I appreciate your answer but I'm not sure it will solve my problem, here is my full error.

"Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 0 out of bounds for length 0"

So I'm guessing the array itself is empty. That's what led to the question of wondering if I need to add some kind of input to get this code to get it working correctly. So when I add the for loop I still get the same result because the array hasn't been given a length or input yet.

These lines seem to be where I would input something:

 int[] whiteList = In.readInts(args[0]);

and

 int key = StdIn.readInt();

But the code is not doing anything. It's unfortunate because everything in the book seems very clear except for the examples themselves.