How can I update components position after a setSize call?

Question

Hi there. I need some help. I have a JFrame application. When you press a button, the JFrame size changes, but the components added to it keep in the same position, they dont update to the new size, until I change manually the size of the JFrame, with the mouse. How can I make they to update automatically when I call the setSize(20,40) ?
Thank you!
The code:
public void actionPerformed( ActionEvent event )
setSize(300,90);
repaint();
}

Answer 1

Thank you Encephalopathic for your answer. I try calling revalidate() but it still doesnt work. The SSCCE is here:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Panel extends JFrame implements ActionListener {
     private JPanel panel1;
     private JPanel panel2;
     private JButton btn1;
     private JButton btn2;
        private Container container;
     public Panel(){
             super( "Title" );
            btn1 = new JButton( "Resize");
            btn2 = new JButton( "btn2");
            btn1.addActionListener(this);
            panel1 = new JPanel();
            panel2 = new JPanel();
                  panel1.add(btn1);
            panel2.add(btn2);
                  container = getContentPane();
            container.add(panel1);
            setSize(315,325);
                  setVisible(true);
     public void actionPerformed( ActionEvent event ){
               setSize(100,100);
                  container.remove(panel1);
               container.add(panel2);
                  panel2.revalidate();   // doesnt work
            container.validate(); // doesnt work
     public static void main (String args[]){
               Panel panel = new Panel();
}Edited by: gasbor on Feb 28, 2009 10:09 PM