newInstance() method

Processing Coding Questions
1

Hello everybody!

I think there is a problem in Processing with the method newInstance().

If I run this simple example:

void setup(){
  try{
  Test t = Test.class.newInstance();
  }catch(Exception e){
  e.printStackTrace();
}
}

void draw(){
}


class Test {
  public Test() {
  }
}

I receive the following error:

ava.lang.InstantiationException: sketch_201110a$Test
at java.lang.Class.newInstance(Class.java:427)

Do you have any ideas?

Many thanks.
Alberto

2

Hello and welcome to the forum!

Great to have you here!

That’s how I’d do it.

Read more here: https://www.processing.org/tutorials/objects/

Warm regards,

Chrisir

Test t; 

void setup() {
  size(600, 600);
  t = new Test();
}

void draw() {
  //
}

// ===============================================================

class Test {
  //
  Test() {
  }
  //
}//class
3

Yes. That is the “classic” way to do it. However, there are cases in which you have access only to the interface of a class, and the only way to instantiate the class is using the method newInstance.

In Java the piece of code that I posted works…

1 Like
4

Hi @alb85,

Not sure if this is what you are looking for,

This case implements an interface and a class is then defined and used. To create a new instance of a class Test, call Test_name = new Test();


interface Dot {
  void move();
  void display();
}

class CircleDot implements Dot {
  float x = 50;
  float y = 50;

  void move() {
    x = x + random(-1, 1);
  }

  void display() {
    ellipse(x, y, 16, 16);
  }
}

class SquareDot implements Dot {
  float x = 50;
  float y = 50;


  void move() {
    y = y + random(-1, 1);
  }

  void display() {
    rect(x, y, 16, 16);
  }
}


SquareDot sq;
void setup() {
  size(100, 100);
  sq = new SquareDot();
}

void draw() {
  
  sq.move();
  sq.display();
}
1 Like
5
1 Like