Where do I go wrong here?

I do have
Code:
String[] car = null;
car[0]  = "test";
I get this error:
Exception in thread "main" java.lang.NullPointerException

Does this mean that I have to throw a special Exception, how can i find out which one if that is the case?

At top of the code i have this as I usually do:
Code:
public static void main(String[] args) throws IOException {
Thankful for any help.