Why does only one object appear?

Lucas_p

When I run the code there should be two balls moving, but it only shows one ball. I'm sure it's a dumb mistake, but I haven't been able to figure it out.

circulo c;
circulo c1;
void setup(){
  size(700,500);
  c = new circulo(30,width-1,0,2,3);
  c1 = new circulo(25,0,height/2,4,5);
}

void draw(){
  background(255);

  c.move();
  c.display();
  c1.move();
  c1.display();
}

class circulo{

  float x;
  float velocidadX;
  float velocidadY;
  float y;
  float d;

  circulo(float diametro, float posX, float posY, float vx, float vy){
    d = diametro;
    x = posX;
    y = posY;
    velocidadX = vx;
    velocidadY = vy;
  }

  void move(){    
      y = y + velocidadY;
      x = x + velocidadX;
  if (x > width){
    velocidadX = -velocidadX;
  }
  if (x < 0){
    velocidadX = -velocidadX;
  } 

  if (y > height){
    velocidadY= -velocidadY;
  }
  if (y < 0){
    velocidadY= -velocidadY;
  }  
 }

  void display(){
  background(10);
  ellipse(x, y, d, d);  
  }

}

`

GoToLoop

background() erases everything that has been drawn before! L-)
And you've got background() inside your method display()! #-o

BtW, classes and interfaces should follow the UpperCaseNaming convention. ~O)
So class circulo should be renamed as Circulo. ;)