Checkstyle method name rule regexp modification

Question

I am running Sonar and checkstyle has a regexp rule like this:

^[a-z][a-zA-Z0-9]*$

I would like to modify it so that one or more underscores are allowed. How would I change this? Thanks!

Answer 1

Those are character classes.

If you want to allow underscores anywhere:

^[a-z_][a-zA-Z0-9_]*$

If you want to allow underscores anywhere except the first character:

^[a-z][a-zA-Z0-9_]*$