I would like a little help about regex matter in Java.

Supposing that I want to check if a TextField contains only Strings not Numbers, which is the code to accomplish this?

I tried :
String str = new String();
if (str.matches("[a-zA-Z]")) {}
else {}

When it comes for the user to enter more than one character in the TextField, it doesn't work. It works only for one character!

Any help appreciated,