Ball Object Which Implements Runnable Interface And Traces Various Positions Of A Ball

a) I have a Ball Object which implements the Runnable interface and traces the various positions of a ball.

b) I then have a Ball_Bounce JPanel inside a JFrame which creates two instances of the Ball object and then paints them to the JPanel.

As per my understanding, when the main() program in Ball_Bounce.java is started, there a total of three threads running in this program, one for each ball and one for the main(). What I cannot understand is whenever the balls collide, I end up getting the "Collision" message twice even though the collision is checked only in the main() thread.

[#]public class Ball implements Runnable
{
private boolean xUp, yUp, xUp1, yUp1;
private int x, y, xDx, yDy;
private final int MAX_X = 500, MAX_Y = 500;
private boolean flag = true;
private static Thread ball;
 
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