Exercise$6\mathrm{.}68$

Change the method bounce in class BallDemo to let the user choose how many balls should be bouncing.

For this exercise, you should use a collection to store the balls. This way, the method can deal with $1,3,$ or $75$ balls$$any number you want. The balls should initially be placed in a row along the top of the canvas.

Which type of collection should you choose? So far, we have seen an ArrayList, a $$HashMap$,$ and a HashSet. Try the next two exercises first, before you write your implementation.