Add component on JFrame during runtime (Java)

Source code below will show you how to add a component into a JFrame during program runtime. Component that will be use in this program, is JButton.

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COMPLETE SOURCE CODE FOR : AddComponentOnJFrameAtRuntime.java
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import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.JPanel;

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

import java.awt.FlowLayout;
import java.awt.BorderLayout;

public class AddComponentOnJFrameAtRuntime extends JFrame implements ActionListener
{
JPanel panel;

public AddComponentOnJFrameAtRuntime()
{
 super("Add component on JFrame at runtime");
 setLayout(new BorderLayout());
 panel=new JPanel();
 panel.setLayout(new FlowLayout());
 add(panel,BorderLayout.CENTER);
 JButton button=new JButton("CLICK HERE");
 add(button,BorderLayout.SOUTH);
 button.addActionListener(this);
 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 setSize(500,500);
 setVisible(true);
}

public void actionPerformed(ActionEvent evt)
{
 panel.add(new JButton("Button"));
 panel.revalidate();
 validate();
}

public static void main(String[]args)
{
 AddComponentOnJFrameAtRuntime acojfar=new AddComponentOnJFrameAtRuntime();
}
}

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JUST COMPILE AND EXECUTE IT
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