import java.awt.*;
import javax.swing.*;

public class PanelDemo{
	public PanelDemo(){
		init();
	}
	
	public static void main(String[]args){
		new PanelDemo();
	}
	
	public void init(){
		JPanel panel = new JPanel();
		panel.setPreferredSize(new Dimension(100,300));
		JButton button = new JButton("Demo");
		button.setPreferredSize(new Dimension(100,150));
		panel.add(button);
		JFrame frame = new JFrame("Demo");
		frame.getContentPane().add(panel,BorderLayout.NORTH);
		frame.pack();
		frame.setLocationRelativeTo(null);
		frame.show();
	}
}