A java swings program on shapes

[2384443]

Hi everyone, i need your help.. I want to draw a circle,square and rectangle on Jframe on a click of a button.. This program was asked in my test paper, i couldn't get it right though bt i wanna know what my mistake is.. Plz help me..

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class CRS extends JFrame implements ActionListener
{
JButton b1,b2,b3;
Graphics g;
Container con;

    public CRS()
    {
    super("Draw Circle in JFrame");
    con=getContentPane();
    con.setLayout(new FlowLayout());

    b1=new JButton("Circle");
    b2=new JButton("Rectangle");
    b3=new JButton("Square");

    con.add(b1);
    con.add(b2);
    con.add(b3);

    b1.addActionListener(this);
    b2.addActionListener(this);
    b3.addActionListener(this);
    }

            public void Circle()
            {
            g.drawOval(50,50,100,100);
            }

                public void Rectangle()
                {
                g.drawRect(250,350,80,40);
                }

                    public void Square()
                    {
                    g.drawRect(100,200,100,100);
                    }

    public void paint()
    {
    Circle();
    Rectangle();
    Square();
    }

        public void actionPerformed(ActionEvent ae)
        {
            if(ae.getSource()==b1)
            {
                try
                {
                Circle();
                }

                    catch(Exception e1) 
                    {
                    JOptionPane.showMessageDialog(this,"Error");
                    }
            }

            if(ae.getSource()==b2)
            {
                try
                {
                Rectangle();
                }

                    catch(Exception e2) 
                    {
                    JOptionPane.showMessageDialog(this,"Error");
                    }
            }

            if(ae.getSource()==b3)
            {
                try
                {
                Square();
                }

                    catch(Exception e3) 
                    {
                    JOptionPane.showMessageDialog(this,"Error");
                    }
            }

}

public static void main(String args[])
{
CRS aa=new CRS();
aa.setVisible(true);
aa.setSize(400,400);
aa.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}

[JamesCherrill]

You can't draw things in Swing by just drawing to some random Graphics. You have to fit your drawing into the existing Swing mechanisms. This tutorial explains what you need to know.
If that leaves you with any further questions, just ask them here.