Java regular expression to validate username

Question

I am trying to use a username chain in Java with the following rules:

• Length> = 3
• Valid characters are: az, AZ, 0-9, periods, dashes, and underscores.

Can someone help me with regex?

Answer 1

try this regex: ^ [A-Za-Z0-9 ._-] {3} $

Answer 2

Sarkiroka's solution is correct, but forgot the dash, and the dot must be escaped.

You must add as \ to avoid this, but remember that in Java, the backslash itself is used to exit, so if you write a regular expression in a java file, you should write

String regex = "[a-zA-Z0-9\\._\\-]{3,}"; 

Note the double backslash.

Answer 3

BTW, if there is an additional requirement: the start 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 } 

See an example here .

Answer 4

What about:

  username.matches("[a-zA-Z0-9.\\-_]{3,}")