Of this abstraction. The values for getRadius() or getCircumference() in the above illustration could be stored straight, or they could be calculated, it doesn't make a difference for the caller; the setters may well or may not have Unwanted side effects; it won't make a difference to your caller. See https://propertyingurugram.in/m3m-india-to-invest-rs-700-crore-on-new-retail-real-estate-project-in-gurugram/