Java Regex - alphanumeric, allowing leading whitespace but not blank string

Question

I've been trying to make a java regex that allows only alphanumeric characters, which can have white spaces, BUT the whole string cannot be blank...

Few examples..

" hello world123" //fine
"hello123world" //fine
"hello123world " //fine
"    " //not allowed

So far I've gotten ^[a-zA-Z0-9][a-zA-Z0-9\s]*$ though this does not allow any leading whitespace and so any string with x number leading whitespace is not being matched.

Any ideas what I could add to the expression to allow leading whitespace?

Answer 1

How about just ^\s*[\da-zA-Z][\da-zA-Z\s]*$. 0 or more spaces at start, follow by at least 1 digit or letter followed by digits/letters/spaces.

Note: I did not use \w because \w includes "_", which is not alphanumeric.

Edit: Just tested all your cases on regexpal, and all worked as expected. This regex seems like the simplest one.