Question

Writing a simple regex, but I’ve never been very good at this.

What I’m trying to do is check a string (filename) to make sure it only contains a-z, A-Z, 0-9 or the special characters underscore (_) period (.) or dash (-).

Here’s what I have

if(filename.length() < 1 || !filename.matches("^[a-zA-Z0-9[.][_][-]]+"))
   return false;
else
   return true;

This appears to work, but does not look very elegant to me. Is there a better / more readable way to write this?

Thanks in advance! Just trying to learn how to write these buggers better.

-Will

Answer 1

You don’t need to use [] inside character class.

So, you can write:

^[-a-zA-Z0-9._]+

Also, you can use \\w instead of a-zA-Z0-9_.

So, the regexp would be:

^[-\\w.]+

Also, this regexp will match a string like StackOverflow 22.10$$2011 by consuming StackOverflow 22.10. If you need your string to consist completely of those character, you should end the pattern with $ – the end of the string:

^[-\\w.]+$