Of the abstraction. The values for getRadius() or getCircumference() in the above example could be saved directly, or they might be calculated, it does not subject to the caller; the setters could or won't have Unwanted effects; it isn't going to make a difference to the caller. See @michael-puckett-ii 's https://propertyingurugram.in/luxury-studio-apartments-fast-catching-up-in-gurugram/