Paint Method

I try to draw the line like this on the screen, but when some menu show
up my line is not draw correctly. Anyone know how to solve it thankyou.

Follow this code. I tried paint() and paintComponent() but it doesn't
work both.

Code:

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;

import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;

public class TestPaint extends JFrame{

   public TestPaint(){
      JMenuBar bar = new JMenuBar();
      JMenu testM = new JMenu("TEST");
      testM.add(new JMenuItem("test1-child"));
      testM.add(new JMenuItem("test1-child"));

      JMenu test1M = new JMenu("TEST1");
      test1M.add(new JMenuItem("test1-child"));
      test1M.add(new JMenuItem("test1-child"));
      test1M.add(new JMenuItem("test1-child"));
      test1M.add(new JMenuItem("test1-child"));
      test1M.add(new JMenuItem("test1-child"));

      JMenu test2M = new JMenu("TEST2");
      test2M.add(new JMenuItem("test1-child"));
      test2M.add(new JMenuItem("test1-child"));
      test2M.add(new JMenuItem("test1-child"));
      test2M.add(new JMenuItem("test1-child"));
      test2M.add(new JMenuItem("test1-child"));

      JMenu test3M = new JMenu("TEST2");
      test3M.add(new JMenuItem("test1-child"));
      test3M.add(new JMenuItem("test1-child"));
      test3M.add(new JMenuItem("test1-child"));
      test3M.add(new JMenuItem("test1-child"));
      test3M.add(new JMenuItem("test1-child"));
      test3M.add(new JMenuItem("test1-child"));
      test3M.add(new JMenuItem("test1-child"));
      test3M.add(new JMenuItem("test1-child"));
      test3M.add(new JMenuItem("test1-child"));
      test3M.add(new JMenuItem("test1-child"));

      bar.add(testM);
      bar.add(test1M);
      bar.add(test2M);
      bar.add(test3M);

      setJMenuBar(bar);

      getContentPane().add(new TestPanel(), BorderLayout.CENTER);

      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      setSize(400,400);
      show();
   }

   class TestPanel extends JPanel{

      /*public void paint(Graphics g) {
         super.paint(g);
         System.out.println("paint");
         int x2 = ( int ) g.getClipBounds().getWidth();
         int y = 100;
         g.setColor( Color.RED );
         g.drawLine( 0, y, x2, y );
      }*/

      protected void paintComponent(Graphics g) {
         super.paintComponent(g);
         System.out.println("paintComponent");
         int x2 = ( int ) g.getClipBounds().getWidth();
         int y = 100;
         g.setColor( Color.RED );
         g.drawLine( 0, y, x2, y );
      }
   }
   
   public static void main(String[] args) { new TestPaint(); }
}