Hi, I would suggest using an ArrayList instead of an array.
They work pretty much the same but are a little easier to manipulate.

Here's a detailed example:
-----------------------------------------------------------
ArrayList arrayName = new ArrayList();

void setup() {
 size(400,400);
 background(0);
 
 arrayName.add(new className());
 
  println(arrayName.size()); //returns the length of the ArrayList
  println(arrayName.get(0)); //return the item at a certain position (since you stored a class, it returns some funky stuff!)
}
 
void draw() {
  for ( int i = 0; i<arrayName.size(); i++ ) {
   ((className)arrayName.get(i)).draw();  //calls the function over and over
 }
}

class className{
 int variable;
 
 className() {
   variable = int(random(10));
 }  
 
 void draw() {
   println(variable);
 }
}
-----------------------------------------------------------

To get all the method, visit: http://java.sun.com/j2se/1.4.2/docs/api/java/util/ArrayList.html

Cheers!

expand() works on arrays of objects as well, you just have to cast the values returned because the function returns Object[].

so in your code, that would look like:

drawings = (drawing[]) expand(drawings, drawings.length+1);

however, expanding by 1 is inefficient. it's better to keep a count of how many values are in there, and just double the size of the array (this is the default that expand will use if no size is specified).

drawings = (drawing[]) expand(drawings);
drawings[drawingCount++] = new drawing();

ArrayList works fine to, but using arrays is faster in cases where you have a lot of values. for your particular code, the difference will not be apparent.

take array named "drawings" and expand it's length to be 1 longer than before ("drawings.length+1"). the result will be passed back as Object[], so cast it to be of type "drawing[]". assign the result to the variable named "drawings" ("drawings = ").

clear?

Hey, I'm trying to do something very similar, but I keep getting an ArrayIndexOutOfBoundsException.

I thought this would work...
Code:

import processing.opengl.*;

float radius;
PulseCircle pulse[] = new PulseCircle[1];
PImage pulseCircleImg;
int PulseCircleCount = 1;

void setup() {
  size(400,400,OPENGL);
  hint( ENABLE_OPENGL_4X_SMOOTH );
  textureMode(NORMALIZED);
  pulseCircleImg = loadImage( "glowCircleThin.png" );
}

void draw() {
  background(0);

  translate(width/2, height/2);
  
  if( keyPressed ) {
    pulse = (PulseCircle[]) expand(pulse, pulse.length+1);  
    pulse[pulse.length] = new PulseCircle(0,0);
    
    //pulse.start(0,0);
    println(pulse.length);
    
  }
  
  
  //pulse.update();
  //pulse.display();
  
}


class PulseCircle {
  float x, y;
  float pulseRadius;
  boolean on = false;

  // Constructor
  PulseCircle(float xpos, float ypos) {
    x = xpos;
    y = ypos;
    println("PulseCircle");
  }

  void start(float xpos, float ypos) {
    x = xpos;
    y = ypos;
    on = true;
    pulseRadius = 0;
    println("Start");
  }

  void update() {
    if (on == true) {
	pulseRadius += 5;
	println("Update : True");
    }
    if (pulseRadius > 500) {
	pulseRadius = 0;
	on = false;
	println("Update : False");
    }
  }

  void display() {
    if (on == true) {
	pushMatrix();
	beginShape();
	texture(pulseCircleImg);
	vertex(-(pulseRadius), -(pulseRadius), 0, 0, 0);
	vertex((pulseRadius), -(pulseRadius), 0, 1, 0);
	vertex((pulseRadius), (pulseRadius), 0, 1, 1);
	vertex(-(pulseRadius), (pulseRadius), 0, 0, 1);
	endShape();
	popMatrix();
	//fill(255);
	//ellipse(0,0,pulseRadius,pulseRadius);
	println("Display");
    }
  }
}