I'm trying the username chains in Java with following rules:
- Length >=3
- Valid characters: a-z, A-Z, 0-9, points, dashes and underscores.
Could someone help me with the regular expression?
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4 Answers
try this regular expression:
^[a-zA-Z0-9._-]{3,}$
3 Comments
Grambot
[a-zA-Z0-9_.-]{3,} is more accurate as he wants to include "points dashes and underscores". See stackoverflow.com/questions/3028642/…
RichieHindle
@TheCapn: I fixed it as you were writing your comment. :-)
ridgerunner
You should add start
^ and end-of-string $ anchors for validation regexes like these (although the Java .matches() method does do this implicitly).Sarkiroka solution is right, but forgot the dash and the point should be escaped.
You should add as \ to escape it, but mind that in Java the backslash is itself used to escape, so if you are writing the regex in a java file, you should write
String regex = "[a-zA-Z0-9\\._\\-]{3,}";
Note the double back slashes.
1 Comment
Qtax
No need to escape
., and probably no need to escape - either since it's last in the class (but I'm unsure how Java handles this).BTW, if there is an extra requirement: the starting letter of the username must be a character, you can write
try {
if (subjectString.matches("\\b[a-zA-Z][a-zA-Z0-9\\-._]{3,}\\b")) {
// Successful match
} else {
// No match
}
} catch (PatternSyntaxException ex) {
// Invalid regex
}
Based on an example here.
Comments
What about:
username.matches("[a-zA-Z0-9.\\-_]{3,}")
2 Comments
8vius
I don't think you have to escape the .-_ characters if they're in the [] but other than that it looks fine, though you should've commented on Richie's answer before posting your own.
Emmanuel Bourg
The dash must be escaped, but it doesn't matter for the dot.