Regular expression for validating email

provide the foundation for describing or matching data according to defined syntax rules.

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

The mapping sample given here exemplifies the power of Regular Expressions by identifying valid E-mail addresses.

In the given example, the input data can have E-mail addresses in multiple yet valid formats.

The learning curve for Regular expression may not be very easy for everyone.

Often this results in to underutilization of Regular Expression and true power is not harnessed.

List emails = new Array List(); emails.add("[email protected]"); emails.add("[email protected]"); emails.add("[email protected]"); emails.add("user? : false [email protected]: false Now lets modify the regex such that domain name must include at least one dot, and that the part of the domain name after the last dot can only consist of letters. The top-level domain (in these examples) must consist of two to six letters only.

[email protected]"); emails.add("user'[email protected]"); //Invalid emails emails.add("@yahoo.com"); String regex = "^[a-z A-Z0-9_! `~^.-] @[a-z A-Z0-9.-] $"; Pattern pattern = Pattern.compile(regex); for(String email : emails) Output: [email protected]: true [email protected] : true [email protected]: true user? List emails = new Array List(); emails.add("[email protected]"); emails.add("[email protected]"); emails.add("[email protected]"); emails.add("[email protected]"); emails.add("[email protected]"); //Invalid emails emails.add("[email protected]"); emails.add("[email protected]"); emails.add("[email protected]"); emails.add("[email protected]"); emails.add("[email protected]"); String regex = "^[\w!

)$"; Pattern pattern = Pattern.compile(regex); for(String email : emails) Output: [email protected]: true [email protected] : true [email protected]: true [email protected]: true [email protected] : true [email protected] : true [email protected] : true @: false This regex example uses all the characters permitted by RFC 5322, which governs the email message format. :[a-z A-Z0-9-] \.) [a-z A-Z]$"; Pattern pattern = Pattern.compile(regex); for(String email : emails) Output: [email protected]: true [email protected] : true [email protected]: true [email protected]: true [email protected]: true [email protected]: false [email protected] various use-cases, but especially at web-based registration forms we need to make sure the value we received is a valid e-mail address.Another common use-case is when we get a large text-file (a dump, or a log file) and we need to extract the list of e-mail address from that file.In my program I need to validate that tens of thousands of email addresses (which should be valid) are (within a reasonable doubt) valid email addresses.Using this code allows me to filter out the couple dozen (0.03%) that are invalid. Due to what I assume was a stray invisible character, I had a problem with the reg ex.

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Regular expressions are more powerful and flexible. You can search Numbers, punctuation characters, patterns and so on.

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  1. Her take: “I went out with a guy I met online who seemed really sweet and charming. A few days later, he texts me to say that he isn't looking for a girlfriend—just casual sex.