Polymorphism

Question

Hai All
I hava doubt regrading polymorphism concept . Firstly please look in to this program then explain me clearly
class Shape
protected Color color;
protected int x, y;
Shape (Color c, int xPosition, int yPosition)
color = c;
x = xPosition;
y = yPosition;
} // constructor
public void drawShape (Graphics g)
g.setColor (color);
g.drawString ("Shape", x, y);
} // method drawShape
} // class Shape
class Circle extends Shape
private int radius;
Circle (Color c, int x, int y, int r)
super (c, x, y);
radius = r;
} // constructor
public void drawShape (Graphics g)
g.setColor (color);
g.fillOval (x, y, 2*radius, 2*radius);
} // method drawShape
} // class Circle
class Rectangle extends Shape
private int width, height;
Rectangle (Color c, int x, int y, int w, int h)
super (c, x, y);
width = w;
height = h;
} // constructor
public void drawShape (Graphics g)
g.setColor (color);
g.fillRect (x, y, width, height);
} // method drawShape
} // class Rectangle
if i want to access Circle drawShape method i can do like this :
Circle ob=new Circle();
ob.drawShape();
likewise i can access Rectangle drawShape method i can do like this :
Rectangle ob=new Rectangle ();
ob.drawShape();
instead of doing , some one trying to access some this way
Shape ob=new Rectangle();
Rectangle rectangle=(Rectangle)ob;
rectangle.drawShape();
Circle circle=(Circle)ob;
circle.drawShape();
please explain me what exact different between this two way . i hava been trying to find exact solution for this but i am not able .
Thanks
Selvakumar

Answer 1

I don't know what your question is. The following are the same.
Circle c = new Circle(...);
c.drawShape(g);
Shape shp = new Circle(...);
shp.drawShape(g);..because in both cases you are sending the same object the same message: draw yourself!