Regular expression to select all whitespace that isn't in quotes?

I'm not very good at RegEx, can someone give me a regex (to use in Java) that will select all whitespace that isn't between two quotes? I am trying to remove all such whitespace from a string, so any solution to do so will work.

For example:

(this is a test "sentence for the regex")

should become

(thisisatest"sentence for the regex")