I cant get a filled square and a Button to be drawn at the same time!!

Question

Hello!
My problem: When I run this little program the button doesnt show until I hoover over it... and if I resize the window the square isnt drawn anymore?
why?
code:
public class TestJFrame extends JFrame{
     JButton b;
     JPanel jp;
     public TestJFrame() {
          super();
          jp = new JPanel();
          b = new JButton("button");
          jp.add(b);
          this.add(jp);
          setSize(400,400);
          setVisible(true);
     public void paint(Graphics g){
          g.setColor(Color.BLACK);
          g.fillRect(100,100,100,100);
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
TestJFrame t = new TestJFrame();
}

Answer 1

JFrame is application's main window and it is a complex and heavyweight composite container.
You should never override its painting method directly. Use one of its sub containers instead,
or, add your custom drawing panel onto it. Here's an example using JFrame's content pane
sub container and a custom panel.
import javax.swing.*;
import java.awt.*;
public class WassanJFrame extends JFrame{
  JButton b;
  WessanPanel wp;
  public WassanJFrame() {
    super();
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    wp = new WessanPanel();
    b = new JButton("button");
    wp.add(b);
    setContentPane(wp);
    setSize(400,400);
    setVisible(true);
  class WessanPanel extends JPanel{
    public void paintComponent(Graphics g){
      super.paintComponent(g);
      g.setColor(Color.BLACK);
      g.fillRect(100, 100, 100, 100);
  public static void main(String[] args) {
    new WassanJFrame();
}