Drawing on canvas

import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;
 
 
class Test{
 
 
    public void paint(Graphics g) 
    {
         g.drawLine(150, 500, 150, 200);
         g.drawLine(01, 200, 644, 200);
         g.drawLine(430,200,430,500);
         g.drawLine(300,200,300,002);
 
         for ( int k = 0; k <= 100; k++)
         {
              int x = (int) (Math.random() * 200);
              int y = (int) (200 + Math.random() * 400);
 
              g.drawOval(x, y, 12.5, 12.5 );
 
          }
        }
 
 
   public static void main(String args[]){
 
      JFrame frame = new JFrame("HelloWorld");
      frame.setSize(600,400);
      frame.setLayout(null);
 
      JButton b1 = new JButton(" one ");
      JButton b2 = new JButton(" two ");
      JButton b3 = new JButton("three");
 
      b1.setSize(b1.getPreferredSize());
      b1.setLocation(20, 20);
      frame.add(b1);
      b2.setSize(b2.getPreferredSize());
      b2.setLocation(20, 50);
      frame.add(b2);
      b3.setSize(b3.getPreferredSize());
      b3.setLocation(20, 80);
      frame.add(b3);
      frame.paint();
      frame.setVisible(true);
 
   }
}