Hi,
I've been trying to solve this for a few days and can't seem to so I figured I'd come and ask to see if anyone knew where I was going wrong and what I should be doing.

Basically I'm creating an array of Objects, which are balls that travel back and forth on the screen. I've added a random number feature in the code and when the random number generated equals 3 then I want to update the array of objects, expanding it by one and adding a new ball into the Array and then onto the screen.

My current main script looks like this:

1. 
   int numBalls = 8; // variable to hold the initial size of array
   Ball[] balls = new Ball[numBalls]; // array to hold ball objects
   Ball addOneBall;
   
   void setup()
   {
     // set up screen
     size(500, 500);
     smooth();
     noStroke();
   
     // for loop to fill array with  balls
     for (int i = 0; i < balls.length; i++)
     {
       balls[i] = new Ball();
     }
   }
   
   void draw()
   {
     fill(255, 200); //white see-through background
     rect(0, 0, width, height); // draw rect instead of background so we can use alpha to give comet tail effect on balls
   
     int addOne = int(random(100)); //generate a random number to use in a conditional in a moment
     println("random number is " + addOne); //print random number to terminal to monitor
   
     //conditional statement if random number is three...
     if (addOne == 3)
     {
       int currentLength = balls.length; // Create and int of the value of the current length of the array
       println("Current length of balls array is " + currentLength); ///print value to terminal
      
       balls = (Ball[]) expand(currentLength+1); //extend the current array by one
       addOneBall = new Ball(); // Create new Ball
       balls = splice(balls, addOneBall, currentLength); //splice addOneBall and balls array, placing addOneBall in the last position of the array
     }
   
     //
     for (int i = 0; i < balls.length; i++)
     {
       balls[i].move();
       balls[i].updateMe();
       balls[i].display();
     }
   }
   
   

my Class for the Ball looks like this:

1. class Ball
   {
     float x, y;
     float diam;
     float radius;
     float speed;
     int dir =1;
     int decision = int(random(-1, 1));
     color shade;
   
     int addABall = 1;
   
       Ball()
     {
       x = random(width);
       y = random(height);
       diam = (random(10)+10);
       radius = diam/2;
       speed = random(5);
     }
   
   
     void move()
     {
       x+=(speed * dir);
       if ((x > width) || (x< 0))
       {
         dir *= -1;
       }
     }
   
     void updateMe()
     {
       boolean touching = false;
       for (int i = 0; i< balls.length; i++)
       {
         Ball otherBall = balls[i];
         if (otherBall != this)
         {
           float dis = dist(x, y, otherBall.x, otherBall.y);
           if ((dis - radius - otherBall.radius) < 0)
           {
             touching = true;
             break;
           }
         }
       }
       if (touching)
       {
         shade = color(200);
         display();
       }
       else
       {
         shade = color(0);
         display();
       }
     }
   
     void display()
     {
   
       fill(shade);
       ellipse(x, y, diam, diam);
     }
   }   
   
   

When I initially tried to solve this problem I figured I'd have to reiterate the for loop in setup every time I wanted to lengthen the array. Then I realised that 1. this was a bad idea because its inefficient & I'd loose the location of the balls on screen and 2. a more sensible thing to do would be to simply extend the size of the Array by one and then stick a new ball object in the new empty slot. I try to do this in the main code with the following code inside the if statement in void loop:

1. int currentLength = balls.length; // Create an int of the value of the current length of the array
       println("Current length of balls array is " + currentLength); ///print value to terminal
      
       balls = (Ball[]) expand(currentLength+1); //extend the current array by one
       addOneBall = new Ball(); // Create new Ball
       balls = splice(balls, addOneBall, currentLength); //splice addOneBall and balls array, placing addOneBall in the last position of the array

but when I try to do this I get an error telling me I can't convert from Object to addOneBall.Ball[]; I don't fully understand the error message. I've took the syntax of the code from the example given in the processing reference for the expand() method which is available here: http://www.processing.org/reference/splice_.html
and the expand() method which is available here: file:///Applications/Processing.app/Contents/Resources/Java/modes/java/reference/expand_.html

Can someone tell me how to make my code work in the way I want it and where I'm going wrong in terms of how I'm approaching this problem?

Thanks for reading

Bunzy