Java regex for removing all characters except a pattern

Question

I have a string including e-mail. There are probably extra characters before and / or after it. input examples:

[email protected]
[email protected] abcd efg
x y z [email protected]
p q [email protected] x z
asd[[email protected]]gh

I want to remove the extra characters.

Desired outputs:

[email protected]
[email protected]
[email protected]
[email protected]
[email protected]

Valid characters are a-zA-Z0-9._ So there are probably invalid characters before and / or after e-mail.

I tried this code to identify whether it is a correct email or not (this assumes that it is separated from extra characters by space), but I can not replace to the desired string (using s.replaceAll()):

if (s.matches("(?i).*\\s[a-zA-Z_\\.]+@[a-zA-Z_\\.]+\\.[a-zA-Z_\\.]+.*") ||
    fields[2].matches("(?i).*[a-zA-Z_\\.]+@[a-zA-Z_\\.]+\\.[a-zA-Z_\\.]+\\s.*"))

Read [this](http://stackoverflow.com/questions/201323/using-a-regular-expression-to-validate-an-email-address) — Reimeus, Aug 28 '14 at 19:03
Don't use `matches` or `replaceAll`. Instead, set up a [`Matcher`](http://docs.oracle.com/javase/8/docs/api/java/util/regex/Matcher.html), use `find` (which will find a pattern anywhere in the string), and use `group(0)` to return the string it finds. It will be much easier to tell it to return the matched string than to tell it to remove the unmatched characters. — ajb, Aug 28 '14 at 19:04
Valid characters are `a-zA-Z0-9._` ... How does your regular expression match the `12345` in the email addresses in your desired output?? — hwnd, Aug 28 '14 at 19:08
You're probably best off using this regex: \S@\S Your regex will miss a ton a valid email addresses. There are a lot of valid characters allowed in an email address. — tobii, Aug 28 '14 at 19:21
My email address is `[email protected]`. That is a perfectly valid email address. Your regex will not allow it. — Qix - MONICA WAS MISTREATED, Aug 28 '14 at 19:28
@tobii, Qix: My question was not about the validating the characters. Since I have defined a set of valid characters, I wanted to extract the email mentioned in the approach of Nemo. — Alisa, Aug 28 '14 at 20:59

score 1 · Accepted Answer · answered Aug 28 '14 at 19:48

you can use java.util.regex.Pattern and java.util.regex.Matcher

This code will do what you ask for:

public static void main(String[] args) {
    String[] testList = {"[email protected]", 
            "[email protected] abcd efg", 
            "x y z [email protected]", 
            "p q [email protected] x z", 
            "asd[[email protected]]gh"};

    Pattern EMAIL_PATTERN = Pattern.compile("[_A-Za-z0-9-]+(\\.[_A-Za-z0-9-]+)*@[A-Za-z0-9-]+(\\.[A-Za-z0-9-]+)*(\\.[A-Za-z]{2,})");


    for(String test : testList){
        Matcher m = EMAIL_PATTERN.matcher(test);
        while (m.find()) {
             System.out.println(m.group(0));
        }
    }
}

score 0 · Answer 2 · answered Aug 28 '14 at 19:20

0

Given your definition of valid characters, try:

^.*?([\w.]+@[\w.]+).*$

and replace with capturing group 1

answered Aug 28 '14 at 19:20

Ron Rosenfeld

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score 0 · Answer 3 · answered Aug 28 '14 at 19:33

A validation of email addresses is not possible. It is only possible to validate an email-adress-like-appearence - and even this task is quite tricky, due to new tlds with more than 3 characters.

So, you better find "invalid" email-adresses (mail sending will fail), then missing a valid one.

Use

([a-zA-Z0-9!#$%&'*+-/=?^_`{|}~.]+\@(?:[a-zA-Z0-9.-]+|\[[0-9.]+\]))

to grab anything that could be an email address.

  ([a-zA-Z0-9!#$%&'*+-/=?^_`{|}~.]+\@(?:[a-zA-Z0-9.-]+|\[[0-9.]+\]))

Regular expression visualization

Debuggex Demo

Java regex for removing all characters except a pattern

3 Answers3

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