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thanks, i think that will work.

Another way to handle this is simply <Code Omitted>This will always return the remainder portion of the division. As short as this is, dropping the method and using (i % i2) in the calling method might be preferable.

Briefly, you first want to import the List interface (at the top of your class): <Code Omitted> Then you do something like: <Code Omitted> Hopefully that's enough to get you started!

Well, I have finally figured out a way. Problem is I'm not sure how to delete this post so for now it will remain haha.

Thank you! Now I undersdand! Another question about mouse event, how can I find out if the mouse is hold on sth. I tried to figgure it out by getX() and getY(),is there some good iead?Thanks

I tried and it works, thanks

Thanks for all the help! I put a new public void called CheckMouse in ball.class and called it in Act(), and it worked perfectly . I also am making a limit to the ball count so that it doesn't lag. For some odd reason though, this isn't having the effect I thought it would. if(ballCount < 6) { getWorld().addObject(new Ball(), mouseX, mouseY); ballCount = (ballCount + 1); }

It's hard to tell without seeing what you did. Can you show us the code snippet that you think should make your variable change?

There is a demo for a side scrolling background here: http://www.greenfootgallery.org/scenarios/243 You could look at this and adapt it to scroll vertically.

Good that you found it. One thing to keep in mind is that the error message is not always very precise or helpful - looking around the area of the error often shows what's wrong.

Thanks :D!

Take a look at this tutorial which does exactly what you are describing. http://www.greenfoot.org/doc/howto-1