Java Programming

I have a very peculiar issue with a program I've made for a class. We were allowed to work with a partner on this project, and I was optimizing the code to make it run faster. I got to a certain point where I couldn't think of anything else to do, and it was running at about 2.5 seconds. I added it to Dropbox for my partner to download and check out, and when he ran it, he got a time of 0.5 seconds. Same exact code.

We've tried a few things such as re-uploading from both ends to see if there was some difference. I've re-installed eclipse and tried a different version and re-installed the latest JDK. I downloaded the Eclipse IDE for Java developers. That didn't solve the issue. So then I tried compiling the program with javac from the command prompt and running the program that way. This still gave me a time of around 2.5 seconds. I ran the Windows Experience index to see if my computer could have something wrong with it, but it came up with numbers slightly better than before. So it can't be anything wrong with my actual system. I haven't noticed a decrease in performance. So this narrows everything down to the Java environment itself.

We know the program works. It's already been submitted, graded, and returned and like I said, it runs extremely efficiently on my partner's computer. I just can't think of ANY REASON at all this program is running more slowly on my computer. Have any of you encountered an issue like this? I don't want anything to plague me for future projects.

Thanks for any ideas or assistance!
-Cole