This example is for Processing 3+. If you have a previous version, use the examples included with your software. If you see any errors or have suggestions, please let us know.

Multiple constructors

A class can have multiple constructors that assign the fields in different ways. Sometimes it's beneficial to specify every aspect of an object's data by assigning parameters to the fields, but other times it might be appropriate to define only one or a few.

Spot sp1, sp2;

void setup() {
  size(640, 360);
  // Run the constructor without parameters
  sp1 = new Spot();
  // Run the constructor with three parameters
  sp2 = new Spot(width*0.5, height*0.5, 120);

void draw() {

class Spot {
  float x, y, radius;
  // First version of the Spot constructor;
  // the fields are assigned default values
  Spot() {
    radius = 40;
    x = width*0.25;
    y = height*0.5;
  // Second version of the Spot constructor;
  // the fields are assigned with parameters
  Spot(float xpos, float ypos, float r) {
    x = xpos;
    y = ypos;
    radius = r;
  void display() {
    ellipse(x, y, radius*2, radius*2);