// Learning Processing
  // Daniel Shiffman
  // http://www.learningprocessing.com
  
  // Example 9-11: Resizing an array using append()
  
  Ball[] balls = new Ball[1]; // We start with an array with just one element.
  float gravity = 0.1;
  
  void setup() {
    size(200,200);
    smooth();
    
    // Initialize ball index 0
    balls[0] = new Ball(50,0,16);
  }
  
  void draw() {
    background(255);
    
    // Update and display all balls
    for (int i = 0; i < balls.length; i ++ ) { // Whatever the length of that array, update and display all of the objects.
      balls[i].gravity();
      balls[i].move();
      balls[i].display();
    }
  }
  
  void mousePressed() {
    // A new ball object
    Ball b = new Ball(mouseX,mouseY,16); // Make a new object at the mouse location.
    balls = (Ball[]) append(balls,b);
  
    // Here, the function, append() adds an element to the end of the array. 
    // append() takes two arguments. The first is the array you want to append to, and the second is the thing you want to append. 
    // You have to reassign the result of the append() function to the original array. 
    // In addition, the append() function requires that you explicitly state the type of data in the array again by putting the 
    // array data type in parentheses: (Ball[]) This is known as casting.
  }