional (*)
    @   #     must contains a "@" symbol
     [A-Za-z0-9-]+      #       follow by string in the bracket [ ], must contains one or more (+)
      (   #         start of group #2 - first level TLD checking
       \\.[A-Za-z0-9]+  #           follow by a dot "." and string in the bracket [ ], must contains one or more (+)
      )*  #         end of group #2, this group is optional (*)
      (   #         start of group #3 - second level TLD checking
       \\.[A-Za-z]{2,}  #           follow by a dot "." and string in the bracket [ ], with minimum length of 2
      )   #         end of group #3
$   #end of the line

The combination means, email address must start with “_A-Za-z0-9-\\+” , optional follow by “.[_A-Za-z0-9-]“, and end with a “@” symbol. The email’s domain name must start with “A-Za-z0-9-“, follow by first level Tld (.com, .net) “.[A-Za-z0-9]” and optional follow by a second level Tld (.com.au, .com.my) “\\.[A-Za-z]{2,}”, where second level Tld must start with a dot “.” and length must equal or more than 2 characters.
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