Hi there, I've just been looking at the example programs and noticed a couple of things in the "Objects" code:

http://processing.org/learning/examples/objects.html

class MRect has an unused member variable: float side

The display() function draws rectangles starting with x-coordinates of
   xpos+(i*d*w)

it would make more sense to use
   xpos + (i * (d+w))

You might then want to adjust the parameters passed to the MRect constructor for the initialisation of r1,r2,r3,r4 in setup() depending on the desired result.