code: @Pure
  	public IntegerProperty radiusProperty() {
  		if (this.radius == null) {
  			this.radius = new SimpleIntegerProperty(this, MathFXAttributeNames.RADIUS) {
  				@Override
  				protected void invalidated() {
  					if (get() < 0) {
  						set(0);
  					}
  				}
  			};
  		}
  		return this.radius;
  	}
docs: Replies the property that is the radius of the circle.
  
  @return the radius property.