my button do not appear but when I resize my window the button appears

or
repaint();

I can't find revalidate() because i use component and Jframe.   In Jframe I found validate and it s Ok.  What is the diffenrence between validate, revalidate?

You should use JComponent and not Component.
For what object you use Component?
Mix of awt and swing objects is a bad idea...

s_lavie is correct, that you shouldn't mix Components and JComponents.  However, when you say you are using a Component, is this the contentPane of the JFrame (java.awt.Component->java.awt.Container)?

If so, you can create a new JPanel and set the contentPane to be the JPanel you created.

Have a look at the following code example.  It shows a JFrame and adds a button which allows you to add another button which adds others ad infinitum...

Disclaimer: this is just an example it is not production worthy code :^)

------

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;


public class AddButtonExample extends JFrame {
     
     JPanel mainPanel;
     JButton addButton;
     
     public AddButtonExample(String title) {
          super(title);
         
          addWindowListener(new WindowAdapter() {
               public void windowClosing(WindowEvent e) {
                    System.exit(0);
               }
          });
         
          mainPanel = new JPanel();
          setContentPane(mainPanel);
         
          addButton = new JButton("Add JButton");
         
          addButton.addActionListener(new ActionListener() {
               public void actionPerformed(ActionEvent e) {
                    JButton anotherButton = new JButton("Add another");
                    mainPanel.add(anotherButton);
                    anotherButton.addActionListener(this);
//                    mainPanel.repaint();
                    mainPanel.revalidate();
               }
          });
         
          mainPanel.add(addButton);
     }
     
     public static void main(String[] args) {
          AddButtonExample example = new AddButtonExample("Add Button Example");
          example.setSize(400, 200);
          example.setVisible(true);
     }
}


Note that repaint doesn't cause the new JButton to be shown - revalidate does

--
flumpman

Make the component invisible and visible

  //
  component.setVisible(false);
  component.setVisible(true);
  //

use setVisible(true), show().