Question

I have a simple java application that tests for collision off 4 walls and off each of the 10 balls… I have the walls figured out but circle-to-circle doesn’t seem to work for me. When I run this segment along with the rest of the program I get 10 very shaky circles (that appear to be colliding with themselves) and they don’t move very much at all. If I take this segment out I get 10 circles that move smoothly and collide off of the 4 walls. Can someone tell me what might be causing the problem? THANKS

for (int j = 0; j < ballnum; ++j) {
    for (int k = 0; k < ballnum; ++k) {
        if (Math.sqrt((Math.pow(balls[j].givebackpoint().x - balls[k].givebackpoint().x, 2))
            + (Math.sqrt(Math.pow(balls[j].givebackpoint().y - balls[k].givebackpoint().y, 2)))) <= 2 * RADIUS) {
            if (balls[j].givebackangle() >= 180) {
                balls[j].setangle(balls[j].givebackangle()-180);
                                        }
            else{
                balls[j].setangle(360-balls[j].givebackangle());
                }
            }
        }
    }

Answer 1

You’re checking each ball against itself.

You need to skip running the tests when j == k with a line like this at the top of your inner for loop:

if (j == k)
    continue;