Performance wise, is it better to call the length of a given array every time or store the length in a variable and call that variable every time?

I call on the length of a given array a lot and I was wondering if it is better to keep calling it numerous times (50+ times currently, but it keeps growing) or is it better to just store the length in an integer and use that integer every time.

If I am unclear in what I am saying, consider the following:

I have a String array:

String[] str = new String[500]; //The length is actually dynamic, not static

Of course, I put some values into it, but I call on the length of the string all the time throughout my application:

int a = str.length;
int b = str.length;
int c = str.length;
int d = str.length;
int e = str.length;

and so on...so is it better to do this: (performance wise, don't care about memory as much)

int length = str.length;
    int a = length;
    int b = length;
    int c = length;
    int d = length;
    int e = length;

Thanks.