Validating email in java

You can test your program and reassure that your regular expression meets the rules on your policy about the form of the email addresses.

This is a basic test class:package com.core; import static org.junit.

And i If you need to validate users email addresses, consider sending them a verification to confirm that what they have given you is correct, but if you really want to be strict about things – consider a pre-built validation package. A very simple regular expression to validate that an email address generally fits the form required – now email your user and make sure they receive it!

Unit testing is very important in these situations because they provide good feedback about the correctness of our regular expressions.

The fully compliant RFC-822 email regex is nothing to be trifled with; in fact, it is a behemoth.

As such, I recommend using only a simple regular expression for this task.

In the last post, I explained about java regular expression in detail with some examples.

*/ User Info u = new User Info (); // loop until you get valid one(s) while (! ^ #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] # 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. Email is valid : [email protected], true Email is valid : [email protected], true Email is valid : [email protected], true Email is valid : [email protected], true Email is valid : [email protected], true Email is valid : [email protected] , true Email is valid : [email protected], true Email is valid : [email protected] , true Email is valid : mkyong [email protected], true Email is valid : [email protected], true Email is valid : mkyong , false Email is valid : [email protected] , false Email is valid : [email protected] , false Email is valid : [email protected], false Email is valid : [email protected] , false Email is valid : [email protected], false Email is valid : mkyong()*@, false Email is valid : [email protected]%*, false Email is valid : [email protected], false Email is valid : [email protected], false Email is valid : [email protected]@, false Email is valid : [email protected] , false PASSED: Valid Email Test([ 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 (au, my) “\.[A-Za-z]”, where second level Tld must start with a dot “.” and length must equal or more than 2 characters. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.Email validation in backend is very important and tricky task.

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