Processing | How to stop the ball from changing it's color - processing

Question

Here's a little code that I've written to get a ball bouncing in Processing. The ball should change it's color everything it bounces off the "ground" and become slower and slower and lay at the ground at the end.
But - and that's the problem I've got - the ball doesn't stops changing it's color at the bottom - and that means it didn't stops bouncing, right?
The question is: How do I tell the ball to stop and not to change it's color anymore?
float y = 0.0;
float speed = 0;
float efficiency = 0.9;
float gravitation = 1.3;
void setup(){
size(400, 700);
//makes everything smoother
frameRate(60);
//color of the ball at the beginning
fill(255);
}
void draw() {
// declare background here to get rid of thousands of copies of the ball
background(0);
//set speed of the ball
speed = speed + gravitation;
y = y + speed;
//bouce off the edges
if (y > (height-25)){
//reverse the speed
speed = speed * (-1 * efficiency);
//change the color everytime it bounces off the ground
fill(random(255), random(255), random(255));
}
//rescue ball from the ground
if (y >= (height-25)){
y = (height-25);
}
/*
// stop ball on the ground when veloctiy is super low
if(speed < 0.1){
speed = -0.1;
}
*/
// draw the ball
stroke(0);
ellipse(200, y, 50, 50);
}

Answer 1

The problem is that even though you are setting the speed to -0.1 when it is small, and y to height - 25, the very next pass through the loop adds gravity to speed and then speed to y, making y larger than height - 25 (by slightly more than 1 pixel) again. This makes the ball jump up and down through an infinite loop of hops of zero height.
You could use a threshold on the reflected speed. If it is below the threshold, stop the loop.
At the top of the file, add a line like
float threshold = 0.5; //experiment with this
Then in draw(), right after the line
speed = speed * (-1 * efficiency);
add the line
if(abs(speed) < threshold) noLoop();
In this case, you can throw away the if clause which checks when the speed is super-low.