Regex for alphanumeric password, with at least 1 number and character

Question

Need help with a regex for alphanumeric password, with at least 1 number and character, and the length must be between 8-20 characters.

I have this but doesn\'t seem

Answer 1

Why not just use a handful of simple functions to check?

checkPasswordLength( String password);
checkPasswordNumber( String password);

Maybe a few more to check for occurrences of the same character repeatedly and consecutively.