My program is turning against me! please help

Question

Background: Last year, I was in Comp. Sci. 1 at my high school. I tried to make a humongous game that I only partially got finished for my final project. Now, a year later, after I forgot most of java, and all of what I had written, I am trying to improve it.
Problem: There are various problems. On my computer at home, the program just stops after I work with it enough. No errors, no graceful shutdown, it just comes to a complete stop so I have to log out/in to fix it. Also, a canvas in my game seems to have to problem of, every once in a while, returning null when I call get getGraphics(). But that only happens like 1 out of 10 times I run it. Also, sometimes it give me an error to the effect of "null pointer exception", but it neglects to tell me where in my program the error came from, it just lists about half a dozen instances of threads (or I think thats what it is). How can I fix any of these problems? Thanks,
Eric

Answer 1

My first thought on reading your subject line is to tell you to unplug skynet now before it gets into the network...
That aside you haven't given us a whole lot to work from but I can tell you this. You have a variety of seemingly fatal threading issues and problems. I must warn you that these sorts of issues are often only resolvable by a ground up re-write because it's possible that your threading model is just that much of a mess.
Anyway it's threading related based on your symptoms because of two things
- the kind of freezing you describe
- it appears from the rest of your post that threads are deadlocking. Essentially thread A is holding on to Object apple and wants to use object Pear. But thread B is holding on object Pear and won't let go until it gets Object apple
Anyway you'll have to start posting your threading relevent code if you want more help. Please make sure to use the code tags. I'll tell you right now though thread deadlock all over the place with whatever race conditions etc you are experiencing is not a good sign.
Not to feel bad. Threading is not an easy topic to learn, which is why it's best to start small. But we'll see what we can do.