Validating last character regex

Email validation using regular expressions is common task which may be required in any application which seek email address as required information in registration step.There may be more usecase but that’s not point of discussion here. validating email address in java using regular expressions.List emails = new Array List(); emails.add("[email protected]"); emails.add("[email protected]"); emails.add("[email protected]"); emails.add("[email protected]"); emails.add("user#@in"); emails.add("[email protected]"); //Invalid emails emails.add("user#domain.com"); emails.add("@yahoo.com"); String regex = "^(. )$"; Pattern pattern = Pattern.compile(regex); for(String email : emails) Output: [email protected]: true [email protected] : true [email protected]: true [email protected]: true user#@in : true [email protected] : true user#: false @: false In this regex, we have added some restriction osn username part of email address.Restrictions in above regex are:1) A-Z characters allowed 2) a-z characters allowed 3) 0-9 numbers allowed 4) Additionally email may contain only dot(.), dash(-) and underscore(_) 5) Rest all characters are not allowed Let’s test some email addresses against above regex.^ #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. Almost every editor on every computer system can do this.Regular Expressions are more powerful and flexible. You can search numbers, punctuation characters, patterns and so on.

[email protected]– email’s first character can not start with dot “.” 7.

Here’s a Java example to show you how to use regex to validate email address. [email protected], [email protected], [email protected] [email protected], [email protected], [email protected] 3.

[email protected]%*– email’s tld is only allow character and digit 9. [email protected]– email’s last character can not end with dot “.” 11. [email protected] -email’s tld which has two characters can not contains digit Here’s a unit test using test NG.

A Regular Expression is nothing more than a pattern of characters itself, matched against a certain parcel of text.

Using Regular Expressions, it is simple to search for a specific word or string of characters.

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For example, matches nothing in "cndy", the 'a' in "candy," the first two a's in "caandy," and the first three a's in "caaaaaaandy" Notice that when matching "caaaaaaandy", the match is "aaa", even though the original string had more a's in it.

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