code: public boolean contains(float x, float y) 
      { 
          float xDelta = x - getCenterX(), yDelta = y - getCenterY();
          return xDelta * xDelta + yDelta * yDelta < getRadius() * getRadius();
      }
docs: Check if a point is contained by this circle
  
  @param x The x coordinate of the point to check
  @param y The y coorindate of the point to check
  @return True if the point is contained by this circle