Beginning coding... And running into problems

Now that I had my idea sorted, I began to start coding for my project. Tutorial 8 on bouncing balls and arraylists was a huge help in this. However in my concept, I had envisaged the emitted balls to have been able to bounce of the rectangles in the lower half of the page and create a sort of randomly induced interaction. The actual coding of this however was just far too complicated and I decided to alter my idea so that the balls will just pass through the lines and a resulting sound will be heard.

The balls just bounce through the rectangles now instead of bouncing off them