A struct is basically a class with all attributes made public. e.g.

1. public class Circle {
2.       public float x;
3.       public float y;
4.       public float radius;
5. }

Or if you want to avoid instantiating the object make everything static.

Code Example

1. void setup() {
2.   println(Circle.x);
3.   println(Circle.y);
4.   println(Circle.radius);
5.   exit();
6. }
7. 
   
8. static class Circle {
9.   static float x = 20;
10.   static float y = 22;
11.   static float radius = 45;
12. }

Can you reassign static variables?  The 'static' sets them up to be the same value amongst all instantiations of a class, is that right?

The static solution answers your question about making a structure without instantiating a class.
But I fear the question hasn't much sense. Why to avoid making such instantiation?

And, yes, the values of static fields in classes are actually shared among all the instances of that class.

Well, as I'm still learning these things I'm just trying to figure out why/when to implement these things, and in the case of Processing, whether they can even be used.  I see the answer is 'no', and I'll continue to use classes here.