Ball class Processing complete

class Ball{
  //instance variables
  private int diameter;
  private color colour;
  private int x, y;
  private int xVel, yVel;

  //methods/abilities

  //draw the ball on the screen
  public void display(){
    fill( colour );
    ellipse(x, y, diameter, diameter);
  }

  //make the ball "move": change the x and y by their respective velocities
  public void move(){
    x += xVel;
    y += yVel;
  }

  //make the ball "bounce": make the xVel/yVel flipflop depending on wall hit
  public void bounce(){
    if( x >= width || x <= 0 ) xVel = -xVel;
    if( y >= height || y <= 0 ) yVel = -yVel;
  }

  //constructor - make a random ball
  public Ball(){
    x = width / 2;
    y = height / 2;
    diameter = (int)(Math.random() * 76 + 25);//25 - 100
    xVel = (int)(Math.random() * 11 - 5);//-5 - 5
    yVel = (int)(Math.random() * 11 - 5);//-5 - 5
    colour = color( (int)(Math.random() * 256), (int)(Math.random() * 256), (int)(Math.random() * 256));
  }
}