I'd say you're getting the NullPointer because you haven't initialized the SingleSpace objects in your Grid. You need to initialize them before trying to operate on them, otherwise you're trying to perform the operation on a null object, and thus throwing the exception.

So, a fix for that might look something like this:

public Grid(int rows, int cols){
for(int i = 0; i < 10; i++){
        for(int j = 0; j < 10; j++){
               playerBoard[i][j] = new SingleSpace();
               playerBoard[i][j].setValue(-1);
        }
    }
}

You also have other issues with how big you want your constructor to make the Grid. You currently have 3 options in your code: the two constants ROW and COLS, hard coded values in the for loops, and passed parameters. It's best to decide on this now, so as to avoid confusion later.

EDIT: The reason it worked when using int is that int has a default value of zero, as discussed here. Objects have a default value of null.

Here's a relevant link to a description of the method: W3 School Page

I would look at that, and look at your if statement in flip(). Your comparison is your problem.

Pay special attention to the range of the random method and the fact that you want a given result half of the time.

That's all I've got for you at a glance. For displaying results, however, someone else will have to help you. Unfortunately, I'm not that familiar with javascript.

The job I just started really promotes this style of coding, but didn't use it at all in college. Thus, I put "No, (some other reason).

It's quite a struggle to try and flip your mindset to test-driven when you're not used to it, but I can certainly see the benefits. Knowing what you have to satisfy, test-wise, is definitely a good way to approach a development problem. I'm definitely going to try and use it going forward.

Alright. So that markup invalidator site is cool! Didn't know about that.

Anyway, after fixing that, stuff, I moved the beginning and end of the form outside of the div, and things worked. Thanks a bunch, again, for the help!

I'll shoot you a pm with the link. At this point, it's not hooked up to anything important, so go nuts. The body of the page is php generated, so if you want to see how that stuff is generated, let me know. Thanks a bunch!