I'm trying to create an information display that consists of ellipses that rearrange themselves depending on button presses.  I want them to be animated to create continuity.  I've created an object class for the ellipses but it doesn't seem to be working.  I'm posting a simplified version of my code.

movingBall a1;

void setup() {
 size(500, 200);
 smooth();
}

void draw() {
 background(0);
 stroke(255);
 fill(255);
 
 line(0,100,500,100);
 
a1 = new movingBall(50,500);
a1.display();



}

class movingBall {
 int s;
 int y = 100;
 int d;


movingBall(int xpos, float dpos) {
 s = xpos;
 d = int(dpos);
}

void display() {
ellipse(s,y, 20, 20);

if (d<0) {
   d=d+100;
 } else if (d>500) {
   d=d-100;
 } else if(s>d) {
   s--;
 } else if (s<d) {
   s++;
 }
}
}

I'm an art student, getting into programing.  So I'm sure it's something simple that I just don't know.  Thank you.

That worked.  Thank you so much.  and sorry about not being more specific.