Regular Expression in Java for validating username

Question

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.

Answer 1

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.