" I get an error."
We are not psychic nor in front of your computer and cannot guess what this error is...
We cannot even run your code snippet to test it!
At least, I can make one similar.
Don't forget: size() must be the first line of setup()!

Test code:

1. void setup()
2. {
3.   size(400, 400);
4.   String url = "http://maps.googleapis.com/maps/api/streetview?size=400x400&location=40.720032,%20-73.988354&sensor=false";
5.   PImage img = loadImage(url, "JPG");
6.   image(img, 0, 0);
7. }

I added the "JPG" parameter after I saw the error message: "NullPointerException: Could not find a method to load"
Indeed, Processing hasn't found an extension in the path / URL, so it doesn't know which image format to use. My additional parameter helps it to find out.

Hi PhiLo,

Thanks so much for the help. I didn't realize you could add extra parameters to loadImage(). I guess I thought that my error was so obvious that you didn't need to run the code.

Thanks again!

No, I had to write the code above to see the error. That's why it can be nice, when asking a question, to give a simple sketch reproducing the problem with the smallest amount of code, like not needing unrelated libraries (XlsReader!) and such. It helps in getting quick and accurate answers.